(CNN)In 2016, astronomers found a potentially habitable planet called Proxima b around the star Proxima Centauri, which is only 4.2 light-years from Earth. Now, researchers have traced a second signal they believe belongs to a super-Earth orbiting the same star, increasing the intrigue of this neighboring planetary system and its potential.
Proxima Centauri is the closest star to our sun. It’s a low-mass red dwarf star known as an M-class dwarf. The star is in a triple star system known as Alpha Centauri, including binary pair Alpha Centauri AB.All of these stars are within the faint Centaurus constellation, which can’t be seen with the unaided eye.After the discovery of the first planet around Proxima Centauri, researchers speculated about the existence of another planet in the system.
Astronomers used the Atacama Large Millimeter/submillimeter Array of telescopes in Chile to trace light signals that appeared to be coming from that direction.The authors of a new study, published Wednesday in the journal Science Advances, were able to look at more than 17 years of radial velocity data from the well-studied star system and determine if the signal belonged to an orbiting planet.The radial velocity method is based on gravity and the Doppler effect, in which light increases or decreases in frequency as a source and observed objects move toward or away from each other.
Meet the planet neighbours
The newly discovered second planet, Proxima c, is likely a super-Earth with a mass larger than Earth’s but smaller than Uranus and Neptune. The researchers estimate that it 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.
Proxima b is 1.3 times the size of Earth and orbits its star every 11.2 days. It is in a close orbit of Proxima Centauri: only 5% of the distance between the Earth and the sun. They are even closer together than Mercury and the sun. But because its star is much cooler and fainter than our sun, Proxima b has a temperature that is suitable for liquid water to exist on the surface without evaporating.Given the proximity to its star, Proxima b is also subject to less pleasant factors like ultraviolet and X-ray flares that are 100 times the intensity of what Earth receives from the sun. If there is life on the planet, it would be affected by this radiation, but it is pure speculation as to what kind of effect.
Even though Proxima b is within the habitable zone of its star, meaning liquid water could exist on the surface, that doesn’t mean it’s actually habitable. And the radiation it likely faces has likely stripped away key elements for life like hydrogen, oxygen and nitrogen.The newly discovered planet is intriguing because further study could reveal how low-mass planets form around low-mass stars, the researchers said. And this particular planet flips the typical theory of super-Earth planet formation on its head.It’s beyond the “snowline” of the system, which suggests any water on the planet would be frozen. Super-Earths typically form near the snowline, but not beyond it.