The James Webb Space Telescope, also known as JWST, is a space telescope that studies the universe in the infrared. Its great resolution and sensitivity enable it to examine things that the Hubble Orbit Telescope can't see because they're too ancient, far away, or faint. It is the largest optical telescope in space. [8] This will make it possible to conduct research in a wide range of astronomical and cosmological topics, including the observation of the earliest stars, the birth of the first galaxies, and the thorough atmospheric characterisation of possibly habitable exoplanets.
The European Space Agency (ESA) and the Canadian Space Agency were partners with the U.S. National Aeronautics and Space Administration (NASA), which oversaw JWST's design and development (CSA). Telescope development was overseen by the Space Telescope Science Institute in Baltimore and the NASA Goddard Space Flight Center (GSFC) in Maryland.
Features
The James Webb Space Telescope has a mass that is about half of Hubble Space Telescope's mass. The JWST has a 6.5-meter (21 ft)-diameter gold-coated beryllium primary mirror made up of 18 separate hexagonal mirrors. The mirror has a polished area of 26.3 m2 (283 sq ft), of which 0.9 m2 (9.7 sq ft) is obscured by the secondary support struts,[13] giving a total collecting area of 25.4 m2 (273 sq ft). This is over six times larger than the collecting area of Hubble's 2.4-meter (7.9 ft) diameter mirror, which has a collecting area of 4.0 m2 (43 sq ft). The mirror has a gold coating to provide infrared reflectivity and this is covered by a thin layer of glass for durability.
JWST is designed primarily for near-infrared astronomy, but can also see orange and red visible light, as well as the mid-infrared region, depending on the instrument. It can detect objects up to 100 times fainter than Hubble can, and objects much earlier in the history of the universe, back to redshift z≈20 (about 180 million years cosmic time after the Big Bang).For comparison, the earliest stars are thought to have formed between z≈30 and z≈20 (100–180 million years cosmic time), and the first galaxies may have formed around redshift z≈15 (about 270 million years cosmic time). Hubble is unable to see further back than very early reionization[17][18] at about z≈11.1 (galaxy GN-z11, 400 million years cosmic time).
The design emphasizes the near to mid-infrared for several reasons:
high-redshift (very early and distant) objects have their visible emissions shifted into the infrared, and therefore their light can be observed today only via infrared astronomy;
infrared light passes more easily through dust clouds than visible light;
colder objects such as debris disks and planets emit most strongly in the infrared;
these infrared bands are difficult to study from the ground or by existing space telescopes such as Hubble.
Rough plot of Earth's atmospheric absorption (or opacity) to various wavelengths of electromagnetic radiation, including visible light
Ground-based telescopes must look through Earth's atmosphere, which is opaque in many infrared bands (see figure at right). Even where the atmosphere is transparent, many of the target chemical compounds, such as water, carbon dioxide, and methane, also exist in the Earth's atmosphere, vastly complicating analysis. Existing space telescopes such as Hubble cannot study these bands since their mirrors are insufficiently cool (the Hubble mirror is maintained at about 15 °C [288 K; 59 °F]) which means that the telescope itself radiates strongly in the relevant infrared bands.
JWST can also observe objects in the Solar System at an angle of more than 85° from the Sun and having an apparent angular rate of motion less than 0.03 arc seconds per second. This includes Mars, Jupiter, Saturn, Uranus, Neptune, Pluto, their satellites, and comets, asteroids and minor planets at or beyond the orbit of Mars. JWST has the near-IR and mid-IR sensitivity to be able to observe virtually all known Kuiper Belt Objects.In addition, it can observe opportunistic and unplanned targets within 48 hours of a decision to do so, such as supernovae and gamma ray bursts.
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