James Webb Space Telescope (JWST)

The James Webb Space Telescope (JWST) is a state-of-the art space observatory launched into Earth’s orbit by the National Aeronautics and Space Administration (NASA) in 2021. The telescope is the most powerful space observatory ever launched by NASA and features a mirror 21.3 feet (6.5 meters) across. The JWST detects light emitted in the infrared bands of the spectrum, which allows it to see through clouds of interstellar dust and observe distant space objects. The main goals of the telescope are to gather information on the Big Bang and the early universe, detect ancient galaxies, and observe planets both in our solar system and those orbiting other stars. Within a few months of its launch, the telescope began providing stunning images of the cosmos. Among its first accomplishments were the discovery of the most distant galaxy every observed up to that point in time and highly detailed images of the planet Jupiter.

Background

Since the first telescopes were invented in the seventeenth century, Earth-based astronomers have had to deal with one common problem. The thickness and turbulent motion of the planet’s atmosphere limits the resolution of ground-based telescopes. This phenomenon is easily observable by noticing how stars seem to “twinkle” in the night sky. Furthermore, cloud cover, temperature variations, and light pollution can also negatively impact ground-based viewing.

The idea of placing a telescope into space—above the turbulent atmosphere—was first suggested in the 1920s and later theorized in the 1940s. In 1968, NASA launched the first successful space telescope, known as Orbital Astronomical Observatory 2 (OAO-2), which examined the sky in the ultraviolet frequency of light. The OAO-2 and its successors made several important astronomical discoveries and also provided a blueprint for future space-based telescopes.

NASA had been discussing the creation of a large space-based telescope as early as the late 1960s and developed the project during the 1970s. The observatory was named the Hubble Space Telescope after Edwin Hubble, an early twentieth-century astronomer who was the first to observe distant galaxies and discovered the universe was far larger than the Milky Way. The Hubble Space Telescope was launched in 1990, and after a repair mission to fix a faulty mirror in 1993, began sending back the most detailed images of the universe ever seen. During its more than three decades in orbit, the Hubble has made more than one million observations. Among its more notable accomplishments were observing how planets form, discovering the existence of supermassive black holes at the center of most galaxies, and placing the age of the universe at 13.8 billion years.

Overview

Just six years after Hubble’s launch, NASA scientists officially proposed that the agency develop a space-based telescope that could observe the universe through infrared light. Hubble had primarily focused on ultraviolet light and light in the visible spectrum. Every object in the universe emits some level of infrared light, or heat energy. A telescope designed to detect the infrared can “see” through clouds of interstellar dust that can scatter visible light. They can also detect heat energy emitted from distant galaxies, stars, and planets that would be too faint to be detected by other telescopes.

The project received funding in the late 1990s with research and development work getting underway in 2002. The telescope was named after James E. Webb, the director of NASA from 1961 to 1968. Webb headed the agency during the height of the Space Race and the creation of the Apollo Program that would ultimately land astronauts on the moon in 1969. Webb had been a strong proponent of space flight for scientific purposes was an early supporter of placing a telescope in space.

The physical construction of the JWST began in 2004, and by 2011, the telescope’s main mirror was completed. Additional mirrors and scientific instruments were added to the telescope, which went through years of rigorous testing, culminating in its final test in 2020.

Completed at a cost of $10 billion, the JWST weighs about 14,300 pounds (6,500 kilograms). Its primary mirror measures 21.3 feet (6.5 meters) wide and consists of eighteen gold-plated hexagonal segments. To protect the telescope from the sun’s heat, the JWST also has a large sunshield that measures 69.5 feet by 46.5 feet (21 meters by 14 meters). The telescope must be kept extremely cold to detect infrared radiation. The sunshield keeps the telescope’s temperature at about -370 Fahrenheit (-233 Celsius).

The JWST was launched aboard an Ariane 5 rocket on Christmas Day 2021 from the European Space Agency’s (ESA) Guiana Space Centre in South America. During the next two weeks, the telescope unfurled its primary antenna, sunshield, secondary mirror, and primary mirror. On January 24, 2022, the telescope reached its gravitationally stable orbit point about one million miles (1.6 million kilometers) from Earth.

NASA scientists spent about a month and a half aligning the eighteen sections on the telescope’s primary mirror, finishing the procedure in mid-March. By May, the remaining instruments and secondary mirrors were tested and aligned. The telescope became fully operational on July 11, 2022.

That same day, NASA released the first photos taken by the telescope. Among them was an image of a cluster of galaxies called SMACS 0723. The photo was taken in a small patch of sky in the constellation Volans, a star pattern viewable in the southern hemisphere. It features thousands of galaxies in a single frame. The image was a snapshot of the early universe, showing the galaxies as they existed just a few hundred million years after the Big Bang, the sudden cosmic expansion that created the universe. The galaxies in SMACS 0723 were the most distant objects ever photographed in high-definition infrared. The gravity from the cluster was so strong that it bent and magnified the light from more distant galaxies behind it, bringing them into view.

