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Scientists may soon uncover new insights about some of the most mysterious phenomena in our universe with the help of the newly launched Euclid mission. Built and managed by the European Space Agency, Euclid will use a suite of instruments developed, in part, by NASA's Jet Propulsion Laboratory to explore the curious nature of dark energy and dark matter along with their role in the expansion and acceleration of our universe.

Read on to learn how the Euclid mission will probe these cosmological mysteries. Then, find out how to use demonstrations and models to help learners grasp these big ideas.

Why It’s Important

No greater question in our universe promotes wonder in scientists and non-scientists alike than that of the origin of our universe. The Euclid mission will allow scientists to study the nearly imperceptible cosmic components that may hold exciting answers to this question.

Edwin Hubble's observations of the expanding universe in the 1920s marked the beginnings of what's now known as the big-bang theory. We've since made monumental strides in determining when and how the big bang would have taken place by looking at what's known as cosmic background radiation using instruments such as COBE and WMAP in 1989 and 2001, respectively. However, there's one piece of Hubble's discovery that still has scientists stumped: our universe is not only expanding, but as scientists discovered in 1998, that expansion is also accelerating.

This side by side comparison shows a constant rate of expansion of the universe, represented by the expanding sphere on the left, and an accelerating rate of expansion of the universe, represented by the expanding sphere on the right. Each dot on the spheres represents a galaxy and shows how galaxies move apart from each other faster in the universe that has an accelerating rate of expansion. | Watch on YouTube

How can this be? It makes intuitive sense that, regardless of the immense force of the big bang that launched all matter across the known universe 13.8 billion years ago, that matter would eventually come to a rest and possibly even start to collapse. Instead, it's as if we've dropped a glass onto the ground and discovered that the shards are flying away from us faster and faster into perpetuity.

Scientists believe that answers may lie in two yet-to-be-understood factors of our universe: dark matter and dark energy. Dark matter is unlike the known matter we experience here on Earth, such as what's found on the periodic table. We can't actually see dark matter; we can only infer its presence. It has mass and therefore gravity, making it an attractive force capable of pulling things together. Amazingly, dark matter makes up roughly 27% of the known universe compared with the much more modest 5% of "normal matter" that we experience day to day. However, dark matter is extremely dilute throughout the universe with concentrations of 105 particles per cubic meter.

In opposition to the attractive force of dark matter, we have dark energy. Dark energy is a repulsive force and makes up roughly 68% of energy in the known universe. Scientists believe that the existence of dark energy and the amount of repulsion it displays compared with dark matter is what's causing our universe to not only expand, but also to expand faster and faster.

Dr. Jennifer Wiseman, a senior project scientist with the Hubble Space Telescope mission, explains how the mission has been helping scientists learn more about dark energy. Credit: NASA Goddard | Watch on YouTube

But to truly understand this mysterious force and how it interacts with both dark matter and normal matter, scientists will have to map barely detectable distortions of light traversing the universe, carefully measuring how that light changes over time and distance in every direction. As JPL Astrophysicist Jason Rhodes explains, “Dark energy has such a subtle effect that we need to survey billions of galaxies to adequately map it.”

And that's where Euclid comes in.

How It Works

The European Space Agency and NASA each contributed to the development of the Euclid mission, which launched from Cape Canaveral Space Force Station in Florida on July 1. The spacecraft consists of a 1.2-meter (48-inch) space telescope and two science instruments: an optical camera and a near-infrared camera that also serves as a spectrometer. These instruments will provide a treasure trove of data for scientists of numerous disciplines, ranging from exoplanet hunters to cosmologists.

As Gisella de Rosa at the Space Telescope Science Institute explains, “The ancillary science topics we will be able to study with Euclid range from the evolution of the objects we see in the sky today to detecting populations of galaxies and creating catalogs for astronomers. The data will serve the entire space community.”

The cameras aboard Euclid will operate at 530-920 nanometers (optical light) and at 920-2020 nanometers (near infrared) with each boasting more than 576 million and 65 million pixels, respectively. These cameras are capable of measuring the subtle changes to the light collected from celestial objects and can determine the distances to billions of galaxies across a survey of 15,000 square degrees – one-third of the entire sky.

Meanwhile, Euclid's spectrometer will collect even more detailed measurements of the distance to tens of millions of galaxies by looking at redshift. Redshift describes how wavelengths of light change ever so slightly as objects move away from us. It is a critical phenomenon for measuring the speed at which our universe is expanding. Similar to the way sound waves change as a result of the Doppler effect, wavelengths of light are compressed to shorter wavelengths (bluer) as something approaches you and extended to longer wavelengths (redder) as it moves away from you. As determined by a Nobel Prize winning team of astronomers, our universe isn’t just red-shifting over time, distant objects are becoming redder faster.

Euclid will measure these incredibly minuscule changes in wavelength for objects near and far, providing an accurate measurement of how the light has changed as a factor of time and distance and giving us a rate of acceleration of the universe. Furthermore, Euclid will be able to map the relative densities of dark matter and normal matter as they interact with dark energy, creating unevenly distributed pockets of more attractive forces. This will allow scientists to identify minute differences in where the universe is expanding by looking at the way that light is altered or "lensed."

The multi-dimensional maps created by Euclid – which will include depth and time in addition to the height and width of the sky – will inform a complementary mission already in development by NASA, the Nancy Grace Roman Space Telescope. Launching in 2026, this space telescope will look back in time with even greater detail, targeting areas of interest provided by Euclid. The telescope will use instruments with higher sensitivity and spatial resolution to peer deeper into redshifted and faint galaxies, building on the work of Euclid to look farther into the accelerating universe. As Caltech’s Gordon Squires describes it: “We’re trying to understand 90% of our entire universe. Both of these telescopes will provide essential data that will help us start to uncover these colossal mysteries.”

Teach It

The abstract concepts of the scope and origin of our universe and the unimaginable scale of cosmology can be difficult to communicate to learners. However, simple models and simulations can help make these topics more tangible. See below to find out how, plus explore more resources about our expanding universe.

Resources

• 
  Educator Guide

  Model the Expanding Universe

  Students learn about the role of dark energy and dark matter in the expansion of the universe, then make a model using balloons.

  Subject Science

  Grades 6-12

  Time 30-60 mins

• 
  Educator Guide

  How Do We See Dark Matter?

  Students will make observations of two containers and identify differences in content, justify their claims and make comparisons to dark matter observations.

  Subject Science

  Grades 6-12

  Time Less than 30 mins

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  Educator Guide

  Math of the Expanding Universe

  Students will learn about the expanding universe and the redshift of lightwaves, then perform their own calculations with a distant supernova.

  Subject Science

  Grades 9-12

  Time 30-60 mins

• 
  Collection

  ViewSpace: Dark Energy Videos

  Use this collection of short videos to introduce learners to the concept of dark energy.

• 
  Collection

  ViewSpace: Dark Matter Videos

  Use this collection of short videos to introduce learners to the concept of dark matter.

• 
  Science Briefing

  Hubble Constant Discrepancies: Implications for Our Expanding Universe

  Hear experts discuss how the rate of the universe is measured in different cosmological epochs and what the differences in those measures can tell us.

• 
  Game

  Roman Space Observer

  How many astrophysical objects can you catch?

Explore More

• Article for Kids: What Is a Supernova?
• Article for Kids: What Is Dark Matter?
• Article: What Is Dark Energy?
• Article: Gravitational Lensing - Shining a Light on Dark Matter
• Facts & Figures: Euclid Mission - NASA
• Facts & Figures: Nancy Grace Roman Space Telescope

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NASA's Universe of Learning materials are based upon work supported by NASA under award number NNX16AC65A to the Space Telescope Science Institute, working in partnership with Caltech/IPAC, Center for Astrophysics | Harvard & Smithsonian, and the Jet Propulsion Laboratory.

TAGS: K-12 Education, Teaching, Teachers, Educators, Resources, Universe, Dark Matter, Dark Energy, Euclid, Nancy Grace Roman Space Telescope, Universe of Learning

• 

  ABOUT THE AUTHOR

  Brandon Rodriguez, Educator Professional Development Specialist, NASA-JPL Education Office

  Brandon Rodriguez is the educator professional development specialist at NASA’s Jet Propulsion Laboratory. Outside of promoting STEM education, he enjoys reading philosophy, travel and speaking to your dog like it's a person.

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Some of the wildest, most exciting features of our universe – from black holes to neutron stars – remain mysteries to us. What we do know is that because of their extreme environments, some of these emit highly energetic X-ray light, which we can detect despite the vast distances between us and the source.

Now, a NASA space telescope mission is using new techniques to not only scout out these distant phenomena, but also provide new information about their origins. Read on to learn how scientists are getting exciting new perspectives on our universe and what the future of X-ray astronomy holds.

How They Did It

In 2021, NASA launched the Imaging X-Ray Polarimeter Explorer, or IXPE, through a collaboration with Ball Aerospace and the Italian Space Agency. The space telescope is designed to operate for two years, detecting X-rays emitted from highly energetic objects in space, such as black holes, different types of neutron stars (e.g., pulsars and magnetars) and active galactic nuclei. In its first year, the telescope is focusing on roughly a dozen previously studied X-ray sources, spending hours or even days observing each target to reveal new data made possible by spacecraft's scientific instruments.

IXPE isn't the first telescope to observe the universe in X-ray light. NASA's Chandra X-ray Observatory, launched in 1999, has famously spent more than 20 years photographing our universe at a wavelength of light exclusively found in high-energy environments, such as where cosmic materials are heated to millions of degrees as a result of intense magnetic fields or extreme gravity.

Using Chandra, scientists can assign colors to the different energy levels, or wavelengths, produced by these environments. This allows us to get a picture of the highly energetic light ejected by black holes and tiny neutron stars – small, but extremely dense stars with masses 10-25 times that of our Sun. These beautiful images, such as from Chandra’s first target, Cassiopeia A (Cas A for short), show the violent beauty of stars exploding.

While Chandra has earned its name as one of “The Great Observatories,” astronomers have long desired to peer further into highly energetic environments in space by capturing them in even more detail.

IXPE expands upon Chandra’s work with the introduction of a tool called a polarimeter, an instrument used to understand the shape and direction of the light that reaches the space telescope's detectors. The polarimeter on IXPE allows scientists to gain insight into the finer details of black holes, supernovas, and magnetars, like which direction they are spinning and their three-dimensional shape.

