Compact System of Super-Earths Found around Lacaille 9352 | Astronomy

Pablo Tucker
June 27, 2020

They were able to infer the planets around the star by using a technique called "Doppler wobble", which lets them watch for the tiny movements of the star that are caused by the gravitational pull of the planets around them. They combined data from HARPS with measurements of the star-spanning for about 20 years.

The planets, named Lacaille 9352b (Gliese 887b) and Lacaille 9352c (Gliese 887c), have minimum masses of 4.2 and 7.6 Earth masses, respectively.

The researchers also detected an unconfirmed signal, raising hopes of a third planet with a more "temperate" orbit.

The radial velocity method to detect exoplanet
The radial velocity method to detect exoplanet

The research, which was published in Science, holds a lot of promise, but we don't yet possess the technology to view these Earth-alikes in greater detail. Possibly the most exciting thing about these two new super-Earths is they lie close to the red dwarf's habitable zone, where water can exist in liquid form, and could be rocky worlds just like Earth and Mars. It is also claimed to be much dimmer than the Sun, and about half its size. This indicates that the two super-Earths are moving rapidly, much faster, even than Mercury.

Both receive between 2.5 and eight times more energy from their star than Earth receives from the sun.

A possible third world may orbit the star every 50 days and could be in its "habitable zone", the orbit around a star where a planet could support liquid water, potentially upping the odds for life.

In observing and studying the star, the researchers discovered some good news. Still, "we've been looking for exoplanets orbiting Gliese 887 for almost 20 years, and while we saw hints of a planetary signal, it wasn't strong enough to convince ourselves that it was a planet", study lead author Sandra Jeffers, an astrophysicist at the University of Göttingen in Germany, told "By a quiet star, I mean that it doesn't have the dark starspots or the energetic outbursts [flares] that we see on the Sun".

If the star was as active as our Sun, it is likely that a strong stellar wind - outflowing material which can erode a planet's atmosphere - would simply sweep away the planets' atmospheres.

These findings only further prove what astronomers had already suspected in that red dwarf stars could host more than one planet. Davies was not involved with the study. Scientists say that these new planets can have thicker atmospheres than Earth, and potentially contain life. The telescope, expected to launch next year, can peer through the atmospheres of exoplanets and help characterize their compositions.

"We've really started valuing these bright systems so that we can do all of this much more detailed analysis of the atmospheres of these planets", exoplanet researcher Jessie Christiansen, who wasn't affiliated with the study, told Axios.

Previously, the Red Dots team found other exoplanets close to our sun, like the planets orbiting Proxima Centauri and Barnard's star.

"This is why we are now unable to say that the third signal is actually a planet". It's believed that these newfound planets are indeed in or at least near the habitable zone, making them very interesting to anyone who is searching for life outside of Earth.

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