The next great space observatory is off to a shiny start. The protective covers on the James Webb Space Telescope’s (JWST) primary mirror have finally been lifted.
Billed as the successor to the Hubble space telescope, JWST will afford us fascinating views of the universe when it is launched in October 2018. It has been in construction since almost the start of this century, with its finish date constantly postponed, but now it is closer than ever to being ready.
The scientists and engineers working on JWST at NASA’s Goddard Space Flight Center are now completing the assembly of all the other instruments for the telescope. Over the next two years, the team will carry out tests to make sure JWST is ready to be flown into space.
The primary mirror, which you can see in all its glory below, is composed of 18 hexagonal segments, each the size of a coffee table and weighing about 20 kilograms (46 pounds). The mirrors are made of beryllium, which allows them to be both light and strong, and they are coated with a thin gold film to improve the mirrors’ reflection of infrared radiation.
Assembly of the primary mirror began in November 2015, and the final segment was installed on February 3. The mirror is larger than any rocket, so both the mirror and the heat shield are designed to fold out once JWST reaches its destination 1.5 million kilometers (932,000 miles) from Earth.
Engineers performing tests on JWST at NASA's Goddard Space Flight Center's clean room in Greenbelt, Maryland. NASA/Chris Gunn
JWST will be positioned at the L2, the second Lagrange point. This is a point in space where the gravitational attraction of the Sun and the Earth balance the centrifugal pull a small object might experience. Satellites in L2 remain at the same distance from us and move with the Earth around the Sun.
Although the observatory is considered the replacement of Hubble, it will do much more than its incredible predecessor. JWST will look at the universe in visible light and near-to-mid infrared, allowing it to look further back in the universe than ever before, hopefully spotting the first stars that ever shone.
JWST, a collaborative project between NASA, the European Space Agency, and the Canadian Space Agency, will also investigate our astronomical "backyard," looking at gas and dust clouds, star-forming clusters, and even obtaining direct imaging of some nearby exoplanets.
Main image via NASA/Twitter