Scientists say the recent discovery of a distant exoplanet similar enough to Earth to be deemed a "cousin" could yield clues to how our Earth — and any planet possibly hospitable to life — might form.
Kepler 452b, a planet 1,400 light years distant, has a diameter around 1.63 times that of Earth, orbits a star very much like our sun every 384 days and, most importantly, sits in that star's habitable zone where liquid water could exist on the planet's surface, they say.
All those facts — a star very much like our sun, a planetary orbit just five percent longer than our yearly voyage around our sun only a little farther away and the planet's "earth-and-a-half" size — have astronomers excited.
"We can think of Kepler-452b as an older, bigger cousin to Earth, providing an opportunity to understand and reflect upon Earth's evolving environment," says Jon Jenkins at NASA's Ames Research Center in Moffett Field, California, leader of the group that discovered the exoplanet.
Astronomers believe Kepler 452b has spent its entire existence in its star's habitable zone of its star, and is likely to remain there for another three billion years.
Thought to be older than the Earth, that suggests that if — a big if — life exists there, it has had more time to evolve than has life on Earth.
"It's awe-inspiring to consider that this planet has spent 6 billion years in the habitable zone of its star; longer than Earth," Jenkins says. "That's substantial opportunity for life to arise, should all the necessary ingredients and conditions for life exist on this planet."
The astronomers note that the planet has not been observed directly — detected only by the dimming of its host star as it passes in front of it — and while much can be learned from such "transit" observations, like its orbit size and duration and its approximate size, much is still unknown about Kepler 452b.
It's not known if it's a rocky planet like Earth or a gas ball like Neptune, whether there is any liquid water on its surface or a surrounding atmosphere — in other words, things that would be needed for life to evolve are, at this point, just possible assumptions.
The discovery of Kepler 452b brings the total number of candidate planets discovered by the Kepler Space Telescope to 4,696.
That's an impressive total given that the first planet orbiting a sun-like star outside our solar system was discovered only 20 years ago.
"This is a great time we live in," says astronomer Didier Queloz, who, along with colleague Michel Mayor at the University of Geneva, discovered that first exoplanet around the star 51 Pegasi two decades ago.
Queloz says he believes it's not being overly optimistic to predict that, sometime in the near future, "the issue of life on another planet will be resolved."
