A red dwarf star that was previously thought to be the source of a weird signal from aliens turns out to have a temperate Earth-sized planet, astronomers reported today.
The “Weird! Signal,” detected this summer, turned out to be nothing more than earthly interference. In contrast, the planet known Ross 128 b is very real, and it’s only 11 light-years away.
That makes it the second-closest exoplanet thought to have temperate conditions. What’s more, the planet orbits a star that’s less active than the closer-in planet, Proxima Centauri b, which could make Ross 128 b a better bet for life’s presence.
Proxima b, which is a mere 4.2 light-years away, also circles a red dwarf star, within a habitable zone where water could exist in liquid form.
However, stars like Proxima Centauri periodically erupt in flares that would bathe any close-in planets in potentially deadly ultraviolet and X-ray radiation. That’s why astrobiologists are uncertain about the prospects for life on Proxima b.
In contrast, the newfound planet’s parent star, Ross 128 in the constellation Virgo, is an inactive red dwarf. Theoretically, organisms on that planet would be dealing with a much quieter radiation environment than that found on Proxima b.
Ross 128 b was detected using the European Southern Observatory’s High Accuracy Radial Velocity Planet Searcher, or HARPS, at the La Silla Observatory in Chile.
“This discovery is based on more than a decade of HARPS intensive monitoring, together with state-of-the-art data reduction and analysis techniques,” Geneva Observatory astronomer Nicola Astudillo-Defru said in a news release. Astudillo-Defru is one of the authors of a paper on the discovery in the journal Astronomy & Astrophysics.
The planet orbits its parent star once every 9.9 days, at a distance of roughly 19 million miles. The astronomers estimate that Ross 128 b should receive about 38 percent more irradiation than Earth, resulting in an equilibrium temperature somewhere between 68 degrees and minus-76 degrees Fahrenheit.
It’s not yet clear whether the planet is officially within Ross 128’s habitable zone, the research team said. Depending on the computer modeling, the planet could be inside, outside or just on the edge of the orbital area where liquid water could exist.
Despite the uncertainty, a planet that’s 11 light-years away, either having liquid water or just shy of having some, would make for “an extremely appealing characterization target,” the researchers say.
For that reason, the European Southern Observatory said Ross 128 b will be a “prime target” for the Extremely Large Telescope, which is currently under construction and should be able to search for biomarkers in the planet’s atmosphere.
In addition to Astudillo-Defru, the authors of “A Temperate Exo-Earth Around a Quiet M Dwarf at 3.4 Parsecs” include Xavier Bonfils, R. Díaz, J.-M. Almenara, T. Forveille, F. Bouchy, X. Delfosse, C. Lovis, M. Mayor, F. Murgas, F. Pepe, N. C. Santos, D. Ségransan, S. Udry and A. Wünsche.