After decades of controversy and canceled discoveries, astronomers have managed to confirm the presence of exoplanets in one of the Sun’s closest neighbors. It’s about Barnard’s star.
“White whale” of exoplanet hunters
Barnard’s star is located 6 light-years away from Earth. Only the Alpha Centauri triple system is closer to us. Barnard’s star is a solitary red dwarf with a radius 18% of the Sun’s radius and a mass 15% of the Sun’s mass. It emits about 250 times less light than our star. Therefore, despite its proximity, it cannot be seen with the naked eye in the earthly sky.
Scientists have long tried to find exoplanets near Barnard’s star. The first sensational claims of their discovery were made back in the 1960s, but later refuted. Subsequently, various groups of astronomers have also made statements about finding signs of exoplanets in the Barnard system — and each time they have not been confirmed. Because of this, some scientists have figuratively begun to compare them to the white whale from Moby Dick.
Finally, last year, researchers from the European Southern Observatory managed to prove that Barnard’s star has exoplanets. They managed to find a world with half the mass of Venus, having an orbital period of 3.15 days. The data obtained by astronomers also hinted at the presence of three more exoplanets, but it was not possible to confirm their existence at that time and they remained on the list of candidates.
Four exoplanets in Barnard’s star
To finally understand how many exoplanets orbiting around Barnard’s star, astronomers used the MAROON-X instrument installed on the Gemini North telescope. It is designed to search for worlds in red dwarf systems by measuring radial velocities.
In total, MAROON-X observed Barnard’s star for 112 nights over three years. After analyzing the data it collected, astronomers were able to confirm the existence of three exoplanets.
According to the researchers, all four worlds of Barnard’s star are rocky bodies like our own. Their masses lie between 19% and 34% of the Earth’s mass. The fourth exoplanet is the least massive exoplanet discovered to date using the radial velocity method. Unfortunately, none of these worlds are transiting, which prevents us from estimating their diameter and determining the presence of an atmosphere.
The orbits of all four exoplanets lie outside the habitable zone. They pass too close to the star for water to exist on them. The available data also rules out the presence of planets with masses greater than 0.57 Earth masses in the habitable zone of Barnard’s star, although smaller bodies are still possible there.
In conclusion, it is worth saying that the Barnard star system is remarkably compact. The orbital periods of the exoplanets are 2.34; 3.15; 4.12 and 6.74 days. Can such a system be stable? Using a machine learning algorithm, astronomers have found that if the planets have perfectly circular orbits, the system is stable in the long term. However, using more likely orbital parameters, the system becomes unstable in just 2,000 years. Therefore, additional observations are needed to better understand its long-term dynamics.
According to aasnova.org
