Barnard's star revelation: Four newfound planets stun scientists
Scientists have discovered four planets orbiting Barnard's Star, the closest solitary star to Earth, located 5.96 light-years away. "It's a really exciting find—Barnard's Star is our cosmic neighbor, and yet we know so little about it," says Ritvik Basant from the University of Chicago, the lead author of the study.
Astronomers have long sought planets around Barnard's Star, the nearest solitary star to the Sun, discovered in 1916. After years of uncertain signals, a team led by Ritvik Basant from the University of Chicago confirmed the existence of four planets. This is a groundbreaking discovery because all these planets are smaller than Earth.
New discoveries in the Barnard's Star system
Barnard's Star, also known as GJ 699, is a star in the Ophiuchus constellation, an extremely faint red dwarf located about 6 light-years from the Sun, making it an interesting object of study. It is the nearest single star system to Earth. Thanks to its proximity to our planet, studies on it can provide valuable information about planetary systems around red dwarfs. The discovery of four planets around this star marks a significant step forward in exoplanet research.
Scientists used the Gemini North telescope, part of the International Gemini Observatory. The Basant team used the MAROON-X instrument on the Gemini North telescope in Hawaii to observe the star over 112 nights. By analyzing the data, scientists detected subtle shifts in the star's position, confirming the presence of planets. The study results were published in "The Astrophysical Journal Letters." Basant noted that observations were made at different times of the night on different days, and teams in Chile and Hawaii did not coordinate their actions, which provides high confidence that these are not data errors.
The new exoplanets are rocky, not gaseous like Jupiter
One of these planets is the least massive exoplanet discovered so far using the radial velocity technique, which sets a new benchmark in the search for smaller planets around nearby stars. The newly discovered planets are most likely rocky, rather than gaseous like Jupiter. However, it will be difficult to confirm this with certainty, because from Earth's perspective, these planets do not transit their star, which is the usual method for determining a planet's composition. The team will, however, be able to better estimate their composition by using information on similar planets around other stars.
The team was able to exclude with high confidence the existence of other exoplanets with masses comparable to Earth in the habitable zone of Barnard's Star — the area around the star suitable for the existence of liquid water on the planet's surface.
Unique challenges in the search for exoplanets
The discovery of planets around Barnard's Star highlights how difficult it is to detect small exoplanets. These planets are too close to the star to be habitable, as temperatures are too high for liquid water. Nonetheless, discovering the smallest planet of Barnard's, with a mass of just 0.19 times Earth's mass, is a significant achievement.
This research underscores how easily small exoplanets can be overlooked, even when they are nearby. The discovery of the Barnard system suggests that the lack of Earth-like planets may stem from the difficulty in detecting them. "It's a really exciting find—Barnard's Star is our cosmic neighbor, and yet we know so little about it," conveyed Ritvik Basant, a Ph.D. student at the University of Chicago and lead author of the study published in "The Astrophysical Journal Letters," in a statement, emphasizing the importance of this breakthrough.
The four planets, each with a mass of only 20 to 30% of Earth's mass, are so close to their star that they orbit it within a few days. The fourth planet is the least massive planet discovered so far using the radial velocity technique. The team hopes that this discovery will usher in a new era of finding an increasing number of exoplanets with masses smaller than Earth's in the universe.
The majority of rocky planets discovered so far are much larger than Earth and seem quite similar throughout the Milky Way. However, there are reasons to believe that smaller exoplanets have more diverse compositions. As scientists discover more of them, they can begin to gather more information about how these planets form and what makes them potentially habitable.
