- Barnard’s Star is the closest single star to our sun, at only 6 light-years away. For decades, astronomers have been saying it might have a planet. Now a planet has been found.
- There’s at least one planet orbiting Barnard’s Star, an international team of astronomers has confirmed. The confirmed planet is about half the mass of Venus and orbits very close to its star, with a “year” only three days long.
- And there might be at least three more planets orbiting Barnard’s Star. That’s super exciting, because Barnard’s Star is so nearby!
A confirmed planet for Barnard’s Star
Barnard’s Star is the closest single star to our sun, only 6 light-years away. (Yes, the Alpha Centauri system is closer. But it consists of at least two and probably three stars.) Despite being so nearby – and despite decades of speculation – astronomers had not yet confirmed a planet obiting Barnard’s Star. 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.
Barnard’s Star in popular culture
Why is a planet for Barnard’s Star so exciting? The star is nearby. And it’s single, like our sun. As long ago as the 1960s and ’70s – long before successful planet-hunters like the Kepler spacecraft – there were suggestions that Barnard’s Star might have a family of planets. At that time, reported discrepancies in the motion of the star led to a claim that at least one Jupiter-size planet, and possibly several planets, orbit it. But later evidence disputed the claim.
Then, in November 2018, an international team of astronomers announced it was “99% confident” that a planet for Barnard’s Star had been found. Yet that discovery, too, seemed to evaporate when, in 2021, additional work refuted the existence of this planet.
The long-standing rumor of planets for Barnard’s Star secured this star’s place in science fiction. It’s featured in, for example, The Hitchhiker’s Guide to the Galaxy by Douglas Adams; The Garden of Rama by Arthur C. Clarke and Gentry Lee; and several novels of physicist Robert L. Forward. In these works, the fictional planets of Barnard’s Star are locations for early colonization or waystations for exploration further into the cosmos.
Barnard’s Star also was the hypothetical target of Project Daedalus, a design study by members of the British Interplanetary Society, in which they envisioned an interstellar craft that could reach its destination within a human lifetime.
And Barnard’s Star has been featured in online games.
Clearly, Barnard’s Star captures peoples’ imaginations!
How they confirmed the new planet
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 astronomers emphasize that the newly discovered exoplanet is not the same as the 2018 candidate.
The discovery comes after five years of observations with the Very Large Telescope at Paranal Observatory in Chile. The new observations were worth it, these astronomers said. Lead author Jonay González Hernández at the Institute of Astrophysics of the Canary Islands in Spain, explained:
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.
Discovery of the 1st known exoplanet orbiting Barnard’s Star. Video via ESO.
It’s hot, hot, hot!
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 260 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’ gravity 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 three more planets as well.
Source: A sub-Earth-mass planet orbiting Barnard’s star
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