Skip to main content

NASA's James Webb Space Telescope: The ultimate guide

NASA's James Webb Space Telescope (JWST), will orbit the sun 1 million miles (1.5 million kilometers) from Earth.
NASA's James Webb Space Telescope (JWST), will orbit the sun 1 million miles (1.5 million kilometers) from Earth. (Image credit: alex-mit via Getty Images)

NASA's James Webb Space Telescope (JSWT) is an infrared space observatory that launched on Dec 25, 2021, from ESA's launch site at Kourou in French Guiana, at 7:20 a.m. EST (1220 GMT; 9:20 a.m. local time in Kourou), on board an Arianespace Ariane 5 rocket. 

The $10 billion James Webb Space Telescope — NASA's largest and most powerful space science telescope — will probe the cosmos to uncover the history of the universe from the Big Bang to alien planet formation and beyond. It is one of NASA's Great Observatories, huge space instruments that include the likes of the Hubble Space Telescope to peer deep into the cosmos. 

James Webb Space Telescope: Key facts

Launch date: Dec. 25, 2021.

Cost (at time of launch): $10 billion.

Orbit: JWST will orbit the sun, around the second Lagrange point (L2), 1 million miles (1.5 million kilometers) from Earth. 

Primary mirror size: 21.3 feet (6.5 meters) across.

Sunshield: 69.5 ft by 46.5 ft (22 meters x 12 meters).

Mass: 14,300 lbs (6,500 kg).

It will take about 30 days for the James Webb Space Telescope to travel nearly a million miles (1.5 million kilometers) to its permanent home: a Lagrange point — a gravitationally stable location in space. The James Webb Space Telescope will orbit the sun at the second Lagrange point (L2). L2 is a spot in space near Earth that lies opposite from the sun; this orbit will allow the telescope to stay in line with Earth as it orbits the sun. It has been a popular spot for several other space telescopes, including the Herschel Space Telescope and the Planck Space Observatory.  

Related: James Webb Space Telescope: An astronomer on the team explains how to send a giant telescope to space — and why

According to NASA, the James Webb Space Telescope will focus on four main areas: first light in the universe, assembly of galaxies in the early universe, birth of stars and protoplanetary systems, and planets (including the origins of life.)

Once the JWST has launched, it will undergo a series of science and calibration tests including sunshield deployment, telescope deployment, instrument turn-on and telescope alignment. According to the Space Telescope Science Institute, the best images from JWST will start to appear about six months after launch. Though we may possibly be treated to some "first light" images slightly earlier. 

The James Webb Space Telescope will undergo a series of science and calibration tests including sunshield deployment, telescope deployment, instrument turn-on and telescope alignment. (Image credit: Future)

The powerful James Webb Space Telescope is also expected to take amazing photos of celestial objects like its predecessor, the Hubble Space Telescope. Luckily for astronomers, the Hubble Space Telescope remains in good health and it's probable that the two telescopes will work together for JWST's first years. JWST will also look at exoplanets that the Kepler Space Telescope found, or follow up on real-time observations from ground space telescopes.

The James Webb Space Telescope is the product of an impressive international collaboration between NASA, the European Space Agency (ESA), and the Canadian Space Agency. According to NASA, the JWST involved over 300 universities, organizations and companies across 29 U.S. states and 14 countries. The nominal duration for the James Webb Space Telescope is five years but the goal is 10 years According to ESA.

James Webb Space Telescope science mandate

The James Webb Space Telescope's 21.3-foot (6.5 meter) diameter primary mirror. (Image credit: NASA/C. Gunn)

JWST's science mandate is principally divided among four areas:  

First light and reionization 

This refers to the early stages of the universe after the Big Bang started the universe as we know it today. In the first stages after the Big Bang, the universe was a sea of particles (such as electrons, protons and neutrons), and light was not visible until the universe cooled enough for these particles to begin combining. Another thing JWST will study is what happened after the first stars formed; this era is called "the epoch of reionization" because it refers to when neutral hydrogen was reionized (made to have an electric charge again) by radiation from these first stars.

