Astronomers have discovered a planet orbiting the closest solo star to Earth.
The solo star, which is known as Barnard’s star, is a red dwarf which is around 80% smaller than our sun and sits around six light years away from our solar system.
The newly discovered planet, dubbed Barnard b, has half the mass of Venus, and a year on it lasts slightly more than three Earth days.
The astronomers published their findings in the journal Astronomy & Astrophysics.
Using the European Southern Observatory’s Very Large Telescope (ESO’s VLT), the researchers also suggest that there could be three more exoplanets that orbit the star.
However, the researchers are sure there is no life on Barnard b as it sits twenty times closer to Barnard’s star than Mercury is to the Sun, and therefore has a surface temperature of a blisteringly hot 125°C.
Despite Barnard’s star being the single closest solo star to us, the exoplanet is not the closest one to Earth. The closest stellar system to Earth is the three star group of Alpha Centauri, which hosts the planet Proxima Centauri b and is around four light years away.
Researchers were excited to find this planet, as no planet orbiting Barnard’s star has been discovered until now – and due to its proximity to Earth, it is a primary target in the search for Earth-like exoplanets.
The team are particularly interested in rocky worlds in the habitable zone around this close star.
This region, also known as the ‘Goldilocks zone’, is special because it is the area around a star that is neither too hot nor too cold for water to exist on an orbiting planet without boiling away or freezing. And if there is liquid water, among other things, there may be life.
Barnard b was discovered as a result of observations made over five years using the VLT, which is located in Chile.
Using a highly precise instrument called ESPRESSO (the Echelle Spectrograph for Rocky Exoplanet and Stable Spectroscopic Observations), the team measured the wobble of a star which is caused by the gravitational pull of one more orbiting planets to find Barnard b.
Then, when the researchers thought they had found something, they confirmed their findings by using data from the exoplanet-hunting High Accuracy Radial Velocity Planet Searcher (HARPS).
What is an exoplanet and how are they found?
- The eight planets in our solar system orbit around the Sun. Planets that orbit around other stars are called exoplanets
- These planets are very hard to see directly with telescopes. They are hidden by the bright glare of the stars they orbit
- Astronomers search for exoplanets by looking for ‘wobbly stars’, which is a star that has planets which don’t orbit perfectly around its center. From far away, this off-center orbit makes the star look like it’s wobbling
- Another method, used to look for smaller Earth-sized planets, is the transit method. When a planet passes in front of its star, it’s called a transit and as the planet transits in front of the star, it blocks out some of the star’s light, making the star look a little less bright
The researchers were looking for signals from possible exoplanets within the habitable or temperate zone of Barnard’s star, which is the range where liquid water can exist on the planet’s surface. Red dwarfs like Barnard’s star are often targeted by astronomers since low-mass rocky planets are easier to detect there than around larger Sun-like stars.
Lead author Dr Jonay González Hernández said: ‘Even if it took a long time, we were always confident that we could find something.
‘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 2500 degrees cooler than our Sun, it is too hot there to maintain liquid water on the surface.’
This exciting finding offers a huge range of untapped possibilities in the search for life outside Earth. So what’s next?
Co-author Dr Alejandro Suárez Mascareño 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.’
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