Scientists say it is possible that the Alpha Centauri system, the closest planetary system to Earth, contains habitable exoplanets.
In a study published in the Astronomical Journal, researchers looked through old data to narrow down the chances of different sized planets around the three stars – Alpha Centauri A, B, and Proxima Centauri, located 4.2 light-years from us.
So far we know of one planet around one of these stars, Proxima b, although there have been other false alarms. This was found using the radial velocity method, noticing the tug on the star from the planet as it orbits.
But our methods aren’t sensitive enough yet to find more planets in this way. So this team of scientists from the US and China used existing data to rule out what sort of planets we might find in the future.
As such, they’re pretty certain we will not find any exceptionally large planets in the system, suggesting we’re more likely to find smaller planets. They suggest that Alpha Centauri A could contain planets smaller than 50 Earth masses, for B it’s 8 Earth masses, and for Proxima its 0.5 Earth’s mass.
“The universe has told us the most common types of planets are small planets, and our study shows these are exactly the ones that are most likely to be orbiting Alpha Centauri A and B,” said Professor Debra Fischer from Yale University, one of the study’s co-authors, in a statement.
Proxima b is the only planet we know of in this system so far. ESO/M. Kornmesser
The data came from an array of instruments in Chile. Based on the information available so far the researchers concluded that if there were habitable planets around one of these stars, we wouldn’t have been able to detect them yet.
“This is a very green study in that it recycles existing data to draw new conclusions,” Lily Zhao from Yale University, the study’s lead author, said in a statement.
“By using the data in a different way, we are able to rule out large planets that could endanger small, habitable worlds and narrow down the search area for future investigations.”
It may be several years until our data is sensitive enough to detect planets around these stars. But as they are so close, they are of huge scientific and public interested – so narrowing down what we might expect to find is key.