A super-Earth orbits a famous star not far from our sun

The rocky planet, at least 3.2 times the size of Earth, is orbiting Barnard's Star, one of the closest and most well studied red dwarf stars in the Galaxy and the sun's nearest neighbouring single star. That's much closer than Earth to the Sun (about 0.4 times the distance), but Barnard's Star is such a dim bulb that the planet only receives about 2% as much light as Earth does, so it's very, very cold. "We just don't know". After analyzing the archives of the last 20 years of observations of Barnard's star, produced by members of the Pale Red Dot, and examining it with HARPS and other instruments over the past two years, scientists have found a "99% of hints" for the existence of the planet from the star. The analysis that led to the discovery is detailed in a study published Wednesday in the journal Nature. The newly discovered planet is the second-closest known exoplanet to the Earth and orbits the fastest moving star in the night sky.

Ribas, who is the director of the Institute of Space Studies of Catalonia and a research at Spain's Institute of Space Sciences, noted that there have been many previous searches for planets around Barnard's Star, and even announcements of discoveries.

Barnard's star b, as the new planet is called, was excruciatingly hard to pin down, and the team is referring to it as a "candidate planet" though it is confident it's there. In 2016, astronomers using ESO telescopes and other facilities found clear evidence of a planet orbiting the closest star to Earth in this system, Proxima Centauri.

The physical motion of the star is far too small to detect. Its average surface temperature is possibly a brisk -150 degrees Celsius (-238 degrees Fahrenheit).

An artist's illustration shows what of the exoplanet orbiting Barnard's Star might look like on the surface.

The Jupiter-mass planets around Barnard's star were no more. This means we can begin to put our own solar system in context, and draw informed conclusions about just how special the Earth is. Teams of semi-professional astronomers coordinated by the American Association of Variable Star Observers also contributed to the detection. This places it in the "snow line" of the star, where it's cold enough for water to freeze into solid ice.

Still, over the years, a lot of astronomers have observed Barnard's Star. With the Doppler effect, as a planet orbits a star, the planet's gravitational pull causes its star to wobble a little bit. "We followed Barnard's star for 16 long years at Keck, amassing some 260 radial velocities of Barnard's star by 2013", said Vogt. More recently, most exoplanets have been detected using a different technique known as the transit method.

Part of the challenge of finding the planet comes from the method that astronomers used: radial velocity (RV). It worked only for the nearest stars and was achieved by taking photographs of the star and measuring its positions in relation to one another.

The center of the image shows Barnard's Star captured in three different exposures.

"At a distance of only six light years, Barnard's Star b could conceivably be visited by people from Earth".

Professor Hugh Jones, from the University of Hertfordshire and a co-author on the paper, said: "The announcement of the planet has been a long time in the making; initial observations of the planet were made by Dr Paul Butler at the Carnegie Institution of Washington in June 1997".

  • Valerie Cook