“Similar to dawn or dusk on a spring day,” is how Geoff Marcey, an astronomer at the University of California, Berkeley, described Kepler-186f, the most Earth-like planet that hunters and their telescopes have yet turned up.
The description is certainly intriguing. Kepler-186f — so named because it was discovered by NASA’s orbiting Kepler telescope — just might be habitable. It’s exists in the “Goldilocks” zone, an area that’s neither too hot nor too cold for life — or at least life as we know it. Scientists say it could very well have water on its surface, and because its proximity to its sun puts it in a temperature zone, water would neither boil away nor freeze solid. Kepler-186f is also the closest in size to Earth of any known planet in a habitable region.
Trouble is — there always seems to be a “but” when it comes to newly discovered planets — Kepler-186f is in the constellation Cygnus, some 500 light years away. If you’re plotting your itinerary, a single light year approaches 6 trillion miles. Forget about commuting.
Kepler-186f — the folks involved in planet hunting really need to come up with better names — is a little larger than Earth and, along with four other planets about its size, orbits a red dwarf star. A year on Kepler-186f lasts 130 days.
Distance isn’t the only problem for Earthlings who wonder how many more days we’ll enjoy on our home planet before we need to find another place to live. The atmosphere on Kepler-186f — if it has one — is probably loaded with carbon dioxide. That probability prompted Lisa Kaltenegger, an astronomer at Harvard and the Max Planck Institute, to warn, “Don’t take off your breathing mask if you ever land there.”
Kepler — the telescope, not the planet — has been quite a planet finder. It has confirmed the existence of 961 planets since it was launched four years ago. Most of them, however are hostile in the extreme, and some are giant balls of gas. Only about a dozen of all those planets are considered even potentially habitable.
Unfortunately, we may never find out whether we could survive on Kepler-186f. It’s too distant for any space telescope humans have invented or any on the drawing board to study in enough detail to provide clues to its habitability.
Meanwhile, space hunters will keep looking. Who knows, maybe this very minute, someone or something on a distant planet is celebrating the discovery of Earth and wondering whether it’s habitable.