Astronomers have just found a planet orbiting around one of the closest stars to the Sun, Barnard’s Star. It is at least three times as massive as our own.
Barnard’s Star, a dim red dwarf, lies just 6 light-years from the sun in the constellation Ophiuchus. It is the closest neighbor to us, apart from the three-star Alpha Centauri system, which is about 4.3 light-years away.
The newfound planet, known as Barnard’s Star b, orbits its host star once every 233 days.
However, astronomers have long suspected there could be a planet around Barnard’s star due to the high frequency of planets around M dwarf stars revealed by NASA’s now-defunct Kepler space telescope.
The alien world remains a planet candidate for now. But astronomers who identified it are confident the alien planet will eventually be confirmed.
“After a very careful analysis, we are 99 percent confident that the planet is there,” Ignasi Ribas, of the Institute of Space Studies of Catalonia and the Institute of Space Sciences in Spain, said in a statement.
“However, we’ll continue to observe this fast-moving star to exclude possible, but improbable, natural variations of the stellar brightness which could masquerade as a planet,” added Ribas, the lead author of a new study announcing the detection of Barnard’s Star b. The researchers published the study online today (Nov. 14) in the journal Nature.
The planet lies in a distant region from the star, known as the ‘snow line’. This is beyond the habitable zone in which liquid water, and possibly life, could exist.
The researchers estimate the planet’s surface temperature to be around -170 degrees Celsius. Therefore, it is likely to be a frozen world and not so welcoming to Earth-like life. But if the planet has a substantial atmosphere the temperature could be higher and conditions potentially more hospitable.
The new investigation combines both new and archival observations spanning 20 years from seven different instruments across the globe.
The data record the star’s radial velocity, its relative speed toward and away from Earth. This technique detects wobbles in a star which are likely to be caused by the gravitational pull of an orbiting planet. As the star moves towards the Earth its spectrum appears slightly shifted towards the blue and, as it moves away, it is shifted towards the red.
This is the first time that astronomers have used this technique to detect a planet this small so far away from its host star.
The researchers also detected hints of another possible planet in the system. The other object is orbiting way farther out than Barnard’s Star b with an orbital period of 6,600 Earth days. But this second signal is too weak for scientists to consider it a planet candidate, Teske said.
Thumbnail image: Artist’s impression of the surface of Barnard’s star b. Credit ESO-M. Kornmesser. Credit: Credit ESO-M. Kornmesser