Nearby ‘Super-Earth’ Provides Best Chance for Study of Exoplanet Atmospheres

A rocky, volcanic exoplanet with an 800-degrees temperature is putting on a show for a team of international researchers who are trying to figure out if it has an atmosphere.

Moments of the virtual journey, with overlaid astronomical data. (Credit: RenderArea)

(CN) — The first breath taken by a human on another planet will not happen by accident. It will take a lifetime of measurements and study aimed at alien planets hurtling through space. Because before that first breath can happen, we will need to understand what atmosphere is waiting for us. But if there is a suitable homeworld out in the cosmos it could already be calmly beckoning to us from across the way.

We just have to look.

Suitable candidates to study from Earth are few and far between and the conditions have to be just right. Enter Gliese 436, a red dwarf in our galactic backyard at around 33 light years from Earth. Orbiting the red dwarf is the Neptune-sized Gliese 436b, a rocky exoplanet, which is the subject of an international study published in the journal Science.

Don’t start packing for the exoplanet anytime soon as it’s not suitable for human colonization, with a planetary temperature of about 800 degrees and a gravitational pull that is roughly 70% stronger than what’s experienced on Earth.

But the celestial body is prime for studying.

Researchers used powerful spectrograph instruments at the Calar Alto CARMENES program located in Andalusia, Spain. The study is able to use Doppler radial velocity to track exoplanets orbiting stars with incredible precision.

“Imagine, we can measure the velocity of stars with the velocity precision of an average human walking velocity,” said lead researcher Trifon Trifonov from the Max Planck Institute for Astronomy and head of the CARMENES program. “We regularly monitor our targets, and we look for periodic changes in their velocity towards the observatory, which would indicate the presence of planetary companions.”

Gliese 436b is the third-closest exoplanet to Earth and happens to pass between our planet and its red dwarf star. In simpler terms, Gliese 436b passes in front of its star at the point where it receives a sliver of light that is visible to Earth. A second measurement happens when the exoplanet’s hemisphere is illuminated.

The exoplanet happens to be within our galaxy and falls right in line with NASA’s Transiting Exoplanet Survey Satellite spacecraft, which just so happens to search for exoplanets. Literally the stars have aligned to grant researchers a prime view of the exoplanet.

“Combining a well-characterized planetary mass and orbital configuration from Doppler data, and precise planetary radius and orbital period from transits for such a close exoplanet are what make it an exceptional discovery,” said Trifonov.

The exoplanet is about 30% larger than Earth, has a mass of about 2.8 times our planet and is the ideal subject for atmospheric research.

“The discovery of Gliese 486b was a stroke of luck. A hundred degrees hotter and the planet’s entire surface would be lava. Its atmosphere would consist of vaporized rocks,” said study co-author José Caballero of the Centro de Astrobiología. “On the other hand, if Gliese 486b were a hundred degrees colder, it would have been unsuitable for follow-up observations.”

It’s a Goldilocks-scenario and while it’s just right for researchers to study, the exoplanet is rocky and interspersed with glowing lava rivers and volcanoes. So, not the ideal destination for humans.

“However, we still do not know if Gliese 486b has an atmosphere at all. The planet possibly only has a tenuous atmosphere, if any,” Trifonov said in an email. “Our models are consistent with both scenarios because stellar irradiation tends to evaporate atmospheres, whereas, at the same time, the planetary gravity is strong enough to retain it. Figuring out the balance of those contributions is very difficult, and only direct observations may reveal the answer.”

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