While scientists have just begun putting IXPE's capabilities to use, they're already starting to reveal new details about the inner workings of these objects – such as the magnetic field environment around Cas A, shown in a newly released image.

“For the first time, we will use every collected photon of light to tell us about the nature and shapes of objects in the sky that would be dots of light otherwise,” says Roger Romani, a Stanford professor and the co-investigator on IXPE.

How It Works

Generally, when light is produced, it is what we call unpolarized, meaning that it oscillates in every direction. For example, our Sun produces unpolarized light. But sometimes, light is produced in a highly organized fashion, oscillating only in one direction. In astronomy, this arises when magnetic fields force particles to incredibly high speeds, creating highly organized, or polarized, light.

This is what makes objects like the supernova Cas A such enticing targets for IXPE. Exploded stars like Cas A generate massive energetic waves when they go supernova, giving scientists a view of how particles shooting out at immense speeds interact with the magnetic fields from such an event. In the case of Cas A, IXPE was able to determine that the x-rays are not very polarized, meaning the explosion created very turbulent regions with multiple field directions.

While the idea of polarized or organized light may sound abstract, you may have noticed it the last time you were outside on a sunny day. If you’ve tried on a pair of polarized sunglasses, you may have noticed that the glare was greatly reduced. That’s because as light scatters, it bounces off of reflective surfaces in all directions. However, polarized lenses have tiny filters that only allow light coming from a narrow band of directions to pass through.

The polarimeter on IXPE works in a similar way. Astronomers can determine the strength of an object's magnetic field by using the polarimeter to measure how much of the light detected by the telescope is polarized. Typically, the more polarized the light the stronger the magnetic field at the source.

Astronomers can even go a step further to measure the direction this light is oscillating by measuring the angle of the light that reaches the telescope. Because the polarized light leaves the source in a predictable fashion – namely perpendicular from its magnetic field – knowing the angle of the oscillating light provides information about the axis of rotation and potentially even the surface structure of objects such as neutron stars and nebulae.

Imagine, for example, that you were holding one end of a piece of rope secured to an object at the other end. If you swung the rope side to side to make horizontal waves, those waves would be able to make it through a narrow target like a window. If you started to shut the window from the top, narrowing the opening, the waves could conceivably still make it through the opening. However, if you made veritcal waves by waving the rope up and down, as the window closed, fewer and fewer waves would make it through the opening. Likewise, by measuring the light that makes it through the polarimeter to the detector on the other side, IXPE can determine the angle of the light received.

To collect this light, IXPE uses three identical mirrors at the end of a four meter (13 foot) boom. The light received by IXPE is carefully focused on the spacecraft’s polarimeter at the other end of the boom, allowing scientists to collect those crucial measurements.

During the IXPE launch broadcast, commentators discuss the components of the spacecraft and how it measures polarization. | Watch on YouTube

Why It's Important

Building on Chandra's observations from the past two decades, IXPE's novel approach to X-ray science is pulling the curtain back even farther on some of the most fascinating objects in the universe, providing first looks at how and where radiation is being produced in some of the most extreme environments in the universe. IXPE's measurements of Cas A are just the beginning, with even more mysterious targets ready to be explored.

Take it from Martin Weisskopf, the principal scientist on IXPE and project scientist for Chandra, who has spent his 50-year career working in X-ray astronomy, who says, “IXPE will open up the field in ways we’ve been stuck only theorizing about."

Teach It

Explore more on how NASA uses light to map our universe, and dig deeper into some of the celestial features it allows to study, such as blackholes and neutron stars.

Activities

• 
  Project

  Exploring Materials - Polarizers

  In this activity, learners experiment how polarizers affect light by using two polarizing sheets and overlapping layers of transparent tape.

• 
  Activity Guidebook

  Girls STEAM Ahead with NASA Program Cookbook

  A guidebook for facilitators planning their own Girls STEAM Ahead with NASA event using NASA’s Universe of Learning resources.

• 
  Slideshow

  Black Holes: By the Numbers

  What are black holes and how do they form? Explore more in this slideshow.

• 
  Video

  What Is a Black Hole?

  Find out how what a black hole is, how they can form and why they are so cool!

Educator Resources

• 
  Science Briefing: Exploring the High Energy Universe

  Explore the event materials from this science briefing to get a window into the most energetic processes and the most extreme objects in the universe.

  Subject Science

• 
  The Science of Color

  Quickly and easily model how colors reflect, absorb, and interact with each other in the classroom or online using your computer’s camera.

  Subject Science

  Grades 2-8

  Time < 30 mins

• 
  Using Light to Study Planets

  Students build a spectrometer using basic materials as a model for how NASA uses spectroscopy to determine the nature of elements found on Earth and other planets.

  Subject Science

  Grades 6-11

  Time 2+ hrs

• 
  Dropping In With Gravitational Waves

  Students develop a model to represent the collision of two black holes, the gravitational waves that result and the waves' propagation through spacetime.

  Subject Science

  Grades 6-8

  Time 30-60 mins

• 
  Teachable Moments

  Telescopes Get Extraordinary View of Milky Way's Black Hole

  Find out how scientists captured the first image of Sagittarius A*, why it's important, and how to turn it into a learning opportunity for students.

• 
  Teachable Moments

  How Scientists Captured the First Image of a Black Hole

  Find out how scientists created a virtual telescope as large as Earth itself to capture the first image of a black hole's silhouette.

• 
  Teachable Moments

  Gravitational Waves Detected for the First Time

  Find out how researchers proved part of Albert Einstein’s Theory of General Relativity, then create a model of the Nobel Prize-winning experiment in the classroom.

Explore More

• Article: NASA’S IXPE Helps Unlock the Secrets of Famous Exploded Star
• Educator Guide: Black Hole Math
• Opportunity: NASA/IPAC TeacherArchive Research Program
• Student Resources: Chandra
• Article: Hubble - Black Holes
• Interactive: Sagittarius A*
• Video: Hubble - Black Holes
• Website: NASA Science - Black Holes
• Download: A Galaxy Full of Black Holes Presentation
• Expert Talk: Imaging a Black Hole Lecture
• Article: Black Hole Image Makes History
• Infographic: Anatomy of a Black Hole

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NASA's Universe of Learning materials are based upon work supported by NASA under award number NNX16AC65A to the Space Telescope Science Institute, working in partnership with Caltech/IPAC, Center for Astrophysics | Harvard & Smithsonian, and the Jet Propulsion Laboratory.

TAGS: Universe, Stars and Galaxies, Space Telescope, IXPE, Astronomy, Science, Electromagnetic Spectrum, Universe of Learning

• 

  ABOUT THE AUTHOR

  Brandon Rodriguez, Educator Professional Development Specialist, NASA-JPL Education Office

  Brandon Rodriguez is the educator professional development specialist at NASA’s Jet Propulsion Laboratory. Outside of promoting STEM education, he enjoys reading philosophy, travel and speaking to your dog like it's a person.

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Our home galaxy, the Milky Way, has a supermassive black hole at its center, but we’ve never actually seen it – until now. The Event Horizon Telescope, funded by the National Science Foundation, has released the first image of our galactic black hole, Sagittarius A* (pronounced “Sagittarius A-star” and abbreviated Sgr A*).

Read on to find out how the image was acquired and learn more about black holes and Sagittarius A*. Then, explore resources to engage learners in the exciting topic of black holes.

How Black Holes Work

A black hole is a location in space with a gravitational pull so strong that nothing, not even light, can escape it. A black hole’s outer edge, called its event horizon, defines the spherical boundary where the velocity needed to escape exceeds the speed of light. Matter and radiation fall in, but they can’t get out. Because not even light can escape, a black hole is literally black. Contrary to their name’s implication, black holes are not empty. In fact, a black hole contains a great amount of matter packed into a relatively small space. Black holes come in various sizes and can exist throughout space.

We can surmise a lot about the origin of black holes from their size. Scientists know how some types of black holes form, yet the formation of others is a mystery. There are three different types of black holes, categorized by their size: stellar-mass, intermediate-mass, and supermassive black holes.

Stellar-mass black holes are found throughout our Milky Way galaxy and have masses less than about 100 times that of our Sun. They comprise one of the possible endpoints of the lives of high-mass stars. Stars are fueled by the nuclear fusion of hydrogen, which forms helium and other elements deep in their interiors. The outflow of energy from the central regions of the star provides the pressure necessary to keep the star from collapsing under its own weight.

Once the fuel in the core of a high-mass star has completely burned out, the star collapses, sometimes producing a supernova explosion that releases an enormous amount of energy, detectable across the electromagnetic spectrum. If the star’s mass is more than about 25 times that of our Sun, a stellar-mass black hole can form.

Intermediate-mass black holes have masses between about 100 and 100,000 times that of our Sun. Until recently, the existence of intermediate-mass black holes had only been theorized. NASA’s Chandra X-ray Observatory has identified several intermediate-mass black hole candidates by observing X-rays emitted by the gas surrounding the black hole. The Laser Interferometer Gravitational Wave Observatory, or LIGO, funded by the National Science Foundation, detected the merger of two stellar-mass black holes with masses 65 and 85 times that of our Sun forming an intermediate-mass black hole of 142 solar masses. (Some of the mass was converted to energy and about nine solar masses were radiated away as gravitational waves.)

Supermassive black holes contain between a million and a billion times as much mass as a stellar-mass black hole. Scientists are uncertain how supermassive black holes form, but one theory is that they result from the combining of stellar-mass black holes.

Our local galactic center’s black hole, Sagittarius A*, is a supermassive black hole with a mass of about four million suns, which is fairly small for a supermassive black hole. NASA’s Hubble Space Telescope and other telescopes have determined that many galaxies have supermassive black holes at their center.

Why They're Important

Black holes hold allure for everyone from young children to professional astronomers. For astronomers, in particular, learning about Sagittarius A* is important because it provides insights into the formation of our galaxy and black holes themselves.

Understanding the physics of black hole formation and growth, as well as their surrounding environments, gives us a window into the evolution of galaxies. Though Sagittarius A* is more than 26,000 light years (152 quadrillion miles) away from Earth, it is our closest supermassive black hole. Its formation and physical processes influence our galaxy as galactic matter continually crosses the event horizon, growing the black hole’s mass.