Assembly of galaxies 

Looking at galaxies is a useful way to see how matter is organized on gigantic scales, which in turn gives us hints as to how the universe evolved. The spiral and elliptical galaxies we see today actually evolved from different shapes over billions of years, and one of JWST's goals is to look back at the earliest galaxies to better understand that evolution. Scientists are also trying to figure out how we got the variety of galaxies that are visible today, and the current ways that galaxies form and assemble.

Birth of stars and protoplanetary systems

The Eagle Nebula's "Pillars of Creation" are some of the most famous birthplaces for stars. Stars come to be in clouds of gas, and as the stars grow, the radiation pressure they exert blows away the cocooning gas (which could be used again for other stars, if not too widely dispersed.) However, it's difficult to see inside the gas. JWST's infrared eyes will be able to look at sources of heat, including stars that are being born in these cocoons.

Planets and origins of life

The last decade has seen vast numbers of exoplanets discovered, including with NASA's planet-seeking Kepler Space Telescope. JWST's powerful sensors will be able to peer at these planets in more depth, including (in some cases) imaging their atmospheres. Understanding the atmospheres and the formation conditions for planets could help scientists better predict if certain planets are habitable or not.

James Webb Space Telescope onboard instruments

The JWST will come equipped with four science instruments that will enable observations in visible, near-infrared and mid-infrared (0.6 to 28.5 micrometers) wavelengths. 

James Webb Space Telescope mission milestones

For the latest mission news and updates, check out our NASA's James Webb Space Telescope mission: Live updates page.

Thanks to a successful and precise launch on Dec. 25, 2021, NASA announced that the James Webb Space Telescope should have enough fuel to more than double its minimum mission life expectancy of 10 years. Since, its launch, the James Webb Space Telescope accomplishments just keep on coming. 

Where is the James Webb Space Telescope?

You can keep track of Webb with NASA's Where is Webb Website

An impressive HD video captured the observatory flying away from the Ariane 5 rocket that carried it into space. The three-minute video shows Webb slowly drifting away from its rocket stage and unfurling its solar panels. This video is particularly remarkable as it marks the last view we'll ever see of the James Webb Space Telescope as the observatory doesn't have any cameras onboard.  

The James Webb Space Telescope after separating from the Ariane 5 rocket that carried it into space. This is one of our last views of the impressive telescope.  (Image credit: ESA)

The James Webb Space Telescope deployed and tested a key antenna on Dec. 26, 2021, in a process that took about one hour, according to a NASA statement. The antenna will be responsible for twice-daily science data dumps to Earth. Just a day later, on Dec. 27, the observatory sailed beyond the orbit of the moon

On Dec. 31, 2021, Webb successfully unfurled its massive sunshield. The tensioning of the sunshield's five layers began on Jan, 3. 2022 and was completed the next day. The telescope's secondary mirror was then successfully deployed and latched on Jan. 5, 2022. 

Then on Jan, 8. 2022, NASA announced that the James Webb Space Telescope had successfully unfolded the giant primary mirror and is now fully deployed. The next step for Webb is the alignment of the 18 individual mirrors that make up the observatory's primary mirror. NASA estimates the work could take up to 120 days after launch for the alignment to be complete.

James Webb Space Telescope vs. Hubble Space Telescope

Comparison of the NASA/ESA Hubble Space Telescope and the NASA/ESA/CSA James Webb Space Telescope's respective mirrors. (Image credit: Future/Adrian Mann)

The James Webb Space Telescope is referred to as the successor of the Hubble Space Telescope. 

Scientific advancement is all about "standing on the shoulders of giants" and the JWST will do just that, as its scientific goals were motivated by the results from Hubble.

