Discovered a planet that changes its atmosphere with each stellar orbit

A young planet, located about 32 light-years from Earth, has exhibited dynamic changes in its atmosphere during each revolution around its parent star . The Hubble Space Telescope made this fascinating discovery while observing the planet orbiting AU Microscopii (AU Mic), an extraordinarily active red dwarf star. The news was published by “ The astronomical journal ”

During one of Hubble's initial observations, it was noted that the planet seemed to be constantly maintaining its atmosphere. However, there was a twist in this discovery. About a year and a half later, subsequent Hubble observations brought up "clear indications of atmospheric leaks."

The observations indicated that the host star's fierce stellar winds were stripping the planet's atmosphere of hydrogen. Thus the atmosphere of this planet is modified with each orbit around its star and this in an unpredictable way and not previously observed.

This stark variability in atmospheric loss between orbits puzzled scientists because it appeared sudden and unpredictable:

“We have never seen atmospheric runaway go from completely undetectable to very detectable in such a short period as a planet passes in front of its star. We were really expecting something very predictable, repeatable. But it turned out to be strange. When I first saw it, I was like, 'This can't be right,' " said Keighley Rockcliffe of Dartmouth College in Hanover, New Hampshire, in an official statement.

Possible reasons for atmospheric variability

In 2020, the Spitzer Space Telescopes and NASA's Transiting Exoplanet Survey Satellite (TESS) discovered the planet, AU Mic b. which revolves around AU Microscopii. This is a young star, less than 100 million years old. For comparison, the Sun is about 4.6 billion years old.

In this young system, the planet has an orbital period of 8.46 days, located nine million km from the star.

Hubble observed variations in the star's brightness corresponding to the “leakage” of hydrogen from the planet's atmosphere. Due to the planet's proximity to the host star, the atmosphere was subjected to high radiation and heat, thus forcing the hydrogen to escape outwards.

The fiery eruption of highly charged flares from the star could be the cause of the hitherto unseen weathering.

A possible explanation for the lack of hydrogen during one of the planet's transits is that a powerful stellar flare, seen seven hours earlier, may have photoionized the escaping hydrogen to the point where it became transparent to light, and thus was undetectable. ", has explained. the release.

The authors have advanced another possible explanation for this strange behavior, suggesting that extreme stellar wind may be shaping planetary outflow. As a result, the atmosphere is sometimes observable and sometimes not from Hubble.

The extreme nature of red dwarf stars

Red dwarf stars, such as AU Microscopii, make up the majority of stars in our home galaxy. These stars are significantly cooler and less massive than the Sun.

Space scientists have long speculated whether such stars could pave the way for potentially habitable worlds to form in their system. However, young red dwarfs are extremely eruptive, often bombarding any planet orbiting close to the star.

There are some exceptionally high period events in which the star releases tremendously powerful energy that can persist considerably longer than that of other stars such as the Sun.

This harsh stellar environment would make it impossible for any nearby planet's atmosphere to flourish, especially within the first 100 million years of star formation. That's why the planet could end up without an atmosphere forever.

For these reasons, it has been difficult to draw definitive conclusions about the search for habitable worlds around red dwarf stars.

“ We want to find out what types of planets can survive these environments. What will they ultimately look like when the star settles down? And will there eventually be any chance of habitability, or will they end up just being burnt planets?” said Rockcliffe. “Eventually they lose most of their atmospheres and their surviving cores become super-Earths? (i.e. rocky planets much larger than Earth) We don't really know what those final compositions look like because we have nothing like them in our solar system ,” he concluded.

---

---

The article Discovered a planet that changes its atmosphere with each stellar orbit comes from Scenari Economics .

---

This is a machine translation of a post published on Scenari Economici at the URL https://scenarieconomici.it/scoperto-un-pianeta-che-cambia-atmosera-ad-ogni-orbita-stellare/ on Sat, 29 Jul 2023 12:00:09 +0000.