Astronomers have traced a signal they believe belongs to a super-Earth orbiting Proxima Centauri. But more observations are needed to confirm it.
In 2016, astronomers discovered a potentially habitable Earth-size planet called Proxima b orbiting the red dwarf Proxima Centauri. The star is in a triple star system (Alpha Centauri), including binary pair Alpha Centauri AB.
The Proxima Centauri system lies just 4.2 light-years away from us and is the closest star to our sun.
Now, astronomers have found another candidate exoplanet orbiting our neighbor star. The researchers published a paper announcing these results in the journal Science Advances.
Proxima b lies in the habitable zone of its star, meaning liquid water could exist. But the exoplanet is tidally locked to its host star, meaning it has a hot dayside and a cold nightside. Because red dwarfs are very active stars, powerful flares may have stripped the planet’s atmosphere long ago.
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However, the discovery of a second planet, even though it’s likely too far away from its star for liquid water, is intensifying interest in the Proxima Centauri system. But scientists need follow-up observations to confirm it as a planet.
The newly discovered second planet, Proxima c, is likely a super-Earth with a mass about half that of Neptune. The object completes an orbit of Proxima Centauri every 5.2 Earth years.
The first planet found around the star, Proxima b, is six times smaller and is 30 times closer to its star, which also makes it warmer, the researchers said.
Also, Proxima C orbits far from the “habitable zone”, therefore it is a frigid world with a temperature of about -200 C if it has no atmosphere.
But worlds that don’t lie in the traditional “habitable zone” may still be able to harbor life as we know it. For example, Jupiter’s Europa and Saturn’s Enceladus are icy balls, but both possess huge subsurface oceans of liquid water.
However, Proxima c remains a candidate for now and confirming its existence will require additional information. The European Space Agency’s Gaia mission, which is creating a 3D mission of our galaxy, could help refine the signal of the second planet and provide more answers in the future.
“According to our study, if Gaia will deliver the data with the expected quality, and in the absence of any unknown impediment, the detection can be reliably confirmed or dismissed,” Mario Damasso, the lead author of the study said.