Of the more than 5,000 exoplanets now in astronomers’ catalogs, the most intriguing yet might be one confirmed last week, a potentially habitable world of fire and ice twirling around a nearby sunlike star.
Dubbed HD 20794 d (because HD 20794 is the name of its star and it is accompanied by two previously announced planetary siblings, HD 20794 b and HD 20794 c), this planet is at least as massive as 6.5 Earths. This could make it a relatively Earth-like world of mostly rock with a thin atmosphere—a so-called super-Earth—although it could instead be more of a mini-Neptune with thick layers of gas or a deep global ocean surmounting a solid core. Besides its uncertain nature, HD 20794 d’s most “intriguing” aspect is its distinctly noncircular 647-day orbit, which at one end reaches frigidly farther out from its star than Mars does from the sun and, at its other end, is as scorchingly close as Venus. This eccentric orbital path traverses the star’s habitable zone, the region in which liquid water might persist and allow life to arise, although the planet’s cycles of hot and cold could at turns boil water into steam or freeze it as ice.
And this strange new world is tantalizingly close: At scarcely 20 light-years from Earth, it’s within reach of deeper, more direct scrutiny by future space telescopes, beckoning astronomers to look closer. Someday, in order to pin down its true planetary form, researchers could scour snapshots of the world to look for evidence of a volatile climate from its peculiar orbit and clarify whether it’s actually habitable—or even inhabited.
To read more, click here.