Kepler-452b. Remember the name.
It might sound like a small, fiddly part that a plumber is going to have to pick up to fix your washing machine (arrival time, four to six years), but Kepler-452b is currently the closest thing we've got to "Earth 2.0".
Revealed at a press conference discussing the latest discoveries of the Kepler mission (which you can read up about here), Kepler-452b is the first near-Earth-sized exoplanet (a planet that sits within a solar system other than our own) that NASA has discovered sitting in a habitable zone - an orbital sweet spot that isn't too hot, nor to cold, but just right for forming liquid water, and thus holding the potential for supporting life.
"On the 20th anniversary year of the discovery that proved other suns host planets, the Kepler exoplanet explorer has discovered a planet and star which most closely resemble the Earth and our Sun," said John Grunsfeld, associate administrator of NASA’s Science Mission Directorate. "This exciting result brings us one step closer to finding an Earth 2.0."
There are some significant differences between Earth and its "cousin" 452b: its diameter is roughly 60 percent larger, it has a 385-day orbit and it's five percent further away from its parent star, Kepler-452. With an age of around 6 billion years, this star is 10 percent bigger, 20 percent brighter and much older than our own sun - by approximately 1.5 billion years.
The aspect of all these formidable numbers that's getting NASA most excited is that 452b has been spinning around a habitable zone for a much longer period of time than we have on Earth: this newly discovered planet has had 6 billion years of life-forming potential, while Earth has held the potential for life for 3.5 billion years. This means that not only could 452b have a head start on forming life, it could also hold clues as to how our own planet will behave as it ages.
"It’s awe-inspiring to consider that this planet has spent 6 billion years in the habitable zone of its star; longer than Earth. That’s substantial opportunity for life to arise, should all the necessary ingredients and conditions for life exist on this planet," said Jon Jenkins, Kepler Data Analysis Lead at NASA's Ames Research Center, who led the team that discovered Kepler-452b.
It's a huge discovery - but don't get excited about missions to Earth's cousin within our lifetime. The Kepler-452 system is located 1,400 light-years away in the constellation Cygnus, so we'll need to make some huge leaps in interstellar travel if we stand a chance of sending a probe to have a nose around.
NASA also revealed that its Kepler mission has discovered a further 521 exoplanet candidates, with 12 of these planets having diameters between one to two times that of Earth, and sitting in their star's habitable zone. As further analysis is conducted on the discoveries, Earth could soon find itself with a growing list of distant relatives.
You never know, one of them could call us for a family reunion any day now.