Artist’s impression of Barnard’s star b, a planet in orbit around Barnard’s star
ESO/M. Kornmesser
One of the sun’s closest neighbours, Barnard’s star, appears to have at least one planet orbiting it, as well as another three possible planets that need further confirmation.
Astronomers have been looking for planets around Barnard’s star, which at 5.96 light years away is the next-closest star to us after the three stars in the Alpha Centauri system, since the 1960s.
In 2018, researchers claimed to have found a planet that was at least three times larger than Earth, which they called Barnard’s star b, but a follow-up analysis showed that the signals of the apparent planet were actually caused by higher than expected stellar activity.
Now, Jonay González Hernández at the Canary Islands Institute of Astrophysics and his colleagues say they have found a new Barnard’s star b, which is around 40 per cent as massive as Earth.
The planet is much closer to its star than any planets in our solar system, completing an orbit in just over three Earth days. This also means its surface is too hot for liquid water or life, with a temperature of around 125°C (257°F).
González Hernández and his team found the star by watching for tiny wobbles in the position of Barnard’s star caused by the gravity of its orbiting planet, using an instrument on the European Southern Observatory’s Very Large Telescope in Chile called ESPRESSO.
They also found evidence for three more planets orbiting the star. However, the signals weren’t strong enough to say for certain, so they will need further observations to confirm it.
“These are very tricky detections, and it’s always hard because you have the activity of the star, the stellar magnetic fields, which are rotating with the star,” says Rodrigo Fernando Díaz at the National University of San Martín in Argentina. González Hernández and his team have been thorough in checking that their observations were from a planet, but there could always be “unknown unknowns”, says Fernando Díaz. Truly confirming this will require data from another telescope, which could take years of observations, he says.
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