Discovery of the 1st known exoplanet orbiting Barnard’s star. Video via ESO.
- Barnard’s star is the closest single star to our sun, at only 6 light-years away. Only the Alpha Centauri system of three stars is closer.
- There is at least one planet orbiting Barnard’s star, an international team of astronomers has confirmed. It is about half the mass of Venus and orbits very close to its star. A previous candidate planet found in 2018 was never confirmed.
- There may be at least three more planets orbiting Barnard’s star. But more observations will be needed to confirm them.
Exciting news! Six months ago, just as we were ending our spring fundraiser, EarthSky received a $50,000 gift, with a request that it be used to collect matching funds. Whoa! We were so thrilled and grateful. And now it’s time to make good on our obligation. Please help us meet this match by donating to EarthSky today!
A new planet in the neighborhood!
Barnard’s star is the closest single star to our sun, only 6 light-years away. Despite being so nearby, astronomers didn’t know for sure if it had any planets orbiting it. But now, we know it has at least one. An international team of astronomers using the European Southern Observatory’s Very Large Telescope (VLT) in Chile said on October 1, 2024, that they have confirmed a planet about half the mass of Venus. The planet, dubbed Barnard b, completes an orbit around the red dwarf star in only 3.15 Earth days.
The researchers published the peer-reviewed discovery in the journal Astronomy & Astrophysics on October 1, 2024.
Discovery of 1st known planet orbiting Barnard’s star
The discovery comes after five years of observations with the Very Large Telescope at Paranal Observatory in Chile. Astronomers had made a tentative detection of a small planet around Barnard’s star back in 2018, orbiting once every 233 days, but it was never confirmed. The new observations, although they took five years to complete, were worth it. Lead author Jonay González Hernández at the Institute of Astrophysics of the Canary Islands in Spain, said:
Even if it took a long time, we were always confident that we could find something.
The astronomers were looking for possible planets in or close to the habitable zone around Barnard’s star. That’s the distance where temperatures could allow liquid water to exist. Such planets are easier to find around red dwarf stars – and indeed seem to be common – since those stars are less bright than stars like our sun.
The astronomers also said the newly discovered exoplanet is not the same as the previous candidate from 2018.
A hot world
Barnard b is a bit too close to its star to be habitable by earthly standards, however. It orbits its star 20 times closer than Mercury orbits the sun. It takes only 3.15 days to orbit the star. Even though Barnard’s star is a lot cooler than the sun, that is still too close for comfort. Barnard b has an estimated surface temperature of 257 degrees Fahrenheit (125 C). As Hernández noted:
Barnard b is one of the lowest-mass exoplanets known and one of the few known with a mass less than that of Earth. But the planet is too close to the host star, closer than the habitable zone. Even if the star is about 2,500 degrees cooler than our sun, it is too hot there to maintain liquid water on the surface.
The researchers used an instrument on the telescope called ESPRESSO to find the planet. ESPRESSO detects exoplanets using the radial velocity method. In this method, a telescope measures the tiny “wobble” a star makes as the planets’ gravitational pull tugs at the star. In addition, three other instruments elsewhere helped to confirm the planet: HARPS at ESO’s La Silla Observatory, HARPS-N and CARMENES.
Animation of a sub-Earth-mass planet orbiting Barnard’s star. Video via ESO/ M. Kornmesser.
More planets?
Intriguingly, there may be more planets in the Barnard’s star system as well. The research team found hints of at least three more planets orbiting Barnard’s star. These, however, will require more observations to confirm if they really are planets. Co-author Alejandro Suárez Mascareño, also at the Institute of Astrophysics of the Canary Islands, said:
We now need to continue observing this star to confirm the other candidate signals. But the discovery of this planet, along with other previous discoveries such as Proxima b and d, shows that our cosmic backyard is full of low-mass planets.
The paper stated:
Confirming the presence of a compact four-planet system orbiting Barnard’s star, similar to other planetary systems orbiting nearby stars, would require many more ESPRESSO observations.
The discovery, along with other planets – both small and large – around other nearby stars, shows that smaller rocky worlds are common in our galaxy. Could any of them support life? We don’t know yet, but the more we find, the closer we get to answering the long-standing question: “Are we alone?”
Bottom line: Astronomers have confirmed a small exoplanet orbiting Barnard’s star, the closest single star to our sun. There are hints of at least 3 more planets as well.
Source: A sub-Earth-mass planet orbiting Barnard’s star
Via ESO
Read more: The enduring mystique of Barnard’s Star
Read more: Primitive life at Barnard’s Star?