Barnard is a red dwarf star with a special feature: It’s the closest star to the Solar System, which means it moves independently of a stellar system. Recently, a group of astronomers discovered it has a planet similar to ours in its orbit.
The discovery. A team of Spanish scientists published their findings in Astronomy & Astrophysics. The paper describes an exoplanet orbiting Barnard, which they named “Barnard b.” This discovery was made after five years of observational data taken with the European Southern Observatory’s Very Large Telescope at the Paranal Observatory in Chile.
A hint. The team was initially searching for exoplanets within Barnard’s habitable zone, where liquid water could exist on a planet’s surface. However, scientists concluded that Barnard’s star is less powerful than the Earth’s Sun, so the newly discovered exoplanet isn’t within the habitable zone and can’t support life as we know it.
The recent discovery builds on previous indications of a potential planetary signal orbiting the star. In 2018, a different group of experts estimated that the hypothetical exoplanet was approximately three times the mass of Earth. They also discovered the orbit to be at a distance of around 0.4 astronomical units.
The star. Barnard, also known as GJ 699, is of significant interest to planetary astronomers. It’s one of the closest stars to Earth, aside from the Centauri trinary system. Unlike the Sun, Barnard isn’t just a solitary star. It’s a red dwarf, which is the most common type of star in the galaxy, situated approximately six light-years from Earth.
This is why researchers are particularly interested in studying it. It can provide valuable insights into the galaxy we live in, the planets and planetary systems surrounding single stars and red dwarfs, and the potential habitability of these systems.
Searching for exoplanets. Naturally, it’s much harder to find smaller exoplanets than larger ones. What’s crucial is what they reveal. Astronomers typically detect exoplanets by observing their impact on their host stars: The larger the exoplanet, the more noticeable the effect.
The challenge arises when dealing with smaller exoplanets orbiting smaller stars, like tiny red dwarfs. In such cases, astronomers can detect signals from smaller exoplanets compared to what they could detect around larger stars. Additionally, Barnard is close to Earth, making it easier to observe than a more distant and, therefore, fainter star.
Eureka! Scientists obtained interesting data using the Very Large Telescope. Specifically, it showed a motion with a periodicity of 3.15 days. What does this mean? It suggests that the Barnard b exoplanet is orbiting the star every 3.15 Earth days. Additionally, the motion’s depth indicates that the exoplanet’s mass is at least about 0.37 times the mass of Earth.
Due to its proximity to its star, the exoplanet experiences turbulence and has a surface temperature of about 260 degrees Fahrenheit. According to Jonay González Hernández, a researcher at the Institute of Astrophysics of the Canary Islands in Spain and author of the study, “Barnard b is one of the lowest-mass exoplanets known and one of the few known with a mass less than that of Earth.”
There’s more. Alejandro Suárez Mascareño, also a researcher at the institute and co-author of the study, said, “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.”
In the paper, researchers say that there’s evidence for at least three more exoplanet candidates around the Barnard star. However, more observations are needed to confirm whether any of them are actual exoplanets.
Image | ESO | M. Kornmesser, Alysa Obertas | Wikimedia Commons, CC BY-SA 4.0
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