Heavens! It turns out Earth has a distant cousin
Scientists find ‘Kepler-186f’ existing 500 light-years away, call it most-similar planet yet
LOS ANGELES— Astronomers have discovered what they say is the most Earth-like planet yet detected — a distant, rocky world that’s similar in size to our planet and exists in the Goldilocks zone where it’s not too hot and not too cold for life.
The find, announced Thursday, excited planet hunters who have been scouring the Milky Way Galaxy for years for potentially habitable spots outside our solar system.
“This is the best case for a habitable planet yet found. The results are absolutely rock solid,” University of California, Berkeley, astronomer Geoff Marcy said in an email. Marcy had no role in the discovery.
The planet was detected by NASA’s orbiting Kepler telescope, which examines the heavens for subtle changes in brightness that indicate an or- biting planet is crossing in front of a star. From those changes, scientists can calculate a planet’s size and make certain inferences about its makeup. The new-found object, dubbed Kepler-186f, circles a red dwarf star 500 light-years from Earth in the constellation Cygnus. A light-year is almost 9.5 trillion kilometres. The planet is about 10 per cent larger than Earth and may very well have liquid water — a key ingredient for life — on its surface, scientists said. That is because it resides at the outer edge of the habitable temperature zone around its star — the sweet spot where lakes, rivers or oceans may exist without freezing solid or boiling away.
The planet probably basks in an orange-red glow from its star and is most likely cooler than Earth, with an average temperature slightly above freezing, Marcy said.
The discovery was detailed in Friday’s issue of the journal Science.
Lead researcher Elisa Quintana said she considers the planet to be more of an “Earth cousin” than a twin because it circles a star that is smaller and dimmer than our sun. While Earth revolves around the sun in 365 days, this planet completes an orbit of its star every 130 days.
Scientists cannot say for certain whether it has an atmosphere, but if it does, it probably contains a lot of carbon dioxide, outside experts said.
Despite the differences, “now we can point to a star and know that there really is a planet very similar to the Earth, at least in size and temperature,” Harvard scientist David Charbonneau, who was not part of the team, said in an email.
Since its launch in 2009, Kepler has confirmed 961planets, but only a few dozen are in the habitable zone.