James Webb Space Telescope (2021): Launch and First Images

The James Webb Space Telescope (JWST) was launched on 25 December 2021 from French Guiana, the largest and most complex telescope ever sent into space. A joint project of NASA, the European Space Agency (ESA) and the Canadian Space Agency (CSA), it unfolded itself on the way to an orbit 1.5 million km from Earth. Its first images, released in July 2022, showed the universe in unprecedented infrared detail and began a new era in astronomy.

Background: a successor to Hubble

Planning began in the mid-1990s, a few years after the Hubble Space Telescope was launched. A 1996 report on the future of astronomy recommended a large infrared telescope to study the first galaxies, which formed a few hundred million years after the Big Bang.

Light from such distant galaxies is stretched to longer, redder wavelengths by the expansion of the universe, first measured by Edwin Hubble. By the time it reaches us, much of it is infrared, which a telescope must observe from space. Infrared also passes through dust clouds, revealing stars and planets in formation.

The project, first called the Next Generation Space Telescope, was renamed in 2002 after James E. Webb, who led NASA from 1961 to 1968 during the Apollo programme. The Nobel laureate John Mather served as its senior project scientist.

Design challenges

Webb’s primary mirror is 6.5 metres across, more than twice the diameter of Hubble’s. Too large to fit inside any rocket fairing in one piece, it is made of 18 hexagonal segments of beryllium coated with a thin layer of gold, which reflects infrared light well. The mirror had to fold up for launch and unfold in space.

An infrared telescope must be very cold so its own heat does not swamp faint signals. Webb is shielded from the Sun, Earth and Moon by a five-layer sunshield about the size of a tennis court, made of a thin plastic film called Kapton. The cold side sits below about 50 kelvin (around minus 223 °C), and one instrument, MIRI, is cooled further by a cryocooler to about 7 kelvin.

The telescope carries four main instruments. NIRCam, its main camera, was built by the University of Arizona and Lockheed Martin. ESA provided the NIRSpec spectrograph and, with NASA, the MIRI mid-infrared instrument. Canada supplied the Fine Guidance Sensor and the NIRISS instrument.

Delays and cost

When early planning began, a launch around 2007 and a cost near 1 billion US dollars were envisaged. As engineers faced the difficulty of the design, the launch date slipped repeatedly and costs grew. In 2011 a US House of Representatives subcommittee proposed cancelling the project; Congress instead kept it alive under a cost cap of about 8 billion dollars for development.

Further delays followed, including problems during testing of the sunshield and the 2020 COVID-19 pandemic. NASA’s total lifecycle cost reached about 10 billion dollars, making JWST one of the most expensive science projects ever undertaken.

Launch and deployment

As part of its contribution, ESA provided the launch on an Ariane 5 rocket from Europe’s Spaceport at Kourou in French Guiana. After small additional delays for a clamp-band incident during preparations and a communications issue, the rocket lifted off at 12:20 UTC on 25 December 2021.

The launch was so precise that the telescope needed less fuel than planned for course corrections, leaving enough to extend its potential operating life well beyond the 10-year goal, possibly to around 20 years.

Over the following two weeks, Webb went through a deployment sequence with hundreds of steps, each a potential single point of failure. The sunshield was unfolded and tensioned by 4 January 2022, and the primary mirror wings locked into place on 8 January. On 24 January the telescope entered its orbit around the second Sun-Earth Lagrange point (L2), about 1.5 million km from Earth on the side away from the Sun.

Engineers then spent months cooling the instruments, aligning the 18 mirror segments to act as a single surface and calibrating the instruments.

Day-to-day operations are run from the Space Telescope Science Institute in Baltimore, Maryland, which also operates Hubble. Observing time is awarded through an annual competition open to astronomers worldwide, with European and Canadian scientists guaranteed a share in return for their agencies’ contributions. The first cycle of science observations began in July 2022.

First images

On 11 July 2022 US President Joe Biden released Webb’s first full-colour image, often called Webb’s First Deep Field. It showed the galaxy cluster SMACS 0723 and, magnified by its gravity, thousands of more distant galaxies, captured in about 12.5 hours of observation.

The next day NASA and its partners released more images and data: the Carina Nebula’s “cosmic cliffs” of star formation, the galaxy group Stephan’s Quintet, the Southern Ring Nebula, and a spectrum showing water vapour in the atmosphere of the giant exoplanet WASP-96 b.

Since then Webb has identified some of the most distant galaxies ever observed, studied the atmospheres of planets around other stars and examined objects in our own Solar System. Its discovery of unexpectedly bright and massive early galaxies has prompted debate about how quickly galaxies formed.

Webb and Hubble compared

Webb is often described as Hubble’s replacement, but the two telescopes are complementary and operated side by side after 2022. Hubble observes mainly visible and ultraviolet light, with some near-infrared capability, while Webb is optimised for infrared wavelengths from about 0.6 to 28 micrometres.

The great distance of L2 keeps Webb cold and gives it a steady view away from the Sun, but it also means that, unlike Hubble, it could not be repaired if something went wrong. That is one reason the deployment in early 2022 was watched so anxiously.

The naming debate

From 2021 some astronomers argued that the telescope should be renamed, because James Webb had held senior government posts during the “Lavender Scare”, when gay and lesbian employees were dismissed from US federal service. NASA commissioned a historical investigation, published in 2022, which found no evidence that Webb had led or advocated those firings. The agency kept the name, although the debate continued among some scientists.

Timeline

• 1996: A report recommends a large infrared space telescope as Hubble’s successor.
• 2002: The Next Generation Space Telescope is named after James E. Webb.
• 2011: A House subcommittee proposes cancellation; the project survives under a cost cap.
• 2021, 25 December: JWST launches on an Ariane 5 from Kourou.
• 2022, 8 January: Deployment of the primary mirror is completed.
• 2022, 24 January: Webb arrives at its orbit around the L2 point.
• 2022, 11 July: The first full-colour image, of SMACS 0723, is released.
• 2022, 12 July: Further first images and spectra are published.

Why it matters

The James Webb Space Telescope lets astronomers look back to the era of the first galaxies, peer through dust into stellar nurseries and analyse the atmospheres of distant worlds. Its successful launch and flawless deployment, after decades of delays and doubts, also showed what international cooperation in science can achieve, continuing a line of astronomical tools that stretches back to Galileo’s first telescope.