Studying black holes also helps us further understand how space and time interact. As one gets closer to a black hole, the flow of time slows down compared with the flow of time far from the black hole. In fact, according to Einstein’s theory of general relativity, the flow of time slows near any massive object. But it takes an incredibly massive object, such as a black hole, to make an appreciable difference in the flow of time. There's still much to learn about what happens to time and space inside a black hole, so the more we study them, the more we can learn.

How Scientists Imaged Sagittarius A*

Black holes, though invisible to the human eye, can be detected by observing their effects on nearby space and matter. As a result of their enormous mass, black holes have extremely high gravity, which pulls in surrounding material at rapid speeds, causing this material to become very hot and emit X-rays.

This video explains how Sagittarius A* appears to still have the remnants of a blowtorch-like jet dating back several thousand years. Credit: NASA | Watch on YouTube

X-ray-detecting telescopes such as NASA’s Chandra X-ray Observatory can image the material spiraling into a black hole, revealing the black hole’s location. NASA’s Hubble Space Telescope can measure the speed of the gas and stars orbiting a point in space that may be a black hole. Scientists use these measurements of speed to determine the mass of the black hole. Hubble and Chandra are also able to image the effects of gravitational lensing, or the bending of light that results from the gravitational pull of black holes or other high-mass objects such as galaxies.

To directly image the matter surrounding a black hole, thus revealing the silhouette of the black hole itself, scientists from around the world collaborated to create the Event Horizon Telescope. The Event Horizon Telescope harnesses the combined power of numerous telescopes around the world that can detect radio-wave emissions from the sky to create a virtual telescope the size of Earth.

Narrated by Caltech’s Katie Bouman, this video explains how she and her fellow teammates at the Event Horizon Telescope project managed to take a picture of Sagittarius A* (Sgr A*), a beastly black hole lying 27,000 light-years away at the heart of our Milky Way galaxy. Credit: Caltech | Watch on YouTube

In 2019, the team released the first image of a black hole's silhouette when they captured the glowing gasses surrounding the M87* galactic black hole nearly 53 million light-years (318 quintillion miles) away from Earth. The team then announced that one of their next endeavors was to image Sagittarius A*.

To make the newest observation, the Event Horizon Telescope focused its array of observing platforms on the center of the Milky Way. A telescope array is a group of telescopes arranged so that, as a set, they function similarly to one giant telescope. In addition to the telescopes used to acquire the M87* image, three additional radio telescopes joined the array to acquire the image of Sagittarius A*: the Greenland Telescope, the Kitt Peak 12-meter Telescope in Arizona, and the NOrthern Extended Millimeter Array, or NOEMA, in France.

This image of the center of our Milky Way galaxy representing an area roughly 400 light years across, has been translated into sound. Listen for the different instruments representing the data captured by the Chandra X-ray Observatory, Hubble Space Telescope, and Spitzer Space Telescope. The Hubble data outline energetic regions where stars are being born, while Spitzer's data captures glowing clouds of dust containing complex structures. X-rays from Chandra reveal gas heated to millions of degrees from stellar explosions and outflows from Sagittarius A*. Credit: Chandra X-ray Observatory | Watch on YouTube

The distance from the center of Sagittarius A* to its event horizon, a measurement known as the Schwarzschild radius, is enormous at seven million miles (12,000,000 kilometers or 0.08 astronomical units). But its apparent size when viewed from Earth is tiny because it is so far away. The apparent Schwarzschild radius for Sagittarius A* is 10 microarcseconds, about the angular size of a large blueberry on the Moon.

Acquiring a good image of a large object that appears tiny when viewed from Earth requires a telescope with extraordinarily fine resolution, or the ability to detect the smallest possible details in an image. The better the resolution, the better the image and the more detail the image will show. Even the best individual telescopes or array of telescopes at one location do not have a good enough resolution to image Sagittarius A*.

The addition of the 12-meter Greenland Telescope, though a relatively small instrument, widened the diameter, or aperture, of the Event Horizon Telescope to nearly the diameter of Earth. And NOEMA – itself an array of twelve 15-meter antennas with maximum separation of 2,500 feet (760 meters) – helped further increase the Event Horizon Telescope’s light-gathering capacity.

Altogether, when combined into the mighty Event Horizon Telescope, the virtual array obtained an image of Sagittarius A* spanning about 50 microarcseconds, or about 1/13th of a billionth the span of the night sky.

While the Event Horizon Telescope was busy capturing the stunning radio image of Sagittarius A*, an additional worldwide contingent of astronomical observatories was also focused on the black hole and the region surrounding it. The aim of the team, known as the Event Horizon Telescope Multiwavelength Science Working Group, was to observe the black hole in other parts of the electromagnetic spectrum beyond radio. As part of the effort, X-ray data were collected by NASA’s Chandra X-ray Observatory, Nuclear Spectroscopic Telescope (NuSTAR), and Neil Gehrels Swift Observatory, additional radio data were collected by the East Asian Very Long-Baseline Interferometer (VLBI) network and the Global 3 millimeter VLBI array, and infrared data were collected by the European Southern Observatory’s Very Large Telescope.

The data from these multiple platforms will allow scientists to continue building their understanding of the behavior of Sagittarius A* and to refine their models of black holes in general. The data collected from these multiwavelength observations are crucial to the study of black holes, such as the Chandra data revealing how quickly material falls in toward the disk of hot gas orbiting the black hole’s event horizon. Data such as these will hopefully help scientists better understand black hole accretion, or the process by which black holes grow.

Teach It

Check out these resources to bring the real-life STEM of black holes into your teaching, plus learn about opportunities to involve students in real astronomy research.

• 
  Educator Guide: Dropping In With Gravitational Waves

  Students develop a model to represent the collision of two black holes, the gravitational waves that result and the waves' propagation through spacetime.

  Subject Science

  Grades 6-8

  Time 30-60 mins

• 
  Teachable Moments: How Scientists Captured the First Image of a Black Hole

  Find out how scientists created a virtual telescope as large as Earth itself to capture the first image of a black hole's silhouette.

• 
  Teachable Moments: Gravitational Waves Detected for the First Time

  Find out how researchers proved part of Albert Einstein’s Theory of General Relativity, then create a model of the Nobel Prize-winning experiment in the classroom.

Explore More

Articles

• 
  Teachable Moments: Learn About the Universe With the James Webb Space Telescope

  Get a look into the science and engineering behind the largest and most powerful space telescope ever built while exploring ways to engage learners in the mission.

• 
  JPL Education ‘Teachable Moment’ Inspires Winning Science Fair Project

  A “teachable moment” turned into a science fair win for an eighth-grader in Ontario, Canada, who based his project on a classroom activity from NASA’s Jet Propulsion Laboratory.

Educator Guides

• 
  How Do We See Dark Matter?

  Students will make observations of two containers and identify differences in content, justify their claims and make comparisons to dark matter observations.

  Subject Science

  Grades 6-12

  Time < 30 mins

Student Activities

• 
  Black Holes: By the Numbers

  What are black holes and how do they form?

  Subject Science

  Grades 4-12

  Time Less than 30 mins

Check out these related resources for students from NASA’s Space Place

• What is a Black Hole?

Across the NASA-Verse

• Educator Guide: Black Hole Math
• NASA/IPAC TeacherArchive Research Program
• Student Resources: Chandra
• Articles: Hubble - Black Holes
• Audio: Sonification of the Milky Way galactic center
• Audio: Sonification of the M87 black hole
• Interactive: Sagittarius A*
• Videos: Hubble - Black Holes
• Website: NASA Science - Black Holes
• Download: A Galaxy Full of Black Holes Presentation
• Expert Talk: Imaging a Black Hole Lecture
• Article: Black Hole Image Makes History
• Graphic: Anatomy of a Black Hole

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This Teachable Moment was created in partnership with NASA’s Universe of Learning. Universe of Learning materials are based upon work supported by NASA under award number NNX16AC65A to the Space Telescope Science Institute, working in partnership with Caltech/IPAC, Center for Astrophysics | Harvard & Smithsonian, and the Jet Propulsion Laboratory.

TAGS: Black hole, Milky Way, galaxy, universe, stars, teachers, educators, lessons, Teachable Moments, K-12, science

• 

  ABOUT THE AUTHOR

  Ota Lutz, K-12 Education Group Manager, NASA-JPL Education Office

  Ota Lutz is the manager of the K-12 Education Group at NASA’s Jet Propulsion Laboratory. When she’s not writing new lessons or teaching, she’s probably cooking something delicious, volunteering in the community, or dreaming about where she will travel next.

Update: March 15, 2022 – The answers are here! Visit the NASA Pi Day Challenge slideshow to view the illustrated answer keys for each of the problems in the 2022 challenge.

In the News

No matter what Punxsutawney Phil saw on Groundhog Day, a sure sign that spring approaches is Pi Day. Celebrated on March 14, it’s the annual holiday that pays tribute to the mathematical constant pi – the number that results from dividing any circle's circumference by its diameter.

Every year, Pi Day gives us a reason to not only celebrate the mathematical wonder that helps NASA explore the universe, but also to enjoy our favorite sweet and savory pies. Students can join in the fun by using pi to explore Earth and space themselves in our ninth annual NASA Pi Day Challenge.

Read on to learn more about the science behind this year's challenge and find out how students can put their math mettle to the test to solve real problems faced by NASA scientists and engineers as we explore Earth, the Moon, Mars, and beyond!

How It Works

Dividing any circle’s circumference by its diameter gives you an answer of pi, which is usually rounded to 3.14. Because pi is an irrational number, its decimal representation goes on forever and never repeats. In 2021, a supercomputer calculated pi to more than 62 trillion digits. But you might be surprised to learn that for space exploration, NASA uses far fewer digits of pi.

Here at NASA, we use pi to understand how much signal we can receive from a distant spacecraft, to calculate the rotation speed of a Mars helicopter blade, and to collect asteroid samples. But pi isn’t just used for exploring the cosmos. Since pi can be used to find the area or circumference of round objects and the volume or surface area of shapes like cylinders, cones, and spheres, it is useful in all sorts of ways. Architects use pi when designing bridges or buildings with arches; electricians use pi when calculating the conductance of wire; and you might even want to use pi to figure out how much frozen goodness you are getting in your ice cream cone.

