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Too much UV light could turn gas planet into sad rock cores

Artistic representation of WASP-69b and its ghostly tail.
Image: Gabriel Perez Diaz, SMM

The atmosphere of a gas giant exoplanet 163 light-years from Earth is blown up into space by its host star, forming a ghostly tail, responsible for excessive ultraviolet radiation The Celestial Phenomenon According to a new study, it is a discovery that could provide new insights into planet formation.

The superbly named WASP-69b is about the size of Jupiter, but unlike Jupiter, it is barely 4 million kilometers away from host star. A year on WASP-69b lasts only 3.6 days and astronomers from the Canary Islands Institute of Astrofísica de Canarias (IAC) describe how ultraviolet radiation from the star ejects helium particles in a new article published today in Science. 69b with such power that the tremendous gravity of the planet can not hold it the escaping gases formed a pronounced comet-like tail, which the researchers could prove.

Helium can b It is the second most abundant element in the Universe, but it is known to be difficult to detect near distant exoplanets. To find out, a team of astronomers, led by Lisa Nortmann of the IAC, used the CARMENES instrument attached to the 3.5-meter telescope of the Calar Alto Observatory in Spain. This tool detects wavelengths in the visible and near infrared ranges at high resolutions so that astronomers can recognize certain chemical signatures such as helium and the speed with which they move.

With CARMENES, astronomers WASP-69b, as we saw it passing Earth's star, observed an astronomical technique known as the transit method.

"We observed a stronger and longer-lasting darkening of starlight in an area of ​​the spectrum where helium gas absorbs light," Nortmann said in a statement. "The longer duration of this absorption allows us to deduce the presence of a tail."

Using the same technique, astronomers observed several other exoplanets in similar predicates. However, none of the observed exoplanets showed the same helium outgassing effect except one – a hot Jupiter known as HD 189733b. But instead of a tail, this planet was surrounded by a helium balloon that ran in different directions into space.

Artist's impression of HAT-P-11b, which is so swollen that it resembles an inflated balloon.
Image: Denis Bajram

In a related paper, also published today in Science, astronomers describe the exoplanet HAT-P-11b, which, like WASP-69b and HD 189733b, also loses its helium.

So this is apparently something that happens to a select group of exoplanets. Why some of the closely spaced gas giants bleed their helium while others were unknown, the team turned to another tool: the European Space Agency's multi-mirror X-ray mission (ESA XMM-Newton). , As this telescope showed, the smoking pistol turned out to be extreme ultraviolet radiation from the planet's host stars.

In terms of the mechanism of action, the researchers theorize that the helium particles are over-energized by abundant amounts of incident ultraviolet radiation, causing the particles to be ejected from the atmosphere into space. But that's just the theory, more observations, especially with the instrument CARMENES, could provide information about this mysterious process.

That's all really cool, but this discovery could also point to the processes of planet formation. Finally, the researchers speculate that the gas giants could be completely deprived of their atmosphere. All that remains is a compact rocky core with densities and perhaps even masses, similar to Earth or Venus. It may represent a new and seemingly intricate way for the emergence of rocky planets, but it is still only a theory.

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Read more 19659018] Considering this possibility, astronomers should now look for rocky planets with extremely short orbital periods, which could be the remnants of this process. Better yet, they could detect gas giants in the final stages of helium outgassing, as this could be considered more convincing (ie, at cosmological distances, it might be difficult to distinguish rocky remnants of vaporized gas giants from accumulated rocky planets).

Fortunately, the next generation of telescopes, including the Transiting Exoplanet Survey Satellite (TESS) and the yet-to-launch James Webb Space Telescope (JWST), may be strong enough to get the job done.


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