In the cleanroom at Northrop Grumman, a technician inspects the bellows between the hexagonal sections that make up the large honeycomb-shaped mirror on the Webb 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.


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.

An ellipse is filled with speckled dark blue, green, and small yellow and red splotches.

This image shows the temperature fluctuations (shown as color differences) in the cosmic microwave background from a time when the universe was less than 400,000 years old. The image was captured by the Wilkinson Microwave Anisotropy Probe, or WMAP, which spent nine years, from 2001 to 2010, collecting data on the early universe. Credit: NASA | › Full image and caption | + Expand image

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.

Plumes of red stellar dust shoot out from the top and bottom of a bright central disk.

This mosaic image is the sharpest wide-angle view ever obtained of the starburst galaxy, Messier 82 (M82). The galaxy is remarkable for its bright blue disk, webs of shredded clouds and fiery-looking plumes of glowing hydrogen blasting out of its central regions.Throughout the galaxy's center, young stars are being born 10 times faster than they are inside our entire Milky Way Galaxy. Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA); Acknowledgment: J. Gallagher (University of Wisconsin), M. Mountain (STScI), and P. Puxley (National Science Foundation) | › Full image and caption | + Expand image

How Exoplanets and Our Solar System Evolve

Collage of futuristic posters depicting explorers on various exoplanets.

As we make more discoveries about exoplanets, artists at NASA are imagining what future explorers might encounter on these faraway worlds as part of the Exoplanet Travel Bureau poster series. Credit: NASA | › View and download the posters | + Expand image

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.

A sideways funnel that fans out at one end encapsulates an illustration of the history of the universe starting with the Big Bang 13.7 billion years ago through the first stars, the development of galaxies, and accelerated expansion.

An illustrated timeline of the universe. Credit: WMAP | + Expand image

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.

https://www.jpl.nasa.gov/edu/images/redshift_demo.gif

Light waves get stretched as the universe expands similar to how this ink mark stretches out as the elastic is pulled. Credit: NASA/JPL-Caltech | + Expand image

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.

A technician in a white smock stands up in a gap between several large hexagonal mirrors forming a honeycomb shape.

A technician inspects the Webb telescope's honeycomb-shaped mirror. The telescope's primary mirror is 21 feet (6.5 meters) across and is made up of 18 smaller hexagonal mirrors that must fold for launch and unfurl after the telescope reaches its orbit in space. Credit: NASA/MSFC/David Higginbotham/Emmett Given | › Full image and caption | + Expand image

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.

Colorful spirals, disks, and stars of various sizes and shapes appear against the blackness of space like sprinkles on a cake.

This image, called the Hubble Ultra Deep Field, shows 28 of the more than 500 young galaxies that existed when the universe was less than 1 billion years old. Credit: NASA, ESA, R. Bouwens and G. Illingworth (University of California, Santa Cruz) | › Full image and caption | + Expand image

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.

Technicians in white smocks stand on lifts looking at JWST's fully deployed sunshield in the cleanroom at Northrup Gruman. The five layers of the kite-shaped sunshield extend out around JWST's folded honeycomb-shaped mirror.

The sunshield is made up of five layers of specially coated material designed to block the Webb telescope's sensitive instruments from incoming heat from the Sun, Earth, and Moon. This photo, taken in the cleanroom at Northrop Grumman in Southern California in December 2020, shows the sunshield fully deployed and tensioned as it will be in space. Credit: NASA/Chris Gunn | › Full image and caption | + Expand image

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.

This animation shows how the transit method is used to hunt for planets outside our solar system. When exoplanets transit their parent star, the Webb telescope (like the Kepler space telescope, depicted here) will be able to detect the dip in the star’s brightness, providing scientists with key information about the transiting exoplanet. Students can see this technique in action with this transit math problem. Credit: NASA/JPL-Caltech | + Expand image

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.

Wispy solar flares from the Sun can be seen jutting out from a solid central circle.

This “coronagraph” image taken by the Solar and Heliospheric Observatory, or SOHO, shows dim features around our Sun. Similarly, direct images of exoplanets captured by the Webb telescope will reveal details normally washed out by the brightness of stars. Credit: ESA&NASA/SOHO | › Full image and caption | + Expand image

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.

This infographic shows the electromagnetic spectrum and how various wavelengths are used for different applications, such as infrared for remote controls.

By looking at the unique spectrum produced when the light from a star shines through the atmosphere of a transiting exoplanet, scientists can learn whether certain elements are present on that planet. Credit: NASA | + Expand image

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.

This animation shows the complex unfolding required to get the Webb telescope up and running after it arrives in orbit. | Watch on YouTube

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.

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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

  • Lyle Tavernier
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In the News

On Jan. 30, 2020, the venerable Spitzer Space Telescope mission will officially come to an end as NASA makes way for a next-generation observatory. For more than 16 years, Spitzer has served as one of NASA’s four Great Observatories, surveying the sky in infrared. During its lifetime, Spitzer detected planets and signs of habitability beyond our solar system, returned stunning images of regions where stars are born, spied light from distant galaxies formed when the universe was young, and discovered a huge, previously-unseen ring around Saturn. Read on to learn more about this amazing mission and gather tools to teach your students that there truly is more than meets the eye in the infrared universe!

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.

Infographic showing the electromagnetic spectrum and applications for various wavelengths.

This diagram shows wavelengths of light on the electromagnetic spectrum and how they're used for various applications. Image credit: NASA | + Expand image

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.

Learn more about the infrared portion of the electromagnetic spectrum and how NASA uses it to explore space. Credit: NASA/JPL-Caltech | Watch on YouTube

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.

A whisp of orange and green dust bows out beside a large blue star among a field of smaller blue stars.

The bow shock, or shock wave, in front of the giant star Zeta Ophiuchi shown in this image from Spitzer is visible only in infrared light. The bow shock is created by winds that flow from the star, making ripples in the surrounding dust. Image credit: NASA/JPL-Caltech | › Full image and caption

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.

Bursts of reds, oranges, greens, blues and violets spread out in all directions from a bright center source. Reds and oranges dominate the left side of the image.

Both NASA's Spitzer and Hubble space telescopes contributed to this vibrant image of the Orion nebula. Spitzer's infrared view exposed carbon-rich molecules, shown in this image as wisps of red and orange. Image credit: NASA/JPL-Caltech/T. Megeath (University of Toledo) & M. Robberto (STScI) | › Full image and caption

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.

A blanket of green- and orange-colored stellar dust surrounds a grouping of purple, blue and red stars.

Newborn stars peek out from beneath their natal blanket of dust in this dynamic image of the Rho Ophiuchi dark cloud from Spitzer. The colors in this image reflect the relative temperatures and evolutionary states of the various stars. The youngest stars are shown as red while more evolved stars are shown as blue. Image credit: NASA/JPL-Caltech/Harvard-Smithsonian CfA | › Full image and caption

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.

A bright band of crimson-colored dust stretches across the center of this image covered in tiny specs of light from hundreds of thousands of stars.

This Spitzer image, which covers a horizontal span of 890 light-years, shows hundreds of thousands of stars crowded into the swirling core of our spiral Milky Way galaxy. In visible-light pictures, this region cannot be seen at all because dust lying between Earth and the galactic center blocks our view. Image credit: NASA/JPL-Caltech | › Full image and caption

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.

Collage of exoplanet posters from NASA

Thanks to Spitzer, scientists are learning more and more about planets beyond our solar system. These discoveries have even inspired a series of posters created by artists at NASA, who imagined what future explorers might encounter on these faraway worlds. Image credit: NASA/JPL-Caltech | › Download posters

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:


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

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

  • Ota Lutz
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