Free Astronomy Magazine May-June 2018

35 MAY-JUNE 2018 SPACE CHRONICLES A RIEL will be placed in orbit around the Lagrange Point 2 (L2), a gravitational balance point 1.5 million kilometres beyond the Earth’s orbit around the Sun. [ESA/STFC RAL Space/UCL/Europlanet-Science Office] through the atmosphere, thus mak- ing them remotely observable. ARIEL will have a telescope with a one-metre diameter primary mirror to collect visible and infrared light from these planetary systems orbit- ing distant stars. A spectrometer will split the light into its constituent ‘rainbow’ in order to trace the chemical fingerprints of the atmos- pheric molecules when the planet passes in front of, or behind, the star. A photometer and scanning sys- tem will gather information on the presence of clouds in the exoplanet atmospheres and allow the tele- scope to be pointed towards the star with great stability and precision. The ARIEL satellite will be launched from Kourou in French Guiana and will be placed in orbit at the L2 La- grange point, which is a point of gravitational equilibrium 1.5 mil- lion kilometres from the Earth (the Sun, Earth, and L2 point form a straight line). At this point the satellite will be pro- tected from the Sun and will have an unimpeded view of the whole sky in order to observe a large num- ber of exoplanets. The James Webb Space Telescope (JWST), scheduled for launch in 2019, will also be lo- cated in this region. In theory, there will be no overlap in time, since ARIEL is planned as a successor mis- sion to the JWST in the study of ex- oplanets and their atmospheres. The project manager of Spain’s par- ticipation in the project, Josep Colomé of the IEEC-CSIC, empha- sizes: “ESA’s selection of ARIEL is great news. It gives recognition of the engineering work carried out over the last two years and will boost the space technology we’re developing for this and other mis- sions in close collaboration with In- dustry in the sector. ARIEL enables us to work with world-leading re- search centres and puts us in the first division of space technology” . ! cally large enough to give us a truly representative picture of what these planets are made of. This will enable us to answer questions on how the chemistry of a planet is linked with the environment in which it was formed, and how its birth and evo- lution depend on the star it orbits” . This mission will study a diverse pop- ulation of exoplanets, ranging from those of the size of Jupiter and Nep- tune to the so-called super-earths, in a large variety of environments. The main emphasis of the mission will be on planets in close orbits around their stars. Hot exoplanets, with temperatures of up to 2000°C, are a natural laboratory in which to study the chemistry and formation of planets, given that their high temperatures maintain the different molecular species in circulation