In the United States, March 14 can be written as 3.14, which is why that date was chosen for celebrating all things pi. In 2009, the U.S. House of Representatives passed a resolution officially designating March 14 as Pi Day and encouraging teachers and students to celebrate the day with activities that teach students about pi. And that's precisely what the NASA Pi Day Challenge is all about!

The Science Behind the 2022 NASA Pi Day Challenge

This ninth installment of the NASA Pi Day Challenge includes four brain-busters that get students using pi to measure frost deep within craters on the Moon, estimate the density of Mars’ core, calculate the water output from a dam to assess its potential environmental impact, and find how far a planet-hunting satellite needs to travel to send data back to Earth.

Read on to learn more about the science and engineering behind the problems or click the link below to jump right into the challenge.

› Take the NASA Pi Day Challenge

› Educators, get the lesson here!

Lunar Logic

NASA’s Lunar Flashlight mission is a small satellite that will seek out signs of frost in deep, permanently shadowed craters around the Moon’s south pole. By sending infrared laser pulses to the surface and measuring how much light is reflected back, scientists can determine which areas of the lunar surface contain frost and which are dry. Knowing the locations of water-ice on the Moon could be key for future crewed missions to the Moon, when water will be a precious resource. In Lunar Logic, students use pi to find out how much surface area Lunar Flashlight will measure with a single pulse from its laser.

Core Conundrum

Since 2018, the InSight lander has studied the interior of Mars by measuring vibrations from marsquakes and the “wobble” of the planet as it rotates on its axis. Through careful analysis of the data returned from InSight, scientists were able to measure the size of Mars’ liquid core for the first time and estimate its density. In Core Conundrum, students use pi to do some of the same calculations, determining the volume and density of the Red Planet’s core and comparing it to that of Earth’s core.

Dam Deduction

The Surface Water and Ocean Topography, or SWOT mission will conduct NASA's first global survey of Earth's surface water. SWOT’s state-of-the-art radar will measure the elevation of water in major lakes, rivers, wetlands, and reservoirs while revealing unprecedented detail on the ocean surface. This data will help scientists track how these bodies of water are changing over time and improve weather and climate models. In Dam Deduction, students learn how data from SWOT can be used to assess the environmental impact of dams. Students then use pi to do their own analysis, finding the powered output of a dam based on the water height of its reservoir and inferring potential impacts of this quick-flowing water.

Telescope Tango

The Transiting Exoplanet Survey Satellite, or TESS, is designed to survey the sky in search of planets orbiting bright, nearby stars. TESS does this while circling Earth in a unique, never-before-used orbit that brings the spacecraft close to Earth about once every two weeks to transmit its data. This special orbit keeps TESS stable while giving it an unobstructed view of space. In its first two years, TESS identified more than 2,600 possible exoplanets in our galaxy with thousands more discovered during its extended mission. In Telescope Tango, students will use pi to calculate the distance traveled by TESS each time it sends data back to Earth.

Teach It

Celebrate Pi Day by getting students thinking like NASA scientists and engineers to solve real-world problems in NASA Pi Day Challenge. Completing the problem set and reading about other ways NASA uses pi is a great way for students to see the importance of the M in STEM.

Pi Day Resources

• 
  Pi in the Sky Lessons

  Here's everything you need to bring the NASA Pi Day Challenge into the classroom.

  Grades 4-12

  Time Varies

• 
  NASA Pi Day Challenge

  The entire NASA Pi Day Challenge collection can be found in one, handy slideshow for students.

  Grades 4-12

  Time Varies

• 
  How Many Decimals of Pi Do We Really Need?

  While you may have memorized more than 70,000 digits of pi, world record holders, a JPL engineer explains why you really only need a tiny fraction of that for most calculations.

• 
  18 Ways NASA Uses Pi

  Whether it's sending spacecraft to other planets, driving rovers on Mars, finding out what planets are made of or how deep alien oceans are, pi takes us far at NASA. Find out how pi helps us explore space.

• 
  10 Ways to Celebrate Pi Day With NASA on March 14

  Find out what makes pi so special, how it’s used to explore space, and how you can join the celebration with resources from NASA.

• 
  Infographic: Planet Pi

  This poster shows some of the ways NASA scientists and engineers use the mathematical constant pi (3.14) and includes common pi formulas.

• 

  Downloads

  Can't get enough pi? Download this year's NASA Pi Day Challenge graphics, including mobile phone and desktop backgrounds:

  • Pi in the Sky 9 Poster (PDF, 11.2 MB)
  • Lunar Flashlight Background: Phone | Desktop
  • Mars InSight Lander Background: Phone | Desktop
  • SWOT Mission Background: Phone | Desktop
  • TESS Mission - Downlink Background: Phone | Desktop
  • TESS Mission - Science Background (not pictured): Phone | Desktop
  • Medley Background (not pictured): Phone | Desktop
• 
  Pi Day: What's Going 'Round

  Tell us what you're up to this Pi Day and share your stories and photos on our showcase page.

Plus, join the conversation using the hashtag #NASAPiDayChallenge on Facebook, Twitter, and Instagram.

Recursos en español

• 
  18 Maneras en Que la NASA Usa Pi

  Pi nos lleva lejos en la NASA. Estas son solo algunas de las formas en que pi nos ayuda a explorar el espacio.

Related Lessons for Educators

• 
  Planetary Egg Wobble and Newton's First Law

  Students try to determine the interior makeup of an egg (hard-boiled or raw) based on their understanding of center of mass and Newton’s first law of motion.

  Grades 3-8

  Time 30 min to 1 hour

• 
  Whip Up a Moon-Like Crater

  Whip up a moon-like crater with baking ingredients as a demonstration for students.

  Grades 1-6

  Time 30 min to 1 hour

• 
  Exploring Exoplanets with Kepler

  Students use math concepts related to transits to discover real-world data about Mercury, Venus and planets outside our solar system.

  Grades 6-12

  Time 30 min to 1 hour

• 
  Tracking Water Using NASA Satellite Data

  Using real data from NASA’s GRACE satellites, students will track water mass changes in the U.S.

  Grades 4-8

  Time 30 min to 1 hour

• 
  Modeling the Water Budget

  Students use a spreadsheet model to understand droughts and the movement of water in the water cycle.

  Grades 5-8

  Time 30 min to 1 hour

Related Activities for Students

• 
  NASA's Earth Minute: Mission to Earth?

  NASA doesn't just explore outer space! It studies Earth, too, with a fleet of spacecraft and scientists far and wide.

  Type Video

  Subject Science

• 
  Look at the Moon! Journaling Project

  Draw what you see in a Moon Journal and see if you can predict the moon phase that comes next.

  Type Project

  Subject Science

• 
  Mars in a Minute: Are There Quakes on Mars?

  Are there earthquakes on Mars – or rather, "marsquakes"? What could they teach us about the Red Planet?

  Type Video

  Subject Science

Explore More

Infographic

• Mars Quick Facts

Facts and Figures

• Earth's Moon
• Mars
• Earth
• Exoplanet Discoveries Dashboard

Missions and Instruments

• Mars InSight Lander
• TESS Mission
• SWOT Mission
• Lunar Flashlight

Websites

• Exoplanets Exploration
• Mars Exploration
• NASA Climate
• NASA Science: Earth's Moon
• Artemis

TAGS: Pi Day, Pi, Math, NASA Pi Day Challenge, Moon, Lunar Flashlight, Mars, InSight, Earth, Climate, SWOT, Exoplanets, Universe, TESS, Teachers, Educators, Parents, Students, Lessons, Activities, Resources, K-12

• 

  ABOUT THE AUTHOR

  Lyle Tavernier, Educational Technology Specialist, NASA-JPL Education Office

  Lyle Tavernier is an educational technology specialist at NASA's Jet Propulsion Laboratory. When he’s not busy working in the areas of distance learning and instructional technology, you might find him running with his dog, cooking or planning his next trip.

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NASA is launching the largest, most powerful space telescope ever. The James Webb Space Telescope will look back at some of the earliest stages of the universe, gather views of early star and galaxy formation, and provide insights into the formation of planetary systems, including our own solar system.

Read on to learn more about what the space-based observatory will do, how it works, and how to engage learners in the science and engineering behind the mission.

What It Will Do

The James Webb Space Telescope, or JWST, was developed through a partnership between NASA and the European and Canadian space agencies. It will build upon and extend the discoveries made by the Hubble Space Telescope to help unravel mysteries of the universe. First, let's delve into what scientists hope to learn with the Webb telescope.

A look at the James Webb Space Telescope, its mission and the incredible technological challenge this mission presents. | Watch on YouTube

How Galaxies Evolve

What the first galaxies looked like and when they formed is not known, and the Webb telescope is designed to help scientists learn more about that early period of the universe. To better understand what the Webb telescope will study, it’s helpful to know what happened in the early universe, before the first stars formed.

The universe, time, and space all began about 13.8 billion years ago with the Big Bang. For the first few hundred-thousand years, the universe was a hot, dense flood of protons, electrons, and neutrons, the tiny particles that make up atoms. As the universe cooled, protons and neutrons combined into ionized hydrogen and helium, which had a positive charge, and eventually attracted all those negatively charged electrons. This process, known as recombination, occurred about 240,000 to 300,000 years after the Big Bang.

Light that previously couldn’t travel without being scattered by the dense ionized plasma of early particles could now travel freely. The very first form of light we can look back and see comes from this time and is known as the cosmic microwave background radiation. It is essentially a map of temperature fluctuations across the universe left behind from the Big Bang. The fluxuations give clues about the origin of galaxies and the large-scale structure of galaxies. There were still no stars in the universe at this time, so the next several hundred million years are known as the cosmic dark ages.

Current theory predicts that the earliest stars were big – 30 to 300 times the size of our Sun – and burned quickly, ending in supernova explosions after just a few million years. (For comparison, our Sun has a lifespan of about 10 billion years and will not go supernova.) Observing these luminous supernovae is one of the few ways scientists could study the earliest stars. That is vital to understanding the formation of objects such as the first galaxies.

By using the Webb telescope to compare the earliest galaxies with those of today, scientists hope to understand how they form, what gives them their shape, how chemical elements are distributed across galaxies, how central black holes influence their galaxies, and what happens when galaxies collide.

