March 17, 20254 min readNewfound Exoplanets around Barnards Star Resolve Long-Standing Astronomical QuestFour small, newly discovered worlds are less than six light-years away from Earth, and their discovery reinforces a cautionary tale from planet huntings prehistoryBy Tom Metcalfe edited by Lee BillingsAn artists impression of four small, likely rocky exoplanets orbiting Barnards Star, a red dwarf star about six light-years away from Earth. International Gemini Observatory/NOIRLab/NSF/AURA/P. MarenfeldAstronomers have confirmed the existence of four small planets around Barnards Star, one of Earths nearest and perhaps most notorious neighboring stars.The new discoveries verify a study last year that suggested Barnards Star was orbited by at least one planet; the worlds were discovered using the radial velocity method, which can detect otherwise hidden exoplanets via a subtle wobble that their orbital tugging causes in motions of their host stars. The frequency of that stellar wobble reveals an exoplanets orbital period and distance from its star, and its strength provides an estimate of the unseen worlds mass.The observations indicate that each of the four planets around Barnards Star is much smaller than Earthbetween 20 percent and 30 percent of its mass. That means they are probably rocky, like the inner planets of our solar system. But they all orbit so closely to Barnards Star that they would be too hot for life as we know it.On supporting science journalismIf you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.Besides their close proximity to Earth, these worlds are also noteworthy for being among the smallest yet found via the radial velocity method. In recent years, the instruments have grown to give an unprecedented precision in radial velocities, says astrophysicist Ritvik Basant, a doctoral student at the University of Chicago and lead author of a study in the Astrophysical Journal Letters that confirms the exoplanets.The researchers are using the MAROON-X spectrograph on the Gemini North telescope in Hawaii to look for the radial velocity wobbles of exoplanets around nearby stars. We have been taking data for the last three years, Basant says.Discovered in 1916 by American astronomer Edward Emerson Barnard, Barnards Star is a small and slow-burning red dwarf classified by astronomers as an M-type star. It is about six light-years away but only has about 15 percent of the mass of our sun; this makes it very faint despite its nearness to our solar system, and it cannot be seen in the sky by the unaided eye.After its discovery, the next time Barnards Star made headlines was in 1963, when Dutch astronomer Peter van de Kamp declared hed found evidence that it was orbited by a planet with about 1.6 times the mass of Jupiter. No exoplanets had been confirmed at the time, so van de Kamps announcement was an important event. Van de Kamp had observed Barnards Star for more than a quarter century prior to his announcement, and he claimed hed seen a periodic perturbation in the stars motions that was caused by the orbiting planet. Subsequent studies showed that these signs of van de Kamps planet actually came from minor spatial shifts of components in his telescope caused by their occasional maintenance. The debunking cast a shadow over planet-hunting for generations, but van de Kamp nevertheless championed his discovery for many years until his death in 1995.The latest finds around Barnards Star have little to do with this earlier sagaother than reinforcing how this historic episode should be considered a cautionary tale. But they have set a new benchmark for the detection of small exoplanets around nearby stars, Basant says. The observations suggest that the planets orbit Barnards Star in a plane almost edge on to Earth. They dont pass directly in front of the star as seen from our planet, howeversuch transits would be useful for determining each worlds exact size and even details of its atmospheric composition. Still, Barnards Star is so close that it may be possible to take their pictures in a difficult process called direct imaging, which involves blotting out most of a stars light so that the far fainter light from any accompanying planets can be seen.The observations also indicate that all four planets orbit only a few million miles from Barnards Star much closer than the average 36-million-mile distance of Mercury from our sun. The nearest zips around completely in just two and a half Earth days at a distance of roughly 1.7 million miles, while the farthest orbits in less than seven days at a distance of about 3.5 million miles.Similar compact systems of small planets have been detected around many other red dwarf stars, which are the most common stars in the universe, says Rice University planetary scientist Andr Izidoro, who was not involved in the study. Izidoro and his Rice University colleague Sho Shibata have used exoplanet data from NASAs Kepler space telescope to create an updated model of planetary formation that may account for these smaller star systems. Their new model, which was also published recently in the Astrophysical Journal Letters, proposes that smaller planets mostly arise from impacts in rings of debris that from in whirling disks of gas and dust that surround nascent stars, while larger planets are usually born further out from a star, where the colder temperatures offer more abundant frozen material for world-building.In the case of Barnards Star, Izidoro says it is likely the four planets had formed farther away than they are now but migrated inward because of gravitational interactions with the protoplanetary disk from which they first emerged. It is still possible that other rocky planets may lurk undiscovered around Barnards Star in more distant orbits, he says, where conditions would be cooler and perhaps even suitable for life.