On Wednesday, a team of European scientists announced the discovery of an Earth-size exoplanet orbiting a star just 11 light-years away. In reporting their findings in the journal Astronomy & Astrophysics, the scientists added yet another option to the blossoming list of “planets outside the solar system that could be potentially habitable to life,” with this latest world being touted as one of the best chances—possibly the best chance—for finding extraterrestrial life yet.
Why is it so promising? In part because the new planet, called Ross 128 b, orbits what seems to be an inactive red dwarf star. These specific circumstances give it better odds for sustaining a more stable environment amenable to life.
The hype surrounding Ross 128 b may also be due to its similarity to another exoplanet, Proxima b, which orbits red dwarf Proxima Centauri a mere 4 light-years away. Proxima b’s discovery made an incredibly loud splash in the world of astronomy and astrobiology. Not only was it the closest exoplanet ever found, but it was sitting in the habitable zone of its host star—the region around a star where scientists believe the conditions are opportune for a rocky planet to sustain liquid water on its surface. And of course, where there’s water, there’s the potential for life.
The problem, unfortunately, was that the relationship between Proxima Centauri and Proxima b wasn’t the most serene. As astronomers paid more attention, they began realizing that Proxima Centauri, like many red dwarfs, was probably incredibly active in its youth, spewing intense amounts of stellar radiation that would have almost certainly bludgeoned the small planet. Proxima b hugs its star tightly, and that close orbit means that radiation might have been enough to strip it of any atmosphere it may have developed. That’s obviously bad news for the survivability of life.
Meanwhile, Ross 128, the host star of Ross 128 b, is an exceptionally quiet star. Even though the planet is 20 times closer to its star than Earth is to the sun (the orbit is just 9.9 days), chances are much better Ross 128 b is temperate, particularly when compared with Proxima b. The research team estimates that Ross 128 b receives just 38 percent more radiation than Earth does and should have equilibrium temperatures between minus 76 degrees Fahrenheit and 69 degrees Fahrenheit. That’s a big range, sure, but on either extreme it’s still within the realm in which life can exist.
Moreover, although the star system is 11 light-years away right now, it’s actually moving toward our solar system. In just 79,000 years, Ross 128 b will be closer to us than Proxima b. (We’ll all obviously personally be dead by then, but maybe life will still exist on Earth?)
Still, while Ross 128 b is a fascinating discovery, it’s way too early to say anything definitive about its potential. The new findings have plenty of shortcomings of their own. For one, the European Southern Observatory team has no idea yet whether the new exoplanet sits in Ross 128’s habitable zone. As with every other exoplanet we like to call “potentially habitable,” there’s no indication whether the planet has water on its surface. There isn’t even any sign as to whether the planet possesses other elements essential to life as we know it, like atmospheric oxygen. So unfortunately, it would be a stretch to label Ross 128 b as “potentially habitable.”
Also, the discovery was made using the ESO’s planet-hunting High Accuracy Radial Velocity Planet Searcher instrument in Chile, but it hasn’t been observed with any other instrument yet. No observation in science is worth taking seriously if it can’t be verified or replicated.
Some of these questions could be resolved relatively soon. The ESO’s Extremely Large Telescope could find out whether Ross 128 b possesses oxygen or other chemical markers that could be signs of habitability or extant life. But others, such as the presence of water, are going to require more advanced instruments that we have yet to develop. Maybe we’ll have them by the time the planet gets closer.