The James Webb Space Telescope – why do we need it?
The James Webb Space Telescope (JWST) is the successor to the Hubble Space Telescope and is due to be launched on an Ariane 5 rocket in Spring 2019. The JWST will be the premier space observatory of the next decade, supporting thousands of astronomers worldwide.
The telescope will study every phase in the history of our Universe, ranging from the first luminous glows after the Big Bang, to the formation of solar systems capable of supporting life on planets like Earth, to the evolution of our own Solar System.
JWST is a large infrared telescope with a huge primary mirror that has a diameter of 6.5 meters (see image below). The sunshade, which is the largest structure of JWST – the size of a tennis court, will act as a shield to the deployed primary mirror.
The Successor to Hubble
JWST is designed not as a replacement, but as a successor that will expand on the scientific success of the Hubble Space Telescope. JWST is designed to operate at very low temperatures (around -230° C) and will primarily look at the Universe in the infrared, looking deeper into space to see the earliest stars and galaxies that formed in the Universe and to look deep into nearby dust clouds to study the formation of stars and planets. It is planned that the mission will last around 10 years, where the mission lifetime will depend on the amount of fuel that is used for maintaining the orbit of the spacecraft and instruments.
Thirty minutes after launch JWST will deploy from the Ariane 5 Rocket and will immediately deploy the solar array. In the following days and weeks after launch there will be several trajectory correction manoeuvres followed by the commencement of the major deployment, firstly the sunshield pallets and then the telescope.
During the first couple of months of the mission the four instruments will be turned on with the final instrument MIRI becoming operational. At the end of the third month the first science-quality images will be taken and JWST will complete its initial orbit around L2 (see image below), its home for the next decade.
(The five Lagrangian points for the Sun-Earth system are shown here. An object placed at any one of these 5 points will stay in place relative to the other two. The L2 point, where the JWST will be is 1.5 million km from Earth. Credit: NASA)
JWST has four mission science goals:
1) To search for the first galaxies and stars that formed after the Big Bang, and to learn how they evolved throughout the history of the universe.
2) Determine how galaxies evolved from their formation until the present day looking inside stellar nurseries and at planets forming in dusty disks around young stars.
3) Observe the formation of stars from the first stages to the formation of planetary systems.
4) Measure the physical and chemical properties of planetary systems and investigate the potential for life in those systems.
The Mid-Infrared Instrument (MIRI) was developed in a collaborative effort between scientists and engineers from ten European countries, led by the UK and the Jet Propulsion Laboratory (JPL), with the support of ESA and NASA. The UK team is made up of a partnership between the Science and Technology Facilities Council (STFC), University of Leicester and Airbus Defence and Space with funding from the UK Space Agency.
In addition to MIRI, University College London’s Mullard Space Science Laboratory is contributing NIRSpec’s on board calibration system and ground support equipment.
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