The two space telescopes have different capabilities, whilst Hubble primarily observed the cosmos in optical and ultraviolet wavelengths (with some infrared capabilities.) The JWST will primarily look at the universe in infrared. Due to the expansion of the universe, light from distant objects shifts to longer wavelengths at the redder end of the spectrum — known as redshifted, according to ESA. The JWST will observe this infrared light in great detail and shed light on some of the oldest stars and galaxies in the universe.

Another big difference between the James Webb Space Telescope and the Hubble Space Telescope is that JWST will orbit the sun, whilst Hubble orbits Earth. JWST will be too far away to be serviced, unlike Hubble which was accessed and serviced by space shuttle missions.

James Webb Space Telescope delays

Good things come to those who wait.

 The JWST was first slated to fly in 2007 and since then astronomers' patience has been sternly tested. A mix of engineering problems, political hesitancy and project management issues have all contributed to countless delays. 

In July 2011, U.S. politicians threatened to pull funding for the JWST. After a nail-biting few months, the spacecraft was saved in November 2011. Then in March 2018, the launch of JWST was delayed due to technical issues with the spacecraft. Later that year in June, an independent review board recommended the launch to be moved to March 2021. 

In 2020, The global coronavirus (COVID–19) pandemic impacted JWST's progress and in July 2020, NASA announced a new launch date of October 31, 2021. Despite the perseverance and determination of the JWST team during a difficult time, the delays kept coming. 

In June 2021, problems with the Ariane 5 launch vehicle pushed the launch date back to November or possibly early December 2021. Then in September NASA and ESA announced yet another delay as the observatory had not yet been shipped from its original location in California to ESA's launch site at Kourou in French Guiana. The two agencies announced a new launch date of Dec.18, but bad weather soon put a stop to that. 

Finally, the JWST successfully launched on Dec 25, 2021, from ESA's launch site at Kourou in French Guiana, at 7:20 a.m. EST (1220 GMT; 9:20 a.m. local time in Kourou), on board an Arianespace Ariane 5 rocket. 

The controversial naming of the James Webb Space Telescope

The space telescope was previously known as the Next Generation Space Telescope and was renamed the James Webb Space Telescope in Sept. 2002. 

The JWST is named for former NASA chief James Webb. Webb took charge of the space agency from 1961 to 1968, retiring just a few months before NASA put the first man on the moon.

Although Webb's tenure as NASA administrator is most closely associated with the Apollo moon program, he is also considered a leader in space science. Even in a time of great political turmoil, Webb set NASA's science objectives, writing that launching a large space telescope should be a key goal of the space agency. 

NASA launched more than 75 space science missions under Webb's guidance. They included missions that studied the sun, stars and galaxies as well as space directly above Earth's atmosphere.

Not everyone is happy with the choice of name for the space telescope. An online petition was set up by critics urging NASA to rename the telescope due to claims that Webb was complicit in discrimination against gay and lesbian NASA employees during his tenure. NASA has since said it will not rename the telescope despite complaints.

Additional resources

You can learn how the JWST is designed to answer some of the biggest questions in the universe with the UK Space Agency and explore it's impressive mirrors with NASA. Keep yourself and others entertained with these fun facts and a folding puzzler from Northrop Grumman. 


Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at:

Elizabeth Howell

Elizabeth Howell, Ph.D., is a contributing writer for since 2012. As a proud Trekkie and Canadian, she tackles topics like spaceflight, diversity, science fiction, astronomy and gaming to help others explore the universe. Elizabeth's on-site reporting includes two human spaceflight launches from Kazakhstan, and embedded reporting from a simulated Mars mission in Utah. She holds a Ph.D. and M.Sc. in Space Studies from the University of North Dakota, and a Bachelor of Journalism from Canada's Carleton University. Her latest book, NASA Leadership Moments, is co-written with astronaut Dave Williams. Elizabeth first got interested in space after watching the movie Apollo 13 in 1996, and still wants to be an astronaut someday.