James Webb Space Telescope

The James Webb Space Telescope (JWST) is a space telescope that studies the universe using infrared astronomy. It is the biggest telescope in space and can see objects that are very old, distant, or too faint for the Hubble Space Telescope. This helps scientists learn about the first stars, the formation of the first galaxies, and more about potentially habitable exoplanets.

The Webb's mirror is much larger than Hubble's, but it sees infrared light, which has longer waves. This means it needs a big mirror to make clear pictures.

The Webb was launched on December 25, 2021, on an Ariane 5 rocket from Kourou, French Guiana. By January 2022, it reached its special spot near the Sun–Earth L₂ Lagrange point, about 1.5 million kilometers from Earth. Its first picture was shown to the world on July 11, 2022.

The telescope’s primary mirror is made of 18 hexagonal mirror segments coated in gold and made from beryllium. Together, they make a mirror almost 6.5 meters across—much bigger than Hubble’s. To work well, the Webb must stay very cold, below 50 K, so a special five-layer sunshield keeps it shaded from the heat of the Sun, Earth, and Moon.

Features

The James Webb Space Telescope (JWST) is much bigger than the Hubble Space Telescope. It has a 6.5-meter-diameter gold-coated primary mirror made of 18 separate pieces. This mirror can collect more light than Hubble’s mirror, so it can see objects that are very far away or very faint.

Webb is designed to look into the infrared. This helps it study very old objects in the universe, like the first stars and galaxies. It can also look at objects in our Solar System and find faint planets around faraway stars.

The telescope orbits the Sun far from Earth. This keeps it in a cool place where it can pick up faint infrared signals without interference from its own heat. The telescope’s large sunshield protects it from the heat and light of the Sun, Earth, and Moon.

Webb’s mirror is made of many pieces that fold together for launch and then unfold in space. It has special tools to take pictures and measure light from stars and galaxies. These tools help scientists learn about the universe and planets around other stars.

Comparison with other telescopes

Space telescopes can see things that ground telescopes cannot because Earth’s air blocks the view. This helps scientists find new objects in space.

Keeping a telescope cold is important for seeing heat energy from space. If a telescope gets too warm, it cannot see well. Some telescopes use special icy liquids to stay cold, but these can run out. The James Webb Space Telescope stays cold with special shields and radiators that keep its instruments at the right temperature.

Development history

For a chronological guide, see Timeline of the James Webb Space Telescope.

Background (development to 2003)

Discussions about building a telescope to follow the Hubble Space Telescope began in the 1980s. Planning started in the early 1990s. Scientists wanted a telescope that could see far back in time to the first stars and galaxies. The Hubble Space Telescope could not see these very distant objects well.

The Hubble telescope had some early problems, which led to plans for a new, better telescope. By the mid-1990s, scientists and NASA were planning a large, cold telescope that could see infrared light. This would let them look back to the early universe. In 2002, the project was named after James E. Webb, a former NASA administrator who helped start the Apollo program.

Early development and replanning (2003–2007)

The project was managed by NASA's Goddard Space Flight Center, with help from companies like Northrop Grumman and Ball Aerospace. As the project became more expensive, NASA had to change its plans. By 2005, the cost had grown so much that NASA delayed the launch and simplified some tests. Despite these changes, the main goals of the telescope stayed the same.

Detailed design and construction (2007–2021)

By 2007, the designs were ready to move forward. Over the next years, scientists built the telescope’s parts, including its huge mirror made of many small hexagons. Testing showed that some parts needed more work, which caused more delays. Finally, in 2021, the telescope was shipped to French Guiana, where it was launched into space at the end of that year.

Cost and schedule issues

The James Webb Space Telescope became much more expensive than first planned. What started as a project costing around $1 billion grew to nearly $10 billion by the time it launched in 2021. There were many reasons for the cost growth, including changes in design, unexpected problems, and delays. Despite these challenges, NASA and its partners continued to support the project.

Partnership

NASA worked with the European Space Agency (ESA) and the Canadian Space Agency (CSA) on the telescope. ESA provided some instruments and the rocket to launch the telescope, while CSA helped with the telescope’s guidance system. Thousands of people from many countries helped build and test the telescope.

Naming concerns

In 2015, some people worried that naming the telescope after James E. Webb was inappropriate because of his possible involvement in treating people unfairly during his time at NASA. NASA looked into this and found no evidence that Webb was directly involved in such actions.

Mission goals

The James Webb Space Telescope has four main goals. It wants to find light from the first stars and galaxies made after the Big Bang. It also wants to study how galaxies change over time, how stars and planets are born, and to learn about planets that might support life.

Because it looks at infrared light instead of visible light, the telescope can see older, farther, and dimmer objects than the Hubble Space Telescope. This helps scientists study the early universe and objects hidden by dust and gas. The telescope can even check if planets far away have gases like methane that might hint at life.

Ground support and operations

The Space Telescope Science Institute in Baltimore, Maryland helps run the James Webb Space Telescope. It gets data from the telescope and shares it with scientists around the world. Anyone can suggest ideas for what the telescope should look at, and a group of experts picks the best ideas each year.

The telescope sends lots of information to Earth every day. It stores data for a short time before sending it to the institute, where it is sorted and made ready for scientists to use. Even though the telescope sometimes faces tiny space particles, it keeps working well and sends us amazing pictures of space.

Launch and commissioning

Main article: Launch and commissioning of the James Webb Space Telescope

The James Webb Space Telescope was launched on December 25, 2021, aboard an Ariane 5 rocket from French Guiana. After the launch, the telescope traveled to its special place in space. It reached its final spot, called the L₂ point, on January 24, 2022.

During its trip, the telescope opened its solar panels, antennas, sunshield, and mirrors. These steps were controlled from the Space Telescope Science Institute in Baltimore, Maryland. The last step was to open the telescope's large primary mirror in early January 2022. After it reached its orbit, the telescope started aligning its mirrors to take clear pictures. By February 2022, the telescope was ready to begin its mission, capturing images of faraway stars and galaxies.

Allocation of observation time

The James Webb Space Telescope has different ways to decide who gets to use it for research. One way is through the General Observer program. Any astronomer can apply for time to use the telescope. Most of the telescope’s time is given out this way. Another way is the Guaranteed Time Observations program. This gives time to scientists who helped build parts of the telescope.

There is also a special program called the Director’s Discretionary Early Release Science program. This was used to pick 13 important science projects to observe right after the telescope finished its setup. These projects looked at many different things, like planets in our solar system, stars, and faraway galaxies. In the first round of applications, over a thousand ideas were sent in, and the telescope could only choose a fraction of them.

Scientific results

The James Webb Space Telescope started doing science work on July 11, 2022. Most data is kept private for one year for the scientists who made the observations, then it is shared with everyone.

The telescope helped scientists learn more about planets outside our solar system, the very early universe, and many other space topics. On July 12, 2022, it shared its first colorful pictures. These pictures showed stars being born, planets with water, and faraway galaxies. They showed how well the telescope can see distant and faint objects.

Later discoveries included very bright galaxies that appeared just a few hundred million years after the Big Bang. In May 2024, JWST found the farthest galaxy known, seen only 290 million years after the Big Bang. These findings help scientists understand how galaxies formed in the early universe.