Astronomers have discovered four small planets orbiting Barnard’s Star, the second-nearest star system to Earth. Each planet is about 20 to 30% the mass of Earth and orbits closely around its star, completing a revolution in just days. Due to their proximity to Barnard's Star, these planets are likely too hot for habitation.
Ritvik Basant, a Ph.D. student at the University of Chicago and lead author of the study, remarked on the significance of this discovery: “It’s a really exciting find—Barnard’s Star is our cosmic neighbor, and yet we know so little about it.” This research marks progress in detecting smaller planets around nearby stars.
The study adds credibility to a previous November finding that suggested the presence of one planet and hinted at others around Barnard’s Star. Published on March 11 in The Astrophysical Journal Letters, this new research involved scientists from Gemini Observatory/National Science Foundation NOIRLab, Heidelberg University, and the University of Amsterdam.
Jacob Bean from UChicago led an effort using MAROON-X, an instrument designed to detect distant planets by observing gravitational effects they exert on their host stars. After analyzing data over three years, his team confirmed three planets orbiting Barnard’s Star. When combined with data from ESPRESSO at Chile's Very Large Telescope, evidence for a fourth planet emerged.
While it remains challenging to confirm whether these are rocky planets due to observational limitations from Earth, researchers believe they are more likely rocky than gaseous like Jupiter. The team ruled out other potential habitable zone planets around Barnard's Star with reasonable certainty.
Basant emphasized the confidence gained through independent confirmations by different instruments: “We observed at different times...That gives us a lot of assurance that these aren’t phantoms in the data.”
These findings represent some of the smallest planets detected using this method and signal potential for future discoveries across the universe. Jacob Bean reflected on this breakthrough: “It was like suddenly we know something that no one else does about the universe.”
Additional contributors from UChicago included postdoctoral fellows Rafael Luque, Lily L. Zhao, Tanya Das, David Kasper; graduate student Madison Brady; postbaccalaureate student Nina Brown; and masters student Rohan Gupta.
Funding for this research came from several sources including David and Lucile Packard Foundation, Heising-Simons Foundation, Gordon and Betty Moore Foundation, Gemini Observatory/National Science Foundation/NOIRLab/NSF/AURA/R.Proctor/J.Pollard