Using an adaptive optics system and coronagraphic facility at ESOs Very Large Telescope, an international team of astronomers has discovered and directly imaged a warm super-Jupiter exoplanet around the young star HIP 65426.

An artists rendering of a super-Jupiter exoplanet. Image credit: NASAs Goddard Space Flight Center / S. Wiessinger.

The new world, dubbed HIP 65426b, is about 6 to 12 times more massive than Jupiter and has a radius of approximately 1.5 Jupiter radii.

As a giant planet larger than Jupiter, its classified as a super-Jupiter.

HIP 65426b orbits the A2-type star HIP 65426, which is almost 3,000 degrees Kelvin hotter and twice as massive as the Sun.

Also known as HD 116434, the star lies 363 light-years away in the constellation Centaurus.

The massive planet orbits HIP 65426 in about 600 years and is 92 AU (astronomical units) from the star, which is three times further than Neptunes distance from the Sun.

It has an estimated temperature of 1,300-1,600 degrees Kelvin and is much hotter than Jupiter.

Given its physical and spectral properties, HIP 65426b occupies a rather unique placement in terms of age, mass and spectral-type among the currently known imaged planets, the astronomers said.

It represents a particularly interesting case to study the presence of clouds as a function of particle size, composition, and location in the atmosphere, to search for signatures of non-equilibrium chemistry, and finally to test the theory of planet formation and evolution.

HIP 65426b was discovered with the Spectro-Polarimetric High-Contrast Exoplanet Research (SPHERE) instrument at ESOs Very Large Telescope in Chile, which took the direct image of the planet.

Direct images of exoplanets are still very rare, but they contain a wealth of information about planets such as HIP 65426b, said team member Dr. Thomas Henning, of the Max Planck Institute for Astronomy in Germany.

The analysis of the direct light of the planet allows us to constrain the composition of the planets atmosphere with great confidence.

The SPHERE observations indicate the presence of water vapor and reddish clouds, similar to Jupiters.

The photo of the super-Jupiter HIP 65426b (lower left). Image credit: ESO / SPHERE Consortium / G. Chauvin et al.

Dr. Henning and colleagues estimate the planetary system is only 14 million years old.

We would expect a planetary system this young to still have a disk of dust, which could show up in observations, said team member Dr. Gael Chauvin, from the Universities of Grenoble and Chile.

HIP 65426 does not have such a disk known for the moment a first indication that this system doesnt quite fit our classical models of planetary formation.

Using ESOs HARPS instrument, we realized that HIP 65426 was a young star and was turning very fast on itself, about 150 times faster than the Sun two elements that raise the question of the formation of the planet, the scientists said.

The team is offering two scenarios to explain the formation of HIP 65426b.

Initially, HIP 65426b would have formed much closer to the star, and at least one other massive body would have formed as well. At some point, HIP 65426b and that other body would have come close enough for HIP 65426b to be catapulted outwards (up to its current great distance) and the other body moving inwards and merging with the star (causing the stars rapid rotation). The planets traversing the system could also have destabilized the disk, explaining why it did not survive long enough to be observed, they said.

An alternative explanation would involve particular dynamics of the protoplanetary disk, with both the star and the planet forming by collapse at the same time by fragmentation which would still require an explanation for why the disk was so short-lived to have vanished by now.

A research paper reporting this discovery will be published in the journal Astronomy & Astrophysics. The paper is also publicly available at arXiv.org.

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G. Chauvin et al. 2017. Discovery of a warm, dusty giant planet around HIP 65426. A&A, in press; arXiv: 1707.01413

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Astronomers Directly Image Super-Jupiter around HIP 65426 - Sci-News.com