Astronomy: SPHERE instrument unveils its first exoplanet
The 'planet-finder instrument' of the European Southern Observatory (ESO), which has partially developed and built at ETH Zurich, has discovered its first exoplanet. HIP 65426b is some 385 light-years from us — and it turns out that it is a particularly interesting exoplanet.
The search for exoplanets — other planets orbiting other stars — is one of the most challenging and exciting areas of astronomy today. The exoplanet HIP 65426b has recently been discovered using the external pageSPHERE (Spectro-Polarimetric High-contrast Exoplanet REsearch instrument) instrument on ESO’s external pageVery Large Telescope (VLT). The Institute for Astronomy of ETH Zurich has had an important role in development and construction of the SPHERE instrument: with the project, the team around Prof. Hans-Martin Schmid has been responsible for the construction of the imaging polarimeter, ZIMPOL, which searches for the reflected light from extra-solar planets.
The exoplanet now discovered is warm (between 1000 and 1400 degrees Celsius), and is between six and twelve times the mass of Jupiter. It seems to have a very dusty atmosphere filled with thick cloud, and it orbits a hot, young star that rotates surprisingly fast. Unusually, given its age, the star does not appear to be surrounded by a disc of debris, and the absence of a disc raises puzzling questions about how the planet formed in the first place. The planet may have been formed in a disc of gas and dust and when the disc rapidly dissipated, it interacted with other planets to move to a more distant orbit, where we see it now. Alternatively, the star and the planet may have formed together as a binary system in which the more massive component prevented the other would-be star from accumulating sufficient matter to actually become a star. The discovery of HIP 65426b gives astronomers the opportunity to study the composition and location of clouds in its atmosphere, and to test theories of the formation, evolution, and physics of exoplanets.
SPHERE is a powerful planet finder installed on Unit Telescope 3 of the VLT. Its science goal is to detect and study new giant exoplanets around nearby stars using the so-called direct imaging method. This method aims to directly capture images of exoplanets and debris discs around stars, rather like taking a photograph. Direct imaging is difficult because the light of a star is so powerful that the feeble light reflected by orbiting planets is overwhelmed by the starlight. But SPHERE is designed to bypass this obstacle and to look specifically for the polarised light reflected off a planet’s surface.
The image of HIP 65426b was captured as part of a survey programme called SHINE (SpHere INfrared survey for Exoplanets). SHINE aims to image 600 young nearby stars in the near-infrared using SPHERE’s high contrast and high angular resolution to discover and characterise new planetary systems and explore how they formed.
(Text adapted from the external pageESO press release.)