The James Webb Space Telescope (JWST), also referred to as the Webb, is a space-based observatory optimized for infrared wavelengths to study galaxy, star, and planet formation in the universe. JWST was designed as the successor to the Hubble space telescope, using new technologies that complement and extend Hubble's discoveries. JWST has a longer wavelength coverage (0.6 to 28 micrometers, ranging from visible orange-colored to mid-infrared) and greater sensitivity (primary mirror area of 25m2) compared to Hubble. It also operates farther away from Earth, orbiting at Lagrange point 2, 1.5 million km from Earth. These combine to allow JWST to look further back into the early universe and deep into dust clouds where stars and planets are formed.
The JWST mission has four primary science goals:
- Search for and study the first galaxies or light-emitting objects that formed after the Big Bang
- Study how galaxies evolved from their formation until the present
- Observe the first stages of star formation, their evolution, and how planetary systems form
- Measure the physical and chemical properties of planetary systems outside of the solar system and investigate the potential for life in those systems
Detecting the very first galaxies and luminous objects requires observing objects with a redshift between 15 and 30, i.e., where spectral features have shifted to sixteen times or more than their original wavelength. At those redshifts, ultraviolet light is shifted into the infrared range, the wavelengths JWST is optimized for. These objects correspond to only 100 to 250 million years after the Big Bang, meaning the light JWST hopes to detect traveled a distance of 13.6 billion light-years.
JWST has to overcome significant engineering challenges to deliver these scientific goals, particularly building a large enough mirror to capture enough light and keeping it cold to reduce unwanted sources of infrared light that can interfere with the light being observed. JWST has a 25m2 mirror broken down into eighteen segments. The mirror is 6.5 meters (21.3 feet) at its widest point. The mirror and its sunshield had to be unfolded in space as it would not survive launch unfurled.
Details on JWST's wavelength range, mirror size, and location.
JWST has four instruments, each designed to study different aspects of infrared light:
- Near-Infrared Camera (NIRCam)
- Near-Infrared Spectrograph (NIRSpec)
- Mid-Infrared Instrument (MIRI) with camera and spectrograph
- Near-Infrared Image and Slitless Spectrograph (NIRISS)
JWST is a collaboration between fourteen countries with NASA as the lead partner, responsible for the mission and significant contributions from the European Space Agency (ESA) and the Canadian Space Agency (CSA). These countries include Austria, Belgium, Canada, Denmark, France, Germany, Ireland, Italy, the Netherlands, Spain, Sweden, Switzerland, the United Kingdom, and the United States of America. NASA's main industrial contractor was Northrop Grumman, responsible for building the optical telescope, spacecraft bus, and sunshield, as well as preparing the observatory for launch. Northrop Grumman led a team that included two major sub-contractors, Ball Aerospace and Harris (formerly ITT-Exelis). Three principal subcontractors developed the beryllium mirror Coherant (formerly Tinsley Laboratories), General Dynamics Global Imaging Technologies (formerly Axsys Technologies), and Materion (formerly Brush Wellman Inc.). The launch vehicle and launch services were provided by ESA. All of the near-infrared detectors were supplied by Teledyne Technologies, Inc.
The mission partners responsible for each instrument were the following:
- Mid-Infrared Instrument (MIRI)—provided by a consortium of European countries, the European Space Agency (ESA), and the NASA Jet Propulsion Laboratory (JPL) with detectors from Raytheon Vision Systems
- Near-Infrared Spectrograph (NIRSpec)—provided by ESA
- Near-Infrared Camera (NIRCam)—built by the University of Arizona working with Lockheed-Martin
- Near-Infrared Imager and Slitless Spectrograph (NIRISS)—provided by the Canadian Space Agency (CSA)
The JWST launch on December 25, 2021.
The mission launched on an Ariane 5 rocket from Europe's Spaceport in French Guiana, located in South America. The launch date was on December 25, 2021. The launch segment has three primary components:
- Launch vehicle—Ariane 5 with the cryogenic upper stage in the single launch configuration. The payload size was a maximum of 4.57 m in diameter and 16.19 meters long
- Payload Adapter—Cone 3926 plus the ACU 2624 lower cylinder and clamp-band
- Launch campaign preparation—the mutual responsibility of NASA, ESA, Northrop Grumman, and ArianeSpace
The first full-color scientific images and spectroscopic data from JWST were released during a televised broadcast from NASA’s Goddard Space Flight Center on July 12, 2022. The five images mark the official beginning of JWST's general science operations. They were selected by an international committee made up of representatives from NASA, ESA, CSA, and the Space Telescope Science Institute. They include the following:
- Carina Nebula (shown below)—a star-forming region called NGC 3324, also called the cosmic cliffs
- Stephan's Quintet—a grouping of five galaxies
- Southern Ring Nebula—planetary nebula
- WASP-96 b—spectra of a hot gas giant planet orbiting a Sun-like star showing the signature of water.
- SMACS 0723—known as Webb's first deep field, an image of a galaxy cluster
One of JWST's first scientific full-color images, showing the Carina Nebula.
The JWST was originally named the "Next Generation Space Telescope," or NGST, as it would build on the work of the Hubble Space Telescope. The telescope would also utilize the next generation technologies, including lightweight deployable mirrors. On September 10, 2002, the project was renamed in honor of James E. Webb (1906- 1992), NASA's second administrator. Webb is best known for leading the Apollo program, which landed the first humans on the moon. He also initiated a space science program, overseeing seventy-five launches during his time as NASA administrator.
In December 2022, scientists confirmed that JWST had observed the most distant galaxies in the universe. Four galaxies were confirmed to have appeared roughly 13.4 billion years ago when the universe was only 350 million years old. This work was part of the JWST Advanced Deep Extragalactic Survey (JADES), analyzing data from the telescope’s Near Infrared Spectrograph to determine how fast galaxies are moving away from the telescope. Their redshift was measured as 13.2, the highest ever observed.
While thousands of exoplanets have been discovered, very few have been imaged directly. Most exoplanets are discovered by measuring dips in the light of the start they are orbiting. In September 2022, JWST captured its first direct image of an exoplanet. Called HIP 65426 b, it was discovered in 2017. To image it, JWST used two of its instruments with several filters and the telescope's coronagraphs (tools that block out the central star). The planet's size (twelve times the size of Jupiter) and orbit (one hundred times the orbital distance of Earth) made it easier to image.
In February 2023, the JWST released details on what appear to be six massive, ancient galaxies that cannot be explained by current theories of cosmology. Existing models show that after a period of rapid expansion, the universe spent hundreds of millions of years cooling down, which allowed gas to coalesce and collapse to form the first stars and galaxies. This period of cooling is known as the dark ages. The discovery of such massive galaxies soon after the big band suggests stars and galaxies began forming much sooner than previously thought.
On October 2, 2023, scientists at ESA released two papers describing free-floating binary objects in the Orion Nebula. The objects have been named Jupiter-Mass Binary Objects or JuMBOs. The existence of these objects challenges existing theories of planetary formation as they are too small to be explained by stellar-like formation conditions (gravitational collapse within gas and dust clouds), but their existence as binary pairs does not suggest they were ejected from star systems. The papers, which are had been peer-reviewed at release, were released at the same time as ESA's image release following the JWST's near-infrared survey of the Trapezium Cluster & inner Orion Nebula.
