Small Rocky Planet Discovered Orbiting Nearby Barnard’s Star, According to Reuters

By Will Dunham

WASHINGTON (Reuters) – Barnard’s star is classified as a red dwarf, the smallest category of regular stars, significantly smaller and less luminous than our sun. Located approximately 6 light years away, it is the closest single star—one that does not orbit with other stars—to our solar system and is considered a nearby celestial object in the vast cosmos.

This proximity has excited scientists who are interested in exploring nearby potentially habitable worlds, particularly following the confirmation of the first planet orbiting Barnard’s star. This planet has a rocky structure and a mass roughly 40% that of Earth.

Although the confirmed planet, termed Barnard b, orbits very close to its star with a surface temperature that renders it inhospitable to life, researchers have detected "strong hints" of three additional planets around Barnard’s star that might offer better conditions for habitation.

Barnard b has an estimated diameter of about 6,000 miles (9,700 km), roughly three-quarters of Earth’s size. "It is one of the least massive planets ever discovered beyond our solar system," remarked astronomer Jonay González Hernández from the Instituto de Astrofísica de Canarias in Tenerife, Spain, who led the study published this week in the journal Astronomy & Astrophysics.

In comparison, only Mars and Mercury are smaller within our solar system. Barnard b has a scorching surface temperature of around 275 degrees Fahrenheit (125 degrees Celsius) and completes its orbit around Barnard’s star in merely three Earth days, at a distance approximately twenty times closer than Mercury is to the sun.

Planets outside the solar system are referred to as exoplanets. Researchers focused on identifying exoplanets that may support life particularly look at those in the "habitable zone" surrounding a star, where temperatures allow for liquid water to exist on the surface.

Utilizing an instrument named ESPRESSO on the European Southern Observatory’s Very Large Telescope in Chile, scientists made this discovery. The three potential planets in orbit around Barnard’s star appear to be rocky and smaller than Earth, with masses between 20-30% of that of our planet. There is hope that at least one of these may reside within the habitable zone.

If validated, Barnard’s star would become the only known star with a multi-planet system composed entirely of planets smaller than Earth.

Located in the constellation Ophiuchus, Barnard’s star has a mass equal to about 16% of the sun’s and a diameter around 19% of its size, as well as being considerably cooler. It is estimated to be more than twice the age of our sun.

"Due to its size and low temperature, it is quite faint, causing its habitable zone to be much closer to the star than it is for the sun," stated Alejandro Suárez Mascareño, an astronomer from the Instituto de Astrofísica de Canarias and co-author of the study. "Furthermore, it is a very quiet star; unlike some red dwarfs known for frequent flares, Barnard’s star remains stable."

Closer exoplanets are easier to study, and low-mass rocky planets around red dwarfs, the most common star type in the Milky Way galaxy, are more readily detectable than those around larger stars.

Barnard’s star is surpassed in proximity only by three stars in the Alpha Centauri system, which is about 4 light years away. A light-year is the distance light travels in one year, approximately 5.9 trillion miles (9.5 trillion km). The Alpha Centauri system has two detected exoplanets, both orbiting the red dwarf Proxima Centauri; one has a mass comparable to Earth’s, while the other is about 25% of Earth’s mass.

In works of science fiction, traveling at light speed is a common theme. However, in reality, such capabilities remain far beyond current human technology, though projects like Breakthrough Starshot are exploring the viability of interstellar travel. Both Barnard’s star and Alpha Centauri are likely to be high on the wish lists for future exploration.

"Despite their relative closeness in astronomical terms, they are still out of reach for any existing human technology. However, if initiatives like Breakthrough Starshot succeed, these could be among the first targets for exploration," noted Mascareño.