Barnard’s Star orbited by four tiny planets

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March 13, 2025
3 min read

Barnard’s Star orbited by four tiny planets

New evidence has found that there are as many as four tiny planets orbiting Barnard’s Star, the next nearest star system to Earth. The four worlds are each no more than 20-30% the mass of the Earth. They are so close to the star that they complete an orbit within days. This likely makes them too hot to be habitable.

The find however, sets a new benchmark for discovering smaller planets around nearby stars.

“It’s a really exciting find — Barnard’s Star is our cosmic neighbor, and yet we know so little about it,” said Ritvik Basant, Ph.D student at the University of Chicago and first author on the study. “It’s signaling a breakthrough with the precision of these new instruments from previous generations.”

This supports a November study from a team with a different telescope that found strong evidence for at least one planet around Barnard’s Star and hinted at others. For a century, Barnard’s Star had been studied by astronomers who had hoped to find planets orbiting it.

Discovered by E. E. Barnard at Yerkes Observatory in 1916, it is the closest star system that has the same configuration we do; only a single star. The nearest of all to us, Proxima Centaur, has three stars circling one another, changing the dynamics of planetary formation and orbits.

Barnard’s Star is of a type known as an M dwarf star, one that is very common in the universe. This is creating more curiosity among scientists who would like to learn more about the kinds of worlds that orbit them.

But because they are so far away, the planets are too small to be seen, especially next to the star itself. Astronomers therefore need to be more creative when searching for them. UChicago Prof. Jacob Bean led one such effort, attaching an instrument designed specifically to search for distant planets. Because of the size differences, they look for the effect the planets have on the star, including causing it to wobble due to gravity, and a slight dimming of its light.

The study included scientists with the Gemini Observatory/National Science Foundation NOIRLab, Heidelberg University, and the University of Amsterdam, and is published in The Astrophysical Journal Letters.

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