The incredible image of an exoplanet forming around a star

The SPHERE instrument equips one of the four telescopes of the Very Large Telescope of the European Southern Observatory (VLT) in Chile. This tool was designed to find exoplanets around stars near the Sun. Commissioned in 2014, SPHERE uses extreme adaptive optics: it has a mirror that corrects the effects of atmospheric turbulence more than 1,200 times per second and at a nanometric scale. It is also equipped with a coronograph that masks the light of the observed star and thus reveals its close environment usually masked by its brightness. This observation technique allowed after some tests to make images of a first exoplanet and in early July 2018, a team of astronomers including several CNRS members announced having managed to obtain the confirmed image of an exoplanet in training. An unprecedented feat

Disturbed Atmosphere

This planet, not yet completely formed, revolves around its star PDS 70 at three billion kilometers away. Almost the one that separates Uranus and the Sun. This star bud is clearly visible in this image obtained by SPHERE: a luminous point, to the right of the center of the image, where the star is masked by the coronagraph. Analysis of the data indicates that PDS 70b is a giant gas planet with a mbad of several Jupiter. The surface of the planet has a temperature of about 1000 ° C and the study of its spectrum reveals the presence of a turbid atmosphere encircling it.

Zoom on PDS 70b. Credit : ESO, N. Risinger (skysurvey.org), DSS. Music: Astral electronic

The SPHERE data also made it possible to study in detail the protoplanetary disk that surrounds PDS 70. It is a temporary structure composed of gas and dust from which the planets are formed. The PDS 70 disk has a very special structure with a giant hole inside. For a long time, astronomers suspected that such holes are caused by the interaction between the disk and a planet in formation. They just have the proof. These results will help refine the search for new exoplanets and better understand the process of their formation.