Learn how the James Webb Space Telescope's ability to look farther into space than ever before will bring newborn galaxies into view. | Watch on YouTube

How Stars and Planetary Systems Form

Stars and their planetary systems form within massive clouds of dust and gas. It's impossible to see into these clouds with visible light, so the Webb telescope is equipped with science instruments that use infrared light to peer into the hearts of stellar nurseries. When viewing these nurseries in the mid-infrared – as the Webb telescope is designed to do – the dust outside the dense star forming regions glows and can be studied directly. This will allow astronomers to observe the details of how stars are born and investigate why most stars form in groups as well as how planetary systems begin and evolve.

How Exoplanets and Our Solar System Evolve

The first planet outside our solar system, or exoplanet, was discovered in 1992. Since then, scientists have found thousands more exoplanets and estimate that there are hundreds of billions in the Milky Way galaxy alone. There are many waiting to be discovered and there is more to learn about the exoplanets themselves, such as what makes up their atmospheres and what their weather and seasons may be like. The Webb telescope will help scientists do just that.

In our own solar system, the Webb telescope will study planets and other objects to help us learn more about our solar neighborhood. It will be able to complement studies of Mars being carried out by orbiters, landers, and rovers by searching for molecules that may be signs of past or present life. It is powerful enough to identify and characterize icy comets in the far reaches of our solar system. And it can be used to study places like Saturn, Uranus, and Neptune while there are no active missions at those planets.

How It Works

The Webb telescope has unique capabilities enabled by the way it views the universe, its size, and the new technologies aboard. Here's how it works.

Peering Into the Infrared

To see ancient, distant galaxies, the Webb telescope was built with instruments sensitive to light in the near- and mid-infrared wavelengths.

Light leaving these galaxies can take billions of years to reach Earth, so when we see these objects, we’re actually seeing what they looked like in the past. The farther something is from Earth, the farther back in time it is when we observe it. So when we look at light that left objects 13.5 billion years ago, we're seeing what happened in the early universe.

As light from distant objects travels to Earth, the universe continues to expand, something it’s been doing since the Big Bang. The waves that make up the light get stretched as the universe expands. You can see this effect in action by making an ink mark on a rubber band and observing how the mark stretches out when you pull on the rubber band.

What this means for light coming from distant galaxies is that the visible lightwaves you would be able to see with your eyes get stretched out so far that the longer wavelengths shift from visible light into infrared. Scientists refer to this phenomenon as redshift – and the farther away an object is, the more redshift it undergoes.

Webb telescope’s infrared sensing equipment will give scientists the chance to study some of the earliest stars that exploded in supernova events, creating the elements necessary to build planets and form life.

Gathering Light

The first stars were massive, their life cycles ending in supernova explosions. The light from these explosions has traveled so far that it is incredibly dim. This is due to the inverse square law. You experience this effect when a room appears to get darker as you move away from a light source.

To see such dim light, the Webb telescope needs to be extremely sensitive. A telescope’s sensitivity, or its ability to detect faint signals, is related to the size of the mirror it uses to gather light. On the Webb telescope, 18 hexagonal mirrors combine to form a massive primary mirror that is 21 feet (6.5 meters) across.

Compared with the Hubble Space Telescope’s eight-foot (2.4 meter) diameter mirror, this gives the Webb telescope more than six times the surface area to collect those distant particles of light known as photons. Hubble’s famous Ultra Deep Field observation captured images of incredibly faint, distant galaxies by pointing at a seemingly empty spot in space for 16 days, but the Webb telescope will be able to make a similar observation in just seven hours.

Keeping Cool

The Webb Telescope gathers its scientific data as infrared light. To detect the faint signals of objects billions of light years away, the instruments inside the telescope have to be kept very cold, otherwise those infrared signals could get lost in the heat of the telescope. Engineers accounted for this with a couple of systems designed to get the instruments cold and keep them cold.

The Webb telescope's orbit around the Sun – sitting about 1 million miles (1.5 million kilometers) from Earth at Lagrange point 2 – keeps the spacecraft pretty far from our planet's heat, but even that’s not enough. To further reduce the temperature on the instruments, the spacecraft will unfurl a tennis-court-size sunshield that will block light and heat from the Sun, Earth, and Moon using five layers of specially coated material. Each layer blocks incoming heat, and the heat that does make it through is redirected out of the sides of the sunshield. Additionally, the vacuum between each layer provides insulation.

The sunshield is so effective that the temperatures on the Sun-facing side of the telescope could be hot enough to boil water, while on the side closest to the instruments, the temperature could be as low as -394 F (-237 C, 36 K).

That’s cold enough for the near-infrared instruments to operate, but the Mid-Infrared Instrument, or MIRI, needs to be even colder. To bring down the temperature of MIRI, the Webb telescope is equipped with a special cryocooler that pumps chilled helium to the instrument to reduce its operating temperature to about -448 F (-267 C, 6 K).

Spotting Exoplanets

The Webb telescope will search for exoplanets using two different methods.

Using the transit method, the Webb telescope will look for the regular pattern of dimming that occurs when an exoplanet transits its star, or passes between the star and the telescope. The amount of dimming can tell scientists a lot about the passing exoplanet, such as the size of the planet and its distance from the star.

The second method the Webb telescope will use to search for exoplanets is direct imaging – capturing actual images of planets beyond our solar system. To enable direct imaging of exoplanets, the Webb telescope is equipped with a coronagraph. Just like you might use your hand to block a bright light, a coronagraph blocks starlight from reaching a telescope’s instruments, allowing a dim exoplanet orbiting a star to be seen.

The Webb telescope can uncover even more using spectroscopy. Light from a star produces a spectrum, which displays the intensity of light at different wavelengths. When a planet transits its star, some of the light from the star will pass through the planet's atmosphere before reaching the Webb telescope. Since all elements and molecules, such as methane and water, absorb energy at specific wavelengths, spectra from light that has passed through a planet’s atmosphere may contain dark lines known as absorption lines that tell scientists if there are certain elements present.

Using direct imaging and spectroscopy, scientists can learn even more about an exoplanet, including its color, seasons, rotation, weather, and vegetation if it exists.

All this could lead scientists to the ultimate exoplanet discovery: an Earth-size planet with an atmosphere like ours in its star’s habitable zone – a place where liquid water could exist.

Setting Up in Space

The Webb telescope will launch from French Guiana on top of an Ariane 5 rocket, a massive rocket capable of lifting the telescope, which weighs nearly 14,000 pounds (6,200 kilograms), to its destination.

The telescope's large mirror and giant sunshield are too big to fit inside the 18-foot (5.4-meter) wide rocket fairing, which protects the spacecraft during launch. To overcome this challenge, engineers designed the telescope's mirror and sunshield to fold for launch.

Two sides of the mirror assembly fold back for launch, allowing them to fit inside the fairing. The sunshield, which is 69.5 feet (21 meters) long and 46.5 feet (14 meters) wide, is carefully folded 12 times like origami so that it's narrow enough for launch. These are just two examples of several folding mechanisms needed to fit the massive telescope in its rocket for launch.

It will take about a month for the Webb telescope to reach its destination and unfurl its mirrors and sunshield. Scientists need another five months to cool down the instruments to their operating temperatures and align the mirrors correctly.

Approximately six months after launch, checkouts should be complete, and the telescope will begin its first science campaign and science operations.

Learn more and follow along with the mission from launch and unfolding to science observations and discovery announcements on the James Webb Space Telescope website.

Teach It

Check out these resources to bring the real-life STEM behind the mission into your teaching with lesson guides for educators, projects and slideshows for students, and more.

Educator Guides

• 
  Exploring the Universe - Lessons for Educators

  Teach students all about the universe, stars, galaxies, and exoplanets with this collection of standards-aligned STEM lessons.

Student Activities

• 
  All About the Universe - Activities for Students

  Students can learn all about the universe, stars, galaxies, and exoplanets with these hands-on projects, slideshows, and videos.

Articles for Students

• What is the James Webb Space Telescope?
• What is the Big Bang?
• What is a galaxy?
• What is a satellite galaxy?
• What is a transit?
• What is a black hole?
• What is a light year?
• What is a nebula?
• What is an exoplanet?
• How many solar systems are in our galaxy?
• How old are galaxies?
• What is a supernova?
• Explore the electromagnetic spectrum

Videos for Students

• Space Place in a Snap: The Solar System’s Formation
• Space Place in a Snap: Searching for Other Planets Like Ours

Resources for Educators and Parents

• James Webb Space Telescope STEM Toolkit
• Space Math @ NASA: Webb Space Telescope

Events

• Webb Space Telescope Community Events

Explore More

• Mission Website: James Webb Space Telescope
• Photos: James Webb Space Telescope
• Videos: James Webb Space Telescope
• Facts & Figures: Mid-Infrared Instrument (MIRI)

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NASA's Universe of Learning materials are based upon work supported by NASA under award number NNX16AC65A to the Space Telescope Science Institute, working in partnership with Caltech/IPAC, Center for Astrophysics | Harvard & Smithsonian, and the Jet Propulsion Laboratory.

TAGS: JWST, James Webb Space Telescope, electromagnetic spectrum, exoplanets, universe, solar system, big bang, cosmology, astronomy, star formation, galaxy, galaxies, telescope, life, technology, MIRI, Mars, Engineering, Teaching, Education, Classroom, Science, Universe of Learning

• 

  ABOUT THE AUTHOR

  Lyle Tavernier, Educational Technology Specialist, NASA-JPL Education Office

  Lyle Tavernier is an educational technology specialist at NASA's Jet Propulsion Laboratory. When he’s not busy working in the areas of distance learning and instructional technology, you might find him running with his dog, cooking or planning his next trip.

Besides providing an excuse to eat all varieties of pie, Pi Day gives us a chance to appreciate some of the ways NASA uses pi to explore the solar system and beyond. You can do the math for yourself – or get students doing it – by taking part in the NASA Pi Day Challenge. Find out below how to test your pi skills with real-world problems faced by NASA space explorers, plus get lessons and resources for educators.

How It Works

The ratio of any circle's circumference to its diameter is equal to pi, which is often rounded to 3.14. But pi is what is known as an irrational number, so its decimal representation never ends, and it never repeats. Though it has been calculated to trillions of digits, we use far fewer at NASA.

Pi is useful for all sorts of things, like calculating the circumference and area of circular objects and the volume of cylinders. That's helpful information for everyone from farmers irrigating crops to tire manufacturers to soup-makers filling their cans. At NASA, we use pi to calculate the densities of planets, point space telescopes at distant stars and galaxies, steer rovers on the Red Planet, put spacecraft into orbit and so much more! With so many practical applications, it's no wonder so many people love pi!

