Planets, planets everywhere and here and there an Earth. Astronomers announced the discovery this week of a new, temperate Earth-sized planet only 11 light years away orbiting the star Ross 128 in the constellation Virgo. After Proxima b, the planet circling Proxima Centauri in the Alpha Centauri triple star system, it’s the closest, potentially life-friendly planet found.
Both Proxima Centauri and Ross 128 are red dwarf stars, which are some of the faintest and coolest stars in the universe. They outnumber all the other types of stars we see in the night sky. Matter of fact, not a single red dwarf is visible with the naked eye. They’re also fertile hunting ground for exoplanets. One way astronomers find a planet is by measuring how much it tugs on its host star. A tiny dwarf feels a much stronger — and more easily measurable — tug by an orbiting planet compared to a bigger star like our sun.
Despite their small mass and size (a typical red dwarf is only about 1½ times the size of Jupiter), they’re famous for spouting violent flares than can bathe any planets in deadly ultraviolet and X-ray radiation, rendering them less fit as place where life might evolve. Proxima Centauri fits in this category. But Ross 128 isn’t prone to such tantrums, so its planets may be the closest known to offer a comfortable abode for life. Ross 128 b will be a prime target for European Southern Observatory’s Extremely Large Telescope, which will be able to search for biomarkers like oxygen in the planet’s atmosphere.
A team working with ESO’s High Accuracy Radial velocity Planet Searcher (HARPS) at the La Silla Observatory in Chile found that Ross 128 b is about the size of the Earth and orbits its host sun every 9.9 days. Since that’s 20 times closer than Earth orbits the sun, you might think you could fry an egg on a hypothetical sidewalk there in a split second. But since we’re talking a cool red dwarf star, the planet receives only 1.38 times more heat and light. Scientists estimate the that Ross 128 b ranges in temperature from –76° to 68° F (–60° to 20° C). That puts it either very close to the habitable zone, where liquid water may pool on its surface.
Nothing stays put in this universe except maybe my neighbor’s yard light, so although Ross 128 is currently 11 light-years from Earth, the star is moving towards us and will become our nearest stellar neighbor around 81,000 A.D. Ross 128 b will be just 6.2 light years away, almost as if one Earth was trying to reach out to another.