Another tantalizing planet has been found outside our Solar System: an Earth-sized world that’s our cosmic next-door neighbor — and it could be in just the right spot to host life.
Meet Ross 128 b, a newly discovered planet found orbiting around a small, faint star known as a red dwarf. The world, which is about one-and-a-half times the mass of Earth, may be in the star’s habitable zone, too. (That’s the spot where temperatures are just right, possibly allowing liquid water to pool on a planet’s surface.) Most exciting of all is that this planet is situated just 11 light-years away. That makes Ross 128 b the second closest potentially habitable exoplanet to Earth we know about after Proxima b, a rocky world that orbits around the nearest star to our Solar System, Proxima Centauri.
However, Proxima Centauri isn’t a very “life-friendly” star. Also a red dwarf, it’s considered an active star, meaning it frequently burps out intense, high-energy solar flares. In fact, most red dwarfs are prone to flaring, which is bad news in the search for alien life outside our Solar System. Flaring stars can blast nearby planets with lots of radiation, stripping away their atmospheres and making them uninhabitable. But Ross 128 b’s star doesn’t seem to flare much at all.
“The planet we found is around one of the quietest stars in the solar neighborhood,” Xavier Bonfils, an astronomer at the Institute of Planetology and Astrophysics in Grenoble, France and lead author of a study in Astronomy & Astrophysics detailing the planet’s discovery, tells The Verge. That makes this planetary system much more conducive to hosting any potential life.
Bonfils and his team spent about a decade monitoring this red dwarf, called Ross 128, before they figured out a planet was lurking around it. The researchers used the HARPS instrument on the European Southern Observatory’s La Silla Observatory in Chile to periodically observe the star’s minuscule wobbles. Orbiting planets, while tiny, can gravitationally tug on a star, causing the star to shake in its orbit. After taking 116 measurements with HARPS, the team was able to conclude that an Earth-sized planet was orbiting around the star.
Because the planet is so low-mass, the researchers are pretty sure that it’s rocky like Earth. And based on their wobble measurements, the researchers found that Ross 128 b is very close to its sun, in an orbit that takes just 10 Earth days to complete. That puts the planet about 20 times closer to its star than Earth is to the Sun. But this star is also 280 times less luminous than our Sun, so Ross 128 b only receives about 40 percent more light than Earth does. That means the planet may have a surface temperature similar to Earth. Depending on how much light it reflects back into space, this planet could have the right temperatures needed for liquid water.
All of that, combined with the fact that Ross 128 is such an inactive star, makes this planet a prime candidate in the search for extraterrestrial life. “We have found extremely interesting planets like the ones orbiting Proxima Centauri or TRAPPIST-1, however these stars do not present the best conditions for life,” Nicola Astudillo-Defru, an astronomer at the University of Geneva in Switzerland and another lead author on the study, wrote in an email to The Verge. “Hence, it is more likely [we’ll] find [signs of life] on Ross 128 b than any other star.”
Of course, there’s still a lot we don’t know about this planet. Sure, it seems to have a lot of good stats, but scientists still don’t know what the planet’s climate is like, and that could seriously impact its habitability. Bonfils says it’s possible that clouds accumulate on the side of the planet facing the star, which could reflect a lot of the star’s radiation out into space. If so, that could prevent the planet from overheating. However, the planet could also be particularly dark, causing it to absorb too much light and trigger a runway greenhouse effect.
We won’t know for sure what kind of atmosphere this planet has until we look at it directly, and that may not happen for a while. There aren’t really any telescopes available right now that can see Ross 128 b directly. “For now we will continue to monitor the star to search for additional companions,” wrote Astudillo-Defru.
But a new giant telescope is being built in Chile — aptly named the Extremely Large Telescope, or ELT — which could use to peer into this planet’s atmosphere. When it’s up and running sometime around 2025, the ELT may be powerful enough to directly image Earth-sized exoplanets and figure out what their atmospheres are made of. If the ELT can see into Ross 128 b’s atmosphere and find the critical gases associated with life — water vapor, oxygen, and methane — then scientists will have a better idea of whether life is present. “If we are able to identify all three [gases] in the same exoplanet atmosphere, it would be a smoking gun for life on the surface,” says Bonfils.