In the U.S., 3.14 is also how we refer to March 14, which is why we celebrate the mathematical marvel that is pi on that date each year. In 2009, the U.S. House of Representatives passed a resolution officially designating March 14 as Pi Day and encouraging teachers and students to celebrate the day with activities that teach students about pi.

The NASA Pi Day Challenge

This year's NASA Pi Day Challenge poses four puzzlers that require pi to compare the sizes of Mars landing areas, calculate the length of a year for one of the most distant objects in the solar system, measure the depth of the ocean from an airplane, and determine the diameter of a distant debris disk. Learn more about the science and engineering behind the problems below or click the link to jump right into the challenge.

› Take the NASA Pi Day Challenge
› Educators, get the lesson here!

Mars Maneuver

Long before a Mars rover touches down on the Red Planet, scientists and engineers must determine where to land. Rather than choosing a specific landing spot, NASA selects an area known as a landing ellipse. A Mars rover could land anywhere within this ellipse. Choosing where the landing ellipse is located requires compromising between getting as close as possible to interesting science targets and avoiding hazards like steep slopes and large boulders, which could quickly bring a mission to its end. In the Mars Maneuver problem, students use pi to see how new technologies have reduced the size of landing ellipses from one Mars rover mission to the next.

Cold Case

In January 2019, NASA's New Horizons spacecraft sped past Arrokoth, a frigid, primitive object that orbits within the Kuiper Belt, a doughnut-shaped ring of icy bodies beyond the orbit of Neptune. Arrokoth is the most distant Kuiper Belt object to be visited by a spacecraft and only the second object in the region to have been explored up close. To get New Horizons to Arrokoth, mission navigators needed to know the orbital properties of the object, such as its speed, distance from the Sun, and the tilt and shape of its orbit. This information is also important for scientists studying the object. In the Cold Case problem, students can use pi to determine how long it takes the distant object to make one trip around the Sun.

Coral Calculus

Coral reefs provide food and shelter to many ocean species and protect coastal communities against extreme weather events. Ocean warming, invasive species, pollutants, and acidification caused by climate change can harm the tiny living coral organisms responsible for building coral reefs. To better understand the health of Earth's coral reefs, NASA's COral Reef Airborne Laboratory, or CORAL, mission maps them from the air using spectroscopy, studying how light interacts with the reefs. To make accurate maps, CORAL must be able to differentiate among coral, algae and sand on the ocean floor from an airplane. And to do that, it needs to calculate the depth of the ocean at every point it maps by measuring how much sunlight passes through the ocean and is reflected upward from the ocean floor. In Coral Calculus, students use pi to measure the water depth of an area mapped by the CORAL mission and help scientists better understand the status of Earth's coral reefs.

Planet Pinpointer

Our galaxy contains billions of stars, many of which are likely home to exoplanets – planets outside our solar system. So how do scientists decide where to look for these worlds? Using data gathered by NASA's Spitzer Space Telescope, researchers found that they're more likely to find giant exoplanets around young stars surrounded by debris disks, which are made up of material similar to what's found in the asteroid belt and Kuiper Belt in our solar system. Sure enough, after discovering a debris disk around the star Beta Pictoris, researchers later confirmed that it is home to at least two giant exoplanets. Learning more about Beta Pictoris' debris disk could give scientists insight into the formation of these giant worlds. In Planet Pinpointer, put yourself in the role of a NASA scientist to learn more about Beta Pictoris' debris disk, using pi to calculate the distance across it.

Participate

• 
  Pi Day Challenge Lessons

  Here's everything you need to bring the NASA Pi Day Challenge into the classroom.

  Grades 4-12

  Time Varies

• 
  Slideshow: NASA Pi Day Challenge

  The entire NASA Pi Day Challenge collection can be found in one, handy slideshow for students.

  Grades 4-12

  Time Varies

• 
  Pi Day: What’s Going ’Round

  Tell us what you’re up to this Pi Day and share your stories and photos with NASA.

Join the conversation and share your Pi Day Challenge answers with @NASAJPL_Edu on social media using the hashtag #NASAPiDayChallenge

Blogs and Features

• 
  How Many Decimals of Pi Do We Really Need?

  While you may have memorized more than 70,000 digits of pi, world record holders, a JPL engineer explains why you really only need a tiny fraction of that for most calculations.

• 
  Slideshow: 18 Ways NASA Uses Pi

  Whether it's sending spacecraft to other planets, driving rovers on Mars, finding out what planets are made of or how deep alien oceans are, pi takes us far at NASA. Find out how pi helps us explore space.

Related Lessons for Educators

• 
  Rover Lessons

  Explore a collection of standards-aligned STEM lessons all about rovers.

  Grades K-12

  Time Varies

• 
  Touchdown

  Students design and build a shock-absorbing system that will protect two "astronauts" when they land.

  Grades 3-8

  Time 30 mins - 1 hr

• 
  On Target

  Students modify a paper cup so it can zip down a line and drop a marble onto a target.

  Grades 6-12

  Time 30 mins - 1 hr

• 
  Solar System Scale Models

  Explore a collection of standards-aligned STEM lessons all about the size and scale of our solar system.

  Grades 1-12

  Time Varies

• 
  Modeling an Asteroid

  Lead a discussion about asteroids and their physical properties, then have students mold their own asteroids out of clay.

  Grades 3-5

  Time 30 mins - 1 hr

• 
  Math Rocks: A Lesson in Asteroid Dynamics

  Students use math to investigate a real-life asteroid impact.

  Grades 8-12

  Time 30 mins - 1 hr

• 
  Asteroid Ace: A 'Pi in the Sky' Math Challenge

  Students use pi to calculate the rotation rate of an asteroid from another solar system in this illustrated math problem.

  Grades 11-12

  Time < 30 mins

• 
  Climate Change Lessons

  Explore a collection of standards-aligned STEM lessons all about Earth's changing climate.

  Grades K-12

  Time Varies

• 
  Using Light to Study Planets

  Students build a spectrometer using basic materials as a model for how NASA uses spectroscopy to determine the nature of elements found on Earth and other planets.

  Grades 6-11

  Time < 2 hrs

NOAA Coral Bleaching activity

• 
  Solar Sleuth: A 'Pi in the Sky' Math Challenge

  In this illustrated math problem, students use pi and data from the Kepler space telescope to find the size of a planet outside our solar system.

  Grades 6-9

  Time < 30 mins

• 
  Exploring Exoplanets with Kepler

  Students use math concepts related to transits to discover real-world data about Mercury, Venus and planets outside our solar system.

  Grades 6-12

  Time 30 mins - 1 hr

• 
  Habitable Hunt: A 'Pi in the Sky' Math Challenge

  In this illustrated math problem, students use the mathematical constant pi to find the "habitable zone" around a distant star and determine which of its planets are in that zone.

  Grades 11-12

  Time < 30 mins

Related Activities for Students

• 
  Make a Moon or Mars Rover Game

  Create a Moon or Mars exploration game using Scratch, a visual programming language. Think like NASA space-mission planners to design your game!

  Type Project

  Subject Technology

• 
  Make a Cardboard Rover

  Build a rubber-band-powered rover that can scramble across a room.

  Type Project

  Subject Engineering

• 
  Mars in a Minute: How Do You Choose a Landing Site?

  So, you want to study Mars with a lander or rover – but where exactly do you send it? Learn how scientists and engineers tackle the question of where to land on Mars in this 60-second video.

  Type Video

  Subject Engineering

• 
  Mars in a Minute: How Do You Land on Mars?

  Getting a spacecraft to Mars is one thing. Getting it safely to the ground is a whole other challenge! This 60-second video from NASA's Jet Propulsion Laboratory explains three ways to land on the surface of the Red Planet.

  Type Video

  Subject Engineering

• 
  What's That Space Rock?

  Find out how to tell the difference between asteroids, comets, meteors, meteorites and other bodies in our solar system.

  Type Slideshow

  Subject Science

• 
  Mars in a Minute: How Long is a Year on Mars?

  How long is does it take Mars to make one trip around the Sun and why is one Earth year shorter? Find out in one minute!

  Type Video

  Subject Science

• 
  Space Place in a Snap: The Solar System's Formation

  Find out how our solar system formed and how it came to be the busy place it is today.

  Type Video

  Subject Science

• 
  What Is the Kuiper Belt?

  Learn about the Kuiper Belt and some of its famous members, Kuiper Belt Objects.

  Type Article

  Subject Science

• 
  Coral Bleaching Simulator

  Adjust water temperature and pollution levels in this simulator to see what happens to a coral reef depending on the conditions you choose!

  Type Interactive

  Subject Science

• 
  Ocean Worlds

  Where might oceans – and living things – exist beyond Earth? Scientists have their eyes on these places in our own solar system.

  Type Slideshow

  Subject Science

• 
  NASA's Earth Minute: Mission to Earth?

  NASA doesn't just explore outer space! It studies Earth, too, with a fleet of spacecraft and scientists far and wide.

  Type Video

  Subject Science

• 
  NASA's Earth Minute: Earth Has a Fever

  Why is Earth getting hotter and what does that mean for us?

  Type Video

  Subject Science

NOAA Video Series: Coral Comeback

• Article: Giant Exoplanet Hunters: Look for Debris Disks
• Video: The Evolution of a Planet-Forming Disk
• Video: Birth of "Phoenix" Planets?

Multimedia

• 
  Infographic: Planet Pi

  This poster shows some of the ways NASA scientists and engineers use the mathematical constant pi (3.14) and includes common pi formulas.

• Posters: Exoplanet Travel Bureau

Facts and Figures

• Mars
• Arrokoth (2014 MU69)
• Earth
• Beta Pictoris b
• Beta Pictoris c

Missions and Instruments

• Perseverance Mars rover (Mars 2020)
• Curiosity Mars rover
• New Horizons
• CORAL
• Spitzer

Websites

• NASA Mars Exploration
• NASA Solar System Exploration
• NASA Climate Change
• NASA Exoplanets

TAGS: K-12 Education, Math, Pi Day, Pi, NASA Pi Day Challenge, Events, Space, Educators, Teachers, Parents, Students, STEM, Lessons, Problem Set, Mars 2020, Perseverance, Curiosity, Mars rovers, Mars landing, MU69, Arrokoth, New Horizons, Earth science, Climate change, CORAL, NASA Expeditions, coral reefs, oceans, Spitzer, exoplanets, Beta Pictoris, stars, universe, space telescope, Climate TM

• 

  ABOUT THE AUTHOR

  Lyle Tavernier, Educational Technology Specialist, NASA-JPL Education Office

  Lyle Tavernier is an educational technology specialist at NASA's Jet Propulsion Laboratory. When he’s not busy working in the areas of distance learning and instructional technology, you might find him running with his dog, cooking or planning his next trip.

