A haul of planets from Nasa's Kepler telescope includes a world sharing many characteristics with Earth.
Kepler-452b orbits at a very similar distance from its star, though its radius is 60% larger.
Nasa scientists said they believe it is the most Earth-like planet yet.
Such worlds are of interest to astronomers because they might be small and cool enough to host liquid water on their surface - and might therefore be hospitable to life.
Nasa's science chief John Grunsfeld called the new world the "closest so far" to Earth.
"It's a real privilege to deliver this news to you today," said John Jenkins, Kepler data analysis lead at Nasa's Ames Research Center in California.
"There's a new kid on the block that's just moved in next door."
The new world joins other exoplanets such as Kepler 186f with characteristics like Earth's.
Determining which is most Earth-like depends on the characteristics one considers. Kepler 186f, announced in 2014, is smaller than the new planet, but orbits a red dwarf star that is significantly cooler than our own.
Kepler 452b, however, orbits a parent star which belongs to the same class as the Sun; it is just 4% more massive and 10% brighter. Kepler 452b takes 385 days to complete a full circuit of its star, so its orbital period is 5% longer than Earth's
The mass of Kepler 452b cannot be measured yet, so astronomers have to rely on models to estimate a range of possible masses, with the most likely being five times that of Earth. If it is rocky, the world would likely still have active volcanism and its gravity would be roughly twice that on our own planet.

Scientists looking at data from the Kepler observatory have announced the discovery of 500 new possible planets around distant stars.
Twelve of the new candidates are less than twice Earth's diameter, orbiting in the so-called habitable zone around their star.
This zone refers to a range of distances at which the energy radiated by the star would permit water to exist as a liquid on the planet's surface.
Of these candidates, Kepler 452b is the first to be confirmed as a planet.
Dr Suzanne Aigrain, from the University of Oxford, who was not involved with the study, told BBC News: "I do believe the properties described for Kepler 452b are the most Earth-like I've come across for a confirmed planet to date."
"What seems even more significant to me is the number of planets in the habitable zone of their host stars with radii below two Earth radii; 12 is quite a few compared to the pre-existing Kepler planet catalogue.
"It bodes well for their attempts to provide a more robust measure of the incidence of Earth-like planets, which is the top-level goal of the Kepler mission."

The internet has suddenly lit up over news that Nasa may be about to announce a huge discovery. Here we go through what you need to know.
Nasa will unveil the discovery of a new planet reportedly similar in atmosphere and substance to that of Earth – i.e. capable of supporting life.
Why are people talking about something called Kepler?
The Kepler Telescope, launched by Nasa in 2009, has one purpose: to find Earth-like planets orbiting other stars. If Nasa has found a new Earth, this is the mission that will have discovered it.
It surveys portions of the planet's Milky Way, monitoring the brightness of aproximately 145,000 sequence stars. The observatory beams the images back to scientists in Nasa who then examine the images to see if the brightness has dimmed as exoplanets cross in front of the stars. Costing a relatively cheap (for space missions) $400 million, Kepler is part of Nasa Discovery programme.
So far, the telescope has found 1,000 alien planets – but none that come nearly close enough to the conditions found on our own planet.
When will we find out?
The space agency is live streaming a conference from 5pm where scientists, will announce their findings to the world. You can watch the live stream here, as well as follow our live coverage here.
Why is this a big deal?
"Exoplanets, especially small Earth-size worlds, belonged within the realm of science fiction just 21 years ago," a Nasa statement said, doing nothing to calm the semi-feverish wonderings on much of the internet.
"Today, and thousands of discoveries later, astronomers are on the cusp of finding something people have dreamed about for thousands of years – another Earth."
Space watchers are speculating that because Nasa is holding a live press conference – rather than just releasing the data in a press release or report – they may have made their most significant discovery to date.

Spetulhu wrote:
Now start planning some way to get humans out there! I for one agree with Hawking - we have to spread out so we don't all go if something happens here.

Kepler-452b is smallest planet to date discovered orbiting in the habitable zone of a G2-type star, like our own
The planet is 60 per cent larger in diameter than Earth and is 1,400 light years away in the constellation Cygnus
It has the a similar size orbit to Earth, receives the same amount of sun light and has the same length of year
Scientists are not yet sure whether it hosts life, but say if plants were transferred there, they are likely to survive

 Soladrin wrote:

Spetulhu wrote:
Now start planning some way to get humans out there! I for one agree with Hawking - we have to spread out so we don't all go if something happens here.

Yes, spread the human plague, we must infect the entire universe!

 Alpharius wrote:

 Soladrin wrote:

Spetulhu wrote:
Now start planning some way to get humans out there! I for one agree with Hawking - we have to spread out so we don't all go if something happens here.

Yes, spread the human plague, we must infect the entire universe!

Such cynicism and self-loathing!

Why so...sad?

 Soladrin wrote:

Spetulhu wrote:
Now start planning some way to get humans out there! I for one agree with Hawking - we have to spread out so we don't all go if something happens here.

Yes, spread the human plague, we must infect the entire universe!

 KingCracker wrote:

 Soladrin wrote:

Spetulhu wrote:
Now start planning some way to get humans out there! I for one agree with Hawking - we have to spread out so we don't all go if something happens here.

Yes, spread the human plague, we must infect the entire universe!

OK agent Smith

 KingCracker wrote:

 Soladrin wrote:

Spetulhu wrote:
Now start planning some way to get humans out there! I for one agree with Hawking - we have to spread out so we don't all go if something happens here.

Yes, spread the human plague, we must infect the entire universe!

OK agent Smith