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Des chercheurs ont exploité la sensibilité aux rayons ultraviolets du télescope spatial Hubble pour observer une exoplanète géante en formation. Sur cette vue d’artiste, le gaz extrêmement chaud qui tombe sur la planète, transporté par des lignes de champ magnétique de son disque circumplanétaire vers son atmosphère. © Nasa, ESA, STScI, Joseph Olmsted (STScI)

Hubble witnesses the birth of a giant planet

Thousands of exoplanets have been identified by astronomers since October 1995 and the shocking announcement of the discovery of their first, 51 Pegasi b. But researchers are still unaware of the details of the giant planet’s growth process. New images provided by the Hubble Space Telescope could be a game-changer.

“We don’t know much about Nomou Giant planets»Brendan Bowler, a researcher at the University of Texas at Austin (USA), admits to A. NASA press release. “This planetary system gives us the first opportunity to see material that falls on a planet.” This system that the astronomer talks about is that which Hubble Spatial Telescope. A system with a planet the size Jupiter Still in training. feed on Thing Who surrounds his host, young star.

I mention it among the most of 4,000 exoplanets have been discovered So far by researchers, only about fifteen have been filmed live. They usually appear as simple light points. However, more than 30 years after its launch, the Researchers A new way to use Hubble to get first-hand images of planets outside our solar system.

The Astronomy scientists The PDS 70, a Dwarf star Orange is located around 370 Light years in Earth. Because it is known that it hides two of the constituent exoplanets in a huge disk of dust and Gas Who surrounds it. PDS 70 b, which Hubble observed, is only five million years old. It is still in the process of accumulating matter.

An exoplanet is growing less rapidly today

Thanks to the notes in the field ultraviolet For the fine cleaning of the light emitted from the PDS 70, the Hubble Spatial Telescope Researchers were shown unique images of the radiation of hot gases falling on the giant planet. What even to appreciate Speed Who grows the latter. Astronomers claim that an exoplanet has already accumulated five times Mass Jupiter. But his rateAccumulation Dropped. If it stayed where it is today for another million years, it would only grow to about a hundredth of the mass of Jupiter.

Although the data indicates that the giant planet is at the end of its formation process, there are still immediate measurements. Researchers will need more to see how the rate of accumulation is currently changing over time.

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According to astronomers, the exoplanet PDS 70 b is surrounded by a disk around the planet that pulls the much larger disk surrounding its host star. Lines magnetic field That extends from its gas and dust disc to Ambiance Transfer of matter to the surface of the planet. The trigger points that researchers seem to notice on Hubble images are particularly bright.

Alma expels the giant planets in the formation

Thanks to the Alma Observatory in Chile, astronomers have found, within the disks of gas and dust surrounding four young stars, indisputable evidence of the recent formation of planets with a mass several times the mass of Jupiter. Also, measurements made on the surrounding gas made it possible to better define its properties.

An article fromWhich – which Published on 06/2016

Several planets are attracted around each or nearly every star. However, the conditions for their training are still partly misunderstood today. In order to lift this veil from obscurity, astronomers study Gas and dust discs Revolves around the young stars where Planets are forming. So the strengthAlmaThe large (sub) millimeter network in Atacama, Chile, enabled them to overcome the smallness of these disks as well as their distance from Earth.

Transient disks are a special type characterized by the absence of dust in their center where the host star is located. This void will result from one of the following scenarios: Either strong Slots The stellar and condensed radiation washed away or destroyed this material (a process called light evaporation), meaning that this matter had been expelled by Huge young planets are in the formation While they were gravitating around their star.

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Unmatched sensitivityAlma The sharpness of the recently obtained images enabled a team led by Nienke van der Marel of the Leiden Observatory in the Netherlands, with an unprecedented degree of accuracy, to map the distribution of gas and dust in the four transient disks for a value of SAR 21, HD 135344B (or SAO 206462) and DoAr 44 and Oph IRS 48. Results obtained and published in Astronomy and Astrophysics, It enabled them to focus in one of the two ways.

Dust holes and gas cavities

The newly obtained images show the presence of large amounts of gas (mainlyhydrogen) Inside the dust holes. To the researchers’ amazement, it emerged that the gas also has a central cavity, up to three times smaller than the dust gap.

For them, this observation finds one unique explanation: the newly formed massive planets cleaned the gas as they described. Eye socket About the central star and the dust particles trapped at the periphery (see also this topic) According to Pierre Barge, Oph-IRS 48 and the Planetary Generation Vortex »).

Thanks to Alma, astronomers have discovered remarkable differences between the gas cavities and the dust holes in the disks surrounding the four young stars. These new observations constitute undeniable evidence of the recent formation of planets with many Jovian blocks within these disks. © Alma, Eso, NAOJ, NRAO, M. Kornmesser

Previous observations had already indicated the presence of gas inside the dust ventsNienke van der Marel. Alma was able to map the material to the entire disk using a file Precision Much higher than any other tool, we were able to exclude the other scenario considered so far. Clearly, such a deep cavity favors planets with masses several times the mass of Jupiter and results from their scanning of the disk. “

It is interesting to note that these observations were made while the antenna assembly was present Construction On the Chagnantur Plateau in Chile. He’s only been awarded 10% of his current opponent power.

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Universal mechanism?

New studies, applied to other transient disks, may help demonstrate the universality of this planetary clearing scenario. By then, Alma’s observations will have provided astronomers with invaluable insight into the complex process of Planetary formation.

“All transient disks studied to date that have large dust holes also feature gas cavities. Thanks to ALMA, we can now determine where and when these are formed. Giant planets Inside these disks, and then compare the obtained results with models of planet formationSays Ewen van Dieschuk of Leiden University in the Netherlands and the Max Institute Planck Dedicated to physique Alien, in Garching, Germany. Direct detection of planets is within reach of current instruments and next-generation telescopes currently under construction, such asE-ELTThe European Giant Telescope will allow us to push these limits back. Alma allows you to target future notes. “

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