What are you working on at JPL?

I'm working on the Spitzer Space Telescope mission. Spitzer was a telescope that was designed to observe and study the early universe. It used infrared light, which can capture images of a wide range of objects that are found in the universe. It studied and observed new galaxies, stars and exoplanets. It was launched on Aug. 25, 2003, and it was one of NASA's four Great Observatories. It was originally planned for five years, but it was extended multiple times, so it lasted for more than 16 years. We just had the end of the mission on January 30. When I started, I was working on implementing a plan to archive all the data at the end of the mission and learning about spacecraft operations. Now, I'm working on the end-of-mission closeout activities.

What was your average day like when you were working on the final days of the mission?

I didn't have an average day when I was working on the operations team. We did a lot of different tasks, so each day was different. But usually, I would meet with my mentor and co-mentor to discuss the tasks that I was working on or the timeline and deliverables for the project. I learned about mission operations for the spacecraft and the systems on the ground that support the spacecraft. The spacecraft is controlled by programmed commands that we send through various antennas on the ground. The Spitzer team would have status and coordination meetings every week. All the team leads within the project would come together and discuss updates about the spacecraft, science details and other closeout tests that needed to be completed after the mission ended.

Even though the spacecraft is no longer operational, there's still more to do on the mission. What does closing out the mission entail?

The closeout team has to archive all the information into a repository where it can be looked at later, including the information that different team members have. It could be anything from documentation to images to any records, scripts or tools that were used. Once that information has been submitted, then I go in and audit the list and make sure that all of the products that need to be delivered are there and archive them.

You got to be in mission control for Spitzer's final moments. What was that experience like?

That experience was really fun for me. We called it Spitzers' final voyage, and I was able to be a part of the operations team in mission control, monitoring the status of the spacecraft in real-time as we all said goodbye. It was amazing to see all the different team members for the Spitzer mission come together on the last day to collaborate and do all of our work at once. It was a wonderful day in history, and I was proud to be a part of it.

Have there been any other standout moments from your time at JPL?

Meeting and learning from other people at the Lab. It's very nice to be able to just reach out to someone and sit down for lunch to learn about what they do and what experiences they have. I'm able to learn a little bit about all the different things that are going on here.

You're working toward your Ph.D. at North Carolina A&T State University. What's your research focus, and what got you interested in that field?

I'm studying industrial and systems engineering. It came to my attention because it's a broad area. You can do so much with it. I wasn't quite sure what industry I wanted to go into, so that's one of the reasons that I chose it. The fact that I can work in space exploration is very cool. I know that I like to explore different areas, improve things and make things more efficient. So I thought that this would be the perfect field for me to study.

What made you interested in engineering in the first place?

I've always loved math and science, and I performed very well in those subject areas when I was in school. When it comes to new ideas, I'm very creative. So I always wondered, "What can I do with this?" A lot of my teachers mentioned that I should look into becoming an engineer, so that's what I did.

What brought you to JPL for this internship?

I heard JPL was coming to my campus – they had an info session. I was notified about it at the last minute, so I missed out. I told myself, "I should still apply even though I missed the info session." So I applied, and then I received a call and got the offer.

But I feel like there was more to what brought me here than just applying and receiving the offer. I know that the offer was based on my hard work and saying yes to the challenges and opportunities that have come my way. I've always known about JPL, but I never pictured myself actually working here. I thought that it would be challenging, and I would be coming from so far away. It was a lot all at once, but I accepted the opportunity because I wanted to be exposed to and have the experience to work in space exploration. It's an area that I'd never really thought I'd go into coming from industrial and systems engineering. Now that I have some experience in the aerospace field, I have realized how much it impacts the industry in general and the economy of this country. It's a great field for my background.

Now that you've got some experience at JPL, how has it shaped your career path?

It's provided focus for my career path. I really want to stay within this industry. It's opened my eyes to see where I can branch off and where I can contribute and apply my skills. There's so much I can do with my background just in space exploration. I'm happy that my career path went in this direction.

What did you imagine that you would be doing before you came to JPL?

I wanted to be a part of designing something to improve a process at an organization or company. I didn't really have a specific job in mind. I've always thought that I'd maybe work in the medical industry, designing and improving medical devices. I've always had a lot of different ideas of what I wanted to do. I've kind of just explored and applied to many areas that were of interest.

Now for the fun question: If, you could have any role in NASA's plans to send humans to the Moon or on to Mars, what would you want it to be?

I think that I'd want to be involved in the training process – not necessarily me going through the training, but maybe coming up with ideas or requirements to get astronauts ready to go to space efficiently and safely.

---

The laboratory’s STEM internship and fellowship programs are managed by the JPL Education Office. Extending the NASA Office of STEM Engagement’s reach, JPL Education seeks to create the next generation of scientists, engineers, technologists and space explorers by supporting educators and bringing the excitement of NASA missions and science to learners of all ages.

Career opportunities in STEM and beyond can be found online at jpl.jobs. Learn more about careers and life at JPL on LinkedIn and by following @nasajplcareers on Instagram.

TAGS: Higher Education, Internships, STEM, Engineering, Interns, College, Black History Month, Spitzer, Universe, HBCU, Women at NASA

• 

  ABOUT THE AUTHOR

  Kim Orr, Web Producer, NASA-JPL Education Office

  Kim Orr is a web and content producer for the Education Office at NASA's Jet Propulsion Laboratory. Her pastimes are laughing and going on Indiana Jones style adventures.
  

How It Worked

Human eyes can see only the portion of the electromagnetic spectrum known as visible light. This is because the human retina can detect only certain wavelengths of light through special photoreceptors called rods and cones. Everything we see with our eyes either emits or reflects visible light. But visible light is just a small portion of the electromagnetic spectrum. To "see" things that emit or reflect other wavelengths of light, we must rely on technology designed to sense those portions of the electromagnetic spectrum. Using this specialized technology allows us to peer into space and observe objects and processes we wouldn’t otherwise be able to see.

Infrared is one of the wavelengths of light that cannot be seen by human eyes. (It can sometimes be felt by our skin as heat if we are close enough to a strong source.) All objects that have temperature emit many wavelengths of light. The warmer they are, the more light they emit. Most things in the universe are warm enough to emit infrared radiation, and that light can be seen by an infrared-detecting telescope. Because Earth’s atmosphere absorbs most infrared radiation, infrared observations of space are best conducted from outside the planet's atmosphere.

So, to get a look at space objects that were otherwise hidden from view, NASA launched the Spitzer Space Telescope in 2003. Cooled by liquid helium and capable of viewing the sky in infrared, Spitzer launched into an Earth-trailing orbit around the Sun, where it became part of the agency's Great Observatory program along with the visible-light and near-infrared-detecting Hubble Space Telescope, Compton Gamma-Ray Observatory and Chandra X-ray Observatory. (Keeping the telescope cold reduces the chances of heat, or infrared light, from the spacecraft interfering with its astronomical observations.)

Over its lifetime, Spitzer has been used to detect light from objects and regions in space where the human eye and optical, or visible-light-sensing, telescopes may see nothing.

Why It's Important

NASA's Spitzer Space Telescope has returned volumes of data, yielding numerous scientific discoveries.

Vast, dense clouds of dust and gas block our view of many regions of the universe. Infrared light can penetrate these clouds, enabling Spitzer to peer into otherwise hidden regions of star formation, newly forming planetary systems and the centers of galaxies.

Infrared astronomy also reveals information about cooler objects in space, such as smaller stars too dim to be detected by their visible light, planets beyond our solar system (called exoplanets) and giant molecular clouds where new stars are born. Additionally, many molecules in space, including organic molecules thought to be key to life's formation, have unique spectral signatures in the infrared. Spitzer has been able to detect those molecules when other instruments have not.

Stars are born from condensing clouds of dust and gas. These newly formed stars are optically visible only once they have blown away the cocoon of dust and gas in which they were born. But Spitzer has been able to see infant stars as they form within their gas and dust clouds, helping us learn more about the life cycles of stars and the formation of solar systems.

Infrared emissions from most galaxies come primarily from stars as well as interstellar gas and dust. With Spitzer, astronomers have been able to see which galaxies are furiously forming stars, locate the regions within them where stars are born and pinpoint the cause of the stellar baby boom. Spitzer has given astronomers valuable insights into the structure of our own Milky Way galaxy by revealing where all the new stars are forming.

Spitzer marked a new age in the study of planets outside our solar system by being the first telescope to directly detect light emitted by these so-called exoplanets. This has made it possible for us to directly study and compare these exoplanets. Using Spitzer, astronomers have been able to measure temperatures, winds and the atmospheric composition of exoplanets – and to better understand their potential habitability. The discoveries have even inspired artists at NASA to envision what it might be like to visit these planets.

Data collected by Spitzer will continue to be analyzed for decades to come and is sure to yield even more scientific findings. It's certainly not the end of NASA's quest to get an infrared window into our stellar surroundings. In the coming years, the agency plans to launch its James Webb Space Telescope, with a mirror more than seven times the diameter of Spitzer's, to see the universe in even more detail. And NASA's Wide Field Infrared Survey Telescope, or WFIRST, will continue infrared observations in space with improved technology. Stay tuned for even more exciting infrared imagery, discoveries and learning!

Teach It

Use these lessons, videos and online interactive features to teach students how we use various wavelengths of light, including infrared, to learn about our universe:

• 
  Using Light to Study Planets

  Students build a spectrometer using basic materials as a model for how NASA uses spectroscopy to determine the nature of elements found on Earth and other planets.

