An artist's impression of Barnard b. Image: ESO/M Kornmesser
Barnard b is one of the lowest-mass exoplanets known and one of the few with a mass less than that of Earth.
Astronomers have discovered the existence of a new exoplanet orbiting Barnard’s star, the second closest stellar system to Earth.
The discovery of Barnard b, as the exoplanet is called, is the result of five years of observations using the European Southern Observatory’s (ESO) Very Large Telescope (VLT) situated at the Paranal Observatory in Chile.
The astronomers also found this exoplanet – a planet outside our solar system – orbits 20 times closer to its star (Barnard’s star) than Mercury does around the sun. As a result, the surface on Bernard b is extremely hot, at around 125 degrees Celsius.
“The planet is too close to the host star, closer than the habitable zone,” said Jonay González Hernández, a researcher at the Instituto de Astrofísica de Canarias in Spain, who wrote about the discovery his team made in a scientific paper published in the Journal Astronomy & Astrophysics today (1 October).
“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 proximity to its star also means that a year on Barnard b would be about 3.15 Earth days.
The promise of an exoplanet orbiting Barnard’s star was first detected in 2018, but were not confirmed until now.
“Even if it took a long time, we were always confident that we could find something,” said González Hernández.
Barnard’s star, named after astronomer Edward Emerson Barnard, is a cool, low-mass red dwarf – a star that has relatively low pressures, a low fusion rate and low temperature. This helps the star stay alive for much longer as opposed to a yellow dwarf like our sun.
The temperate zones for red dwarfs are much closer to the star than that of hotter stars like the sun, which means they have shorter orbital perdiods. This means scientists are able to observe them over several days or weeks, rather than years.
Astronomers said that Barnard b has half the mass of Venus. “Barnard b is one of the lowest-mass exoplanets known and one of the few known with a mass less than that of Earth,” González Hernández said.
To make such detailed discoveries, the research team used ‘Espresso’, a highly precise instrument on the VLT designed to measure the wobble of a star caused by gravitational pulls of one or more orbiting planets.
“We now need to continue observing this star to confirm the other candidate signals,” said Alejandro Suárez Mascareño, a researcher at the Instituto de Astrofísica de Canarias and co-author of the study.
However, he added that the discovery of this planet “shows that our cosmic backyard is full of low-mass planets”.
In addition to Barnard b, the team of astronomers also found the possibility of three more exoplanets orbiting Barnard’s star but will require additional observations to be confirmed.
The European Southern Observatory is in the process of constructing an Extremely Large Telescope, which would potentially help researchers to detect more small, rocky planets and allow them to study their compositions.
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