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 tracked down a second signal that they believe belongs to a super-earth orbiting the same star, which increases the intrigue of this neighboring planetary system and its potential.
Proxima Centauri is the star closest to our sun. It exists together with a double star in Alpha Centauri. Proxima Centauri is a low-mass red dwarf star known as the M-class dwarf. It is located near the bright binary star Alpha Centauri AB (which outshines its cool step-brother, so to speak).
All of these stars are in the faint Centaurus constellation, which cannot be seen with the naked eye.
After discovering the first planet around Proxima Centauri, the researchers speculated about the existence of another planet in the system. Astronomers used the Atacama Large Millimeter / Submillimeter Array of telescopes in Chile to track light signals that seemed to be coming from this direction.
The authors of a new study published in Science Advances on Wednesday were able to view radial velocity data from the well-studied star system for more than 17 years and determine whether the signal belongs to a orbiting planet.
The radial velocity method is based on gravity and the Doppler effect, in which the frequency of light increases or decreases as the source and the observed objects move towards or away from each other.
Stars do not remain completely still when they are orbited by planets. They move in small circles in response to the attraction of the planets. These movements change the light wavelength of the star and move between red and blue depending on the position of the planet. Tracking the layers can help astronomers find planets.
The researchers can’t rule out that the signal is due to the activity of the star’s magnetic field, but the signal they tracked occurred over a period of 1900 days – a strong indicator that a planet was present.
“Even the planetary system closest to us could bring interesting surprises,” said Fabio Del Sordo in an email, study author and postdoctoral fellow at the Physics Department of the University of Crete. “Proxima Centauri is home to a planetary system that is much more complex than we knew, and we don’t know how many unknown features are waiting to be discovered.”
Meet the planet’s neighbors
The newly discovered second planet, Proxima c, is probably a super-earth with a mass larger than that of the earth, but smaller than Uranus and Neptune. The researchers estimate that it orbits Proxima Centauri every 5.2 Earth years.
The first planet found around the star, Proxima b, is six times smaller and 30 times closer to its star, which also makes it warmer, the researchers said.
Proxima b is 1.3 times the size of the Earth and orbits its star every 11.2 days. It is in a narrow orbit from 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 be present on the surface without evaporating.
Due to its proximity to its star, Proxima b is also exposed to less pleasant factors such as UV and X-rays, which are 100 times as strong as the intensity that the Earth receives from the sun. If there is life on the planet, it is affected by this radiation, but it is pure speculation as to what kind of effect it has.
Although Proxima b is in the habitable zone of its star and there may be liquid water on the surface, it does not mean that it is actually habitable. And the radiation it is likely to be exposed to has probably removed key elements of life such as hydrogen, oxygen and nitrogen.
The newly discovered planet is fascinating, as further studies could show how low-mass planets form around low-mass stars, the researchers said. And this particular planet throws the typical theory of the formation of super earth planets on the head.
It is beyond the “snow line” of the system, suggesting that any water on the planet would be frozen. Super-earths usually form near the snow line, but not beyond.
“The formation of a super-earth far beyond the snow line questions formation models according to which the snow line is a sweet spot for the accumulation of super-earths due to the accumulation of icy solids here,” said Mario Damasso, study author and postdoctoral fellow at the Italian National Institute for astrophysics. “Or it suggests that the protoplanetary disk was much warmer than normal. In general, nothing hinders the existence of Proxima c where we discover it, but the story of its origins and evolution is an issue that should be examined in more detail. “
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.
“Proxima Centauri is the closest star to the sun, and this discovery would make it the closest multi-network system,” said Del Sordo.