  Grades 6-11

  Time > 2 hrs

• Lessons: Cool Cosmos Infrared Lessons
• Website: Cool Cosmos Infrared Primer
• Materials: Infrared Posters and Printouts

Explore More

• Article: NASA Celebrates the Legacy of the Spitzer Space Telescope
• Website: Spitzer Space Telescope Mission
• Video: Spitzer Final Voyage VR 360
• Video: Science in a Minute: The Art of Spitzer Space Telescope
• Images: Spitzer Zoomable Images
• Participate: NASA/IPAC Teacher Archive Research Program

Also, check out these related resources for kids from NASA’s Space Place:

• Infrared games, articles and activities

TAGS: Teachable Moments, science, astronomy, K-12 education, teachers, educators, parents, STEM, lessons, activities, Spitzer, Space Telescope, Missions, Spacecraft, Stars, Galaxies, Universe, Infrared, Wavelengths, Spectrum, Light

• 

  ABOUT THE AUTHOR

  Ota Lutz, K-12 Education Group Manager, NASA-JPL Education Office

  Ota Lutz is the manager of the K-12 Education Group at NASA’s Jet Propulsion Laboratory. When she’s not writing new lessons or teaching, she’s probably cooking something delicious, volunteering in the community, or dreaming about where she will travel next.

---

Accomplishing what was previously thought to be impossible, a team of international astronomers has captured an image of a black hole’s silhouette.

Evidence of the existence of black holes – mysterious places in space where nothing, not even light, can escape – has existed for quite some time, and astronomers have long observed the effects on the surroundings of these phenomena. In the popular imagination, it was thought that capturing an image of a black hole was impossible because an image of something from which no light can escape would appear completely black. For scientists, the challenge was how, from thousands or even millions of light-years away, to capture an image of the hot, glowing gas falling into a black hole.

An ambitious team of international astronomers and computer scientists has managed to accomplish both. Working for well over a decade to achieve the feat, the team improved upon an existing radio astronomy technique for high-resolution imaging and used it to detect the silhouette of a black hole – outlined by the glowing gas that surrounds its event horizon, the precipice beyond which light cannot escape. Learning about these mysterious structures can help students understand gravity and the dynamic nature of our universe, all while sharpening their math skills.

How They Did It

Though scientists had theorized they could image black holes by capturing their silhouettes against their glowing surroundings, the ability to image an object so distant still eluded them. A team formed to take on the challenge, creating a network of telescopes known as the Event Horizon Telescope, or the EHT. They set out to capture an image of a black hole by improving upon a technique that allows for the imaging of far-away objects, known as Very Long Baseline Interferometry, or VLBI.

Telescopes of all types are used to see distant objects. The larger the diameter, or aperture, of the telescope, the greater its ability to gather more light and the higher its resolution (or ability to image fine details). To see details in objects that are far away and appear small and dim from Earth, we need to gather as much light as possible with very high resolution, so we need to use a telescope with a large aperture.

That’s why the VLBI technique was essential to capturing the black hole image. VLBI works by creating an array of smaller telescopes that can be synchronized to focus on the same object at the same time and act as a giant virtual telescope. In some cases, the smaller telescopes are also an array of multiple telescopes. This technique has been used to track spacecraft and to image distant cosmic radio sources, such as quasars.

The aperture of a giant virtual telescope such as the Event Horizon Telescope is as large as the distance between the two farthest-apart telescope stations – for the EHT, those two stations are at the South Pole and in Spain, creating an aperture that’s nearly the same as the diameter of Earth. Each telescope in the array focuses on the target, in this case the black hole, and collects data from its location on Earth, providing a portion of the EHT’s full view. The more telescopes in the array that are widely spaced, the better the image resolution.

To test VLBI for imaging a black hole and a number of computer algorithms for sorting and synchronizing data, the Event Horizon Telescope team decided on two targets, each offering unique challenges.

The closest supermassive black hole to Earth, Sagittarius A*, interested the team because it is in our galactic backyard – at the center of our Milky Way galaxy, 26,000 light-years (156 quadrillion miles) away. (An asterisk is the astronomical standard for denoting a black hole.) Though not the only black hole in our galaxy, it is the black hole that appears largest from Earth. But its location in the same galaxy as Earth meant the team would have to look through “pollution” caused by stars and dust to image it, meaning there would be more data to filter out when processing the image. Nevertheless, because of the black hole’s local interest and relatively large size, the EHT team chose Sagittarius A* as one of its two targets.

The second target was the supermassive black hole M87*. One of the largest known supermassive black holes, M87* is located at the center of the gargantuan elliptical galaxy Messier 87, or M87, 53 million light-years (318 quintillion miles) away. Substantially more massive than Sagittarius A*, which contains 4 million solar masses, M87* contains 6.5 billion solar masses. One solar mass is equivalent to the mass of our Sun, approximately 2x10^30 kilograms. In addition to its size, M87* interested scientists because, unlike Sagittarius A*, it is an active black hole, with matter falling into it and spewing out in the form of jets of particles that are accelerated to velocities near the speed of light. But its distance made it even more of a challenge to capture than the relatively local Sagittarius A*. As described by Katie Bouman, a computer scientist with the EHT who led development of one of the algorithms used to sort telescope data during the processing of the historic image, it’s akin to capturing an image of an orange on the surface of the Moon.

By 2017, the EHT was a collaboration of eight sites around the world – and more have been added since then. Before the team could begin collecting data, they had to find a time when the weather was likely to be conducive to telescope viewing at every location. For M87*, the team tried for good weather in April 2017 and, of the 10 days chosen for observation, a whopping four days were clear at all eight sites!

Each telescope used for the EHT had to be highly synchronized with the others to within a fraction of a millimeter using an atomic clock locked onto a GPS time standard. This degree of precision makes the EHT capable of resolving objects about 4,000 times better than the Hubble Space Telescope. As each telescope acquired data from the target black hole, the digitized data and time stamp were recorded on computer disk media. Gathering data for four days around the world gave the team a substantial amount of data to process. The recorded media were then physically transported to a central location because the amount of data, around 5 petabytes, exceeds what the current internet speeds can handle. At this central location, data from all eight sites were synchronized using the time stamps and combined to create a composite set of images, revealing the never-before-seen silhouette of M87*’s event horizon. The team is also working on generating an image of Sagittarius A* from additional observations made by the EHT.

As more telescopes are added and the rotation of Earth is factored in, more of the image can be resolved, and we can expect future images to be higher resolution. But we might never have a complete picture, as Katie Bouman explains here (under “Imaging a Black Hole”).

To complement the EHT findings, several NASA spacecraft were part of a large effort to observe the black hole using different wavelengths of light. As part of this effort, NASA’s Chandra X-ray Observatory, Nuclear Spectroscopic Telescope Array (NuSTAR) and Neil Gehrels Swift Observatory space telescope missions – all designed to detect different varieties of X-ray light – turned their gaze to the M87 black hole around the same time as the EHT in April 2017. NASA’s Fermi Gamma-ray Space Telescope was also watching for changes in gamma-ray light from M87* during the EHT observations. If the EHT observed changes in the structure of the black hole’s environment, data from these missions and other telescopes could be used to help figure out what was going on.

Though NASA observations did not directly trace out the historic image, astronomers used data from Chandra and NuSTAR satellites to measure the X-ray brightness of M87*’s jet. Scientists used this information to compare their models of the jet and disk around the black hole with the EHT observations. Other insights may come as researchers continue to pore over these data.

Why It's Important

Learning about mysterious structures in the universe provides insight into physics and allows us to test observation methods and theories, such as Einstein’s theory of general relativity. Massive objects deform spacetime in their vicinity, and although the theory of general relativity has directly been proven accurate for smaller-mass objects, such as Earth and the Sun, the theory has not yet been directly proven for black holes and other regions containing dense matter.

One of the main results of the EHT black hole imaging project is a more direct calculation of a black hole’s mass than ever before. Using the EHT, scientists were able to directly observe and measure the radius of M87*’s event horizon, or its Schwarzschild radius, and compute the black hole’s mass. That estimate was close to the one derived from a method that uses the motion of orbiting stars – thus validating it as a method of mass estimation.

The size and shape of a black hole, which depend on its mass and spin, can be predicted from general relativity equations. General relativity predicts that this silhouette would be roughly circular, but other theories of gravity predict slightly different shapes. The image of M87* shows a circular silhouette, thus lending credibility to Einstein’s theory of general relativity near black holes.

The data also offer some insight into the formation and behavior of black hole structures, such as the accretion disk that feeds matter into the black hole and plasma jets that emanate from its center. Scientists have hypothesized about how an accretion disk forms, but they’ve never been able to test their theories with direct observation until now. Scientists are also curious about the mechanism by which some supermassive black holes emit enormous jets of particles traveling at near light-speed.

These questions and others will be answered as more data is acquired by the EHT and synthesized in computer algorithms. Be sure to stay tuned for that and the next expected image of a black hole – our Milky Way’s own Sagittarius A*.

Update: May 12, 2022 – Scientists have released the first image of Sagittarius A* captured by the Event Horizon Telescope. › Read more from Teachable Moments

Teach It

Capture your students’ enthusiasm about black holes by challenging them to solve these standards-aligned math problems.

Model black-hole interaction with this NGSS-aligned lesson:

• 
  Dropping In With Gravitational Waves

  Students develop a model to represent gravitational waves and their propagation through spacetime.

  Grades 6-8

  Time 30 mins - 1 hr

Explore More

• 
  Video: What Is a Black Hole?

  Find out how what a black hole is, how they can form and why they are so cool!

• 
  Black Holes: By the Numbers

  What are black holes and how do they form?

• 
  How Do We See Dark Matter?

  Students will make observations of two containers and identify differences in content, justify their claims and make comparisons to dark matter observations.

  Grades 6-12

  Time < 30 mins

• 
  Teachable Moment: Modeling Gravitational Waves

  Find out how researchers proved part of Albert Einstein’s Theory of General Relativity, then create a model of the Nobel Prize-winning experiment in the classroom.

• JPL News: Black Hole Image Makes History
• Graphic: Anatomy of a Black Hole

Check out these related resources for students from NASA’s Space Place

• What is a Black Hole?
• Game: Black Hole Rescue!

TAGS: Black Hole, Teachable Moments, Science, K-12 Education, Teachers, Educators, Universe

• 

  ABOUT THE AUTHOR

  Ota Lutz, K-12 Education Group Manager, NASA-JPL Education Office

  Ota Lutz is the manager of the K-12 Education Group at NASA’s Jet Propulsion Laboratory. When she’s not writing new lessons or teaching, she’s probably cooking something delicious, volunteering in the community, or dreaming about where she will travel next.