The images and data recorded by the JWST triggered a series of groundbreaking discoveries, including several candidates for the most-distant galaxy ever recorded. In April 2022, Earth-based astronomers detected a galaxy called HD 1, which was 13.5 billion light years away. A light year is the distance light travels in a year, meaning astronomers were viewing HD 1 as it looked 13.5 billion years ago, just 330 million years after the Big Bang. After the JWST began sending its data, that record was broken by a galaxy named GLASS-z13, which was observed about three hundred million years after the Big Bang. In August 2022, the JWST revealed an even more distant galaxy, CEERS-93316, which was observed about 235 million years after the big bang.

In addition to peering back into the earliest days of the universe, the JWST’s mission also includes observing planets orbiting other stars in our galaxy. On one of those planets, named WASP-96 b, the telescope found the unmistakable signature of water in its atmosphere. The planet is a large, hot world orbiting a star 1,150 light years away. With a temperature topping out at 1000 degrees Fahrenheit (538 Celsius), the planet’s water is relegated to clouds and haze in its upper atmosphere.

The infrared capabilities of the telescope also allowed astronomers to see through the clouds of gas and dust that swirl about star-forming regions in the galaxy NGC 7496. They were able to view bright streams of gas and dust within the galaxy where stars were actively forming. Astronomers hope that the telescope will eventually reveal the exact moment that the collapsing clouds of gas and dust begin nuclear fusion and “turn on” to become stars.

The high-definition images from the telescope proved so sharp that astronomers were able to see a distant galaxy “hidden” behind the Southern Ring Nebula, an interstellar cloud of glowing gas and dust about 2,500 light years away. Previously, the galaxy was lost amid the gas and dust and mistakenly seen as part of the nebula.

Closer to home, the JWST also turned its attention to the planet Jupiter in our own solar system. The images provided sharp detail of the planet’s swirling atmosphere, including its Great Red Spot, a large storm that could easily engulf Earth. The telescope’s infrared equipment was able to detect Jupiter’s hot upper atmosphere, which appeared as a red ring. It was also able to study the auroras at the planet’s north and south poles, its ring system, and two of its smallest moons: Amalthea and Adrastea.

In the years after it became operational, the JWST continued offering scientists glimpses at previously unseen parts of the universe, as well as providing fresh views of well-known objects in space. In May 2024, for example, NASA announced that the JWST had found the most distant known galaxy in the universe at that time. This discovery was part of an effort by scientists to use the JWST to better understand the period of time known as the Cosmic Dawn, a term referring to the first hundreds of millions of years after the Big Bang. That same month, the JWST also detected the most distant known merger of black holes.

The JWST was originally conceived as a replacement for the Hubble Space Telescope, but with the Hubble still in operation during the years shortly after the JWST's launch, the two space observatories were expected to collaborate on projects for a few years. The minimum lifespan of the JWST was set at five years, but NASA had set a goal of ten years prior to launch. However, the launch and deployment of the observatory was so efficient that NASA, during the early 2020s, was optimistic that the JWST would operate for at least two decades.

Bibliography

“About—The Hubble Story.” National Aeronautics and Space Administration, 26 May 2022, www.nasa.gov/content/about-the-hubble-story. Accessed 24 Aug. 2022.

Beall, Abigail. “The James Webb Space Telescope (JWST).” New Scientist, 2022, www.newscientist.com/definition/james-webb-space-telescope-jwst/. Accessed 24 Aug. 2022.

Howell, Elizabeth, and Daisy Dobrijevic. “NASA’s James Webb Space Telescope: The Ultimate Guide.” Space.com, 12 July 2022, www.space.com/21925-james-webb-space-telescope-jwst.html. Accessed 15 Jul. 2024.

O’Callaghan, Jonathan. “Two Weeks In, the Webb Space Telescope Is Reshaping Astronomy.” Quanta, 25 July 2022, www.quantamagazine.org/two-weeks-in-the-webb-space-telescope-is-reshaping-astronomy-20220725/. Accessed 24 Aug. 2022.

Sanders, Robert. “Surprising Details Leap Out in Sharp New James Webb Space Telescope Images of Jupiter.” Phys.org, 22 Aug. 2022, phys.org/news/2022-08-sharp-james-webb-space-telescope.html. Accessed 24 Aug. 2022.

“Webb Project History.” Webb Space Telescope, 2021, webbtelescope.org/webb-science/the-observatory/mission-timeline. Accessed 24 Aug. 2022.

“Webb Space Telescope.” National Aeronautics and Space Administration, 2024, webb.nasa.gov/. Accessed 15 Jul. 2024.

“Webb vs Hubble Telescope.” National Aeronautics and Space Administration, 2024, jwst.nasa.gov/content/about/comparisonWebbVsHubble.html. Accessed 15 Jul. 2024.

“Who Is James Webb?” National Aeronautics and Space Administration, www.jwst.nasa.gov/content/about/faqs/whoIsJamesWebb.html. Accessed 24 Aug. 2022.