2023-12-01 07:00:02
ESO’s Very Large Telescope (VLT) under observation. In this photo, taken from the VLT platform looking north-northwest at dusk, the four 8.2-meter Unit Telescopes (UTs) are visible. From left to right, Antu, Kueyen, Melipal and Yepun, the Mapuche names of the giant VLT telescopes. SERGE BRUNIER/ESO
In the Residencia, the long building which accommodates, at an altitude of more than 2,400 meters, in the heart of the Atacama Desert (Chile), people who come to work at the Very Large Telescope (VLT), Arthur Wigan, in mid-November, is preparing for a few sleepless nights. A specialist in instrumentation but also in the detection and characterization of exoplanets, this researcher from the Marseille Astrophysics Laboratory is preparing to carry out the very first observations of a new instrument, Hirise, which has been installed on one of the four 8.2 meter telescopes of the VLT.
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In reality, Hirise is a matchmaker: thanks to this device, the two main instruments of this telescope, called “Sphere” and “Cires+”, have just been coupled. Everyone has great qualities, but also a weakness. The first fact of direct imaging of exoplanets: unlike the two main methods of detecting extrasolar planets, which only measure the properties of their targets without ever seeing them, Sphere is capable of obscuring the blinding light of the stars in order to photograph the planets that accompany them. “But, with this instrument, we are quite limited in terms of the details that we can obtain in the light spectrum of exoplanets, adds Arthur Vigan. Conversely, on the other side of the telescope, we have the Crires+ instrument, a very high resolution spectrograph, but which is not designed to see faintly luminous objects. near stars. »
Bricolage
The idea behind Hirise is to add the strengths of each instrument to overcome their respective limitations. To do this, we had to tinker a little, connect the two machines by 80 meters of optical fiber and slide Hirise into the small space remaining along Sphere. The cost of the operation, 1.5 million euros, mainly covered by a grant from the European Research Council, is quite modest. “Clearly, Hirise is a research and development project, explains Arthur Vigan. This is a fairly economical concept, which leverages existing instruments. »
The first scientific campaign, in November, only includes three nights of observation, but many others will follow, since the agreement with the European Southern Observatory (ESO), which manages the VLT, runs for three years. The researchers’ objective is to target, around nearby stars, young giant planets, which still emit, in the infrared, the energy stored during their formation. “Beyond a few hundred million years, planets radiate less and become more difficult to detect,” recognizes Arthur Vigan. Thus, despite its imposing size, Jupiter, 4.5 billion years old, would be impossible to spot for an extraterrestrial astronomer located around thirty light years from Earth.
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