Discovery of new exoplanet orbiting Barnard's star reshapes search
An international team of scientists using the Very Large Telescope (VLT) in Chile has discovered an exoplanet orbiting Barnard's Star, the closest single star to the Solar System.
Barnard's Star is located at a distance of about 6 light years from Earth, making it the second closest star system after the Alpha Centauri triple system, which is a little over 4 light years away. Around Proxima Centauri, one of the stars in that system, there orbits one confirmed planet and two potential ones. The proximity of Barnard’s Star makes it an attractive target for searching for Earth-like planets.
In 2018, the discovery of a planet in the Barnard's Star system was announced, but later studies did not confirm this. The latest observations also rule out the previous planet, instead detecting another one, along with three more candidates.
The research was conducted over five years using the Very Large Telescope (VLT) at the Paranal Observatory in Chile, which belongs to the European Southern Observatory (ESO). The scientists, led by Jonay González Hernández from the Instituto de Astrofísica de Canarias in Spain, focused on searching for signals from potential planets orbiting in the habitable zone of Barnard's Star.
The habitable zone is the area around a star where conditions could allow liquid water to exist on a planet's surface. It is also called the ecosphere, the habitable zone, or, poetically, "the Goldilocks zone." This refers to the tale of Goldilocks and the Three Bears, in which the girl chooses among three objects the one that is “just right,” discarding the others as too large or small, too hot or cold.
Barnard's star — what do we know about it?
Barnard's Star is a red dwarf with a mass, size, brightness, and temperature smaller than the Sun. Such stars are often selected for searching small rocky planets because they are easier to detect. A red dwarf is cool, and its habitable zone is closer, meaning that planets have shorter orbital periods. Additionally, the smaller mass of the star makes the planet's gravitational influence on the star's motion more pronounced.
The newly discovered planet, Barnard b, orbits 32 million kilometres closer to its star than Mercury is to the Sun. Its orbital period is 3.15 Earth days—that's how long a year lasts there. The surface temperature reaches 125 degrees Celsius, which is too high for liquid water to exist. The planet's mass is about 37 percent of Earth's mass, making it almost three times the mass of Mars.
The research findings were published on Tuesday in the journal "Astronomy and Astrophysics." The project involved scientists from Spain, Portugal, Switzerland, Italy, the USA, Germany, and Chile. They used the highly accurate ESPRESSO spectrograph for observations, and the obtained data were confirmed with other instruments: HARPS at the La Silla Observatory (also ESO), HARPS-N, and CARMENES.
