Astronomers have discovered a planet orbiting Barnard’s Star, a star located six light years away from the Sun, making it one of the closest stars to our solar system. Named “Barnard’s Star b”, the planet is thought to have over three times the mass of Earth’s. This places it in a category of planets known as “super-Earths.”
Guillem Anglada Escudé of the School of Physics and Astronomy at the University of London writes in the journal Nature that Barnard’s Star b is a “cold super-Earth”. Despite being described as cold, the planet is the same distance from Barnard’s Star as Mercury is from our own Sun. However, unlike the Sun, Barnard’s Star is a Red Dwarf, meaning it has a much lower temperature than the Sun. The star is only three percent as bright as the Sun.
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It is currently estimated that the newly discovered planet has a surface temperature of -150°C. However, it has been hypothesized that the planet has a massive atmosphere held together by the gravity it has thanks to its enormous size. This large atmosphere could potentially warm the planet’s surface temperature, making conditions more hospitable to life as well.
Astronomers used the radial velocity method to detect the planet. This technique detects “wobbles” in a star caused by the gravitational pull of an orbiting planet. The existence of Barnard’s Star b was confirmed after the astronomers re-examined archived data obtained over two decades. They also took into consideration new observations taken with the Carmenes spectrometer in Almeria, Spain, the Eso/Harps instrument in Chile and the Harps-N instrument in the Canary Islands.
Barnard’s Star b is the smallest planet ever discovered using the radial velocity method.
In the 1960s, Dutch astronomer Peter Van de Kamp published evidence of the existence of a planet orbiting Barnard’s Star. However, other scientists were unable to reproduce his findings.
“The new planet is impossible for Peter van de Kamp to have detected. The signal would have been too small for the technique he was using”, Escudé told BBC News.