Closest Barnard’s Star Found to Have Four Small Planets

Astronomers have confirmed the existence of four planets orbiting Barnard’s Star, the closest single star to Earth or the second closest star system, located 6 light-years away. This discovery comes after a study published last year revealed a planet smaller than Earth orbiting the star. This recent confirmation indicates that there are not just one, but a total of four planets orbiting Barnard’s Star.

Barnard’s Star, a red dwarf star with a small mass located remarkably close to the solar system, has long been a focus of astronomers in the search for Earth-like planets since its discovery in 1916. Compared to the Alpha Centauri system in the constellation of Centaurus, which is only 4.4 light-years away from the Sun, Barnard’s Star holds the distinction of being the closest star system to our solar system. Alpha Centauri comprises three stars – Alpha Centauri A, Alpha Centauri B, and Proxima Centauri.

In terms of individual stars, Barnard’s Star ranks as the fourth closest star to the Sun, following the three stars of Alpha Centauri. A study published in the journal Astronomy & Astrophysics on October 1, 2024, identified a planet orbiting Barnard’s Star named Barnard b, with indications of potentially three additional planets on different orbits around the star.

On March 11, the University of Chicago released a press statement confirming the existence of these four planets, led by astronomers from the university. Each of these planets has a mass only 20% to 30% of Earth’s mass and orbits very close to Barnard’s Star, with rotation periods lasting just a few days. Although these planets may not be suitable for habitation due to their proximity to the star resulting in high temperatures, the discovery sets a new standard for finding smaller planets near stars.

The lead author of the study, doctoral student Ritvik Basant, expressed excitement about this finding, emphasizing the significance of Barnard’s Star as a neighbor in the cosmos, shedding light on the advancements in instrumentation precision. However, due to their small size and close proximity to their host star, observing these planets proves challenging even with the most powerful telescopes, requiring astronomers to employ creative methods to locate them.

To address this challenge, the research team led by Professor Basant developed the MAROON-X instrument specifically designed for detecting distant planets and installed it at the Gemini Telescope in Hawaii. By meticulously calibrating and analyzing 112 days of data collected over three years with MAROON-X, researchers confirmed the presence of three planets orbiting Barnard’s Star.

Furthermore, combining the data from MAROON-X with observations from the ESPRESSO instrument on the European Southern Observatory’s Very Large Telescope led to the final confirmation of a fourth planet around Barnard’s Star. Scientists speculate that these planets are potentially rocky planets rather than gas giants like Jupiter, although definitive confirmation remains difficult given the limitations in our ability to observe them passing in front of the star from Earth.

The discovery of these planets signifies one of the smallest planets found to date through this observational technique. Scientists hope that this discovery will usher in a new era of uncovering increasingly diverse planets in the universe, providing insights into their formation and conditions conducive to life.

Researchers highlight that most rocky planets discovered so far are significantly larger than Earth and appear similar across the galaxy. However, there is reason to believe that smaller planets may exhibit a broader range of composition. As more of these planets are discovered, scientists can begin unraveling more information about how these planets form and the factors influencing their potential habitability.

These research findings were published on March 11 in The Astrophysical Journal Letters, marking a significant contribution to the ongoing exploration of planets beyond our solar system.