"The latest Kepler catalog of planet candidates was created using the most sophisticated analyses yet, yielding the most complete and reliable accounting of distant worlds to date".
Kepler scientist Mario Perez says that means that "we are probably not alone" because four years of data show how common Earth-like planets can be.
"Understanding their frequency in the galaxy will help inform the design of future Nasa missions to directly image another Earth". "This survey will enable new lines of research in exoplanet study, which looks at planets outside our solar system", said the release from NASA about Monday's announcement.
Around 50 of the planets are a similar size to Earth and are in the so-called "Goldilocks zone" - a distance from their star that is not too hot and not too cold for water to present.
"This carefully-measured catalog is the foundation for directly answering one of astronomy's most compelling questions - how many planets like our Earth are in the galaxy?" said Susan Thompson, Kepler research scientist for the SETI Institute.
Theresa May to 'reflect' after losing majority in Parliament
It was marked by a proposal to force elderly people to pay more for their care and her decision to skip a televised debate. It's all their Christmases rolled into one and they will make sure they leverage as much as they can from their advantage.
Ten of the planets are potentially rocky, close to the size of Earth and within the habitable zone of the stars they orbit - meaning they could support liquid water on their surface. A total of 2,335 of those have been verified as exoplanets, 21 of which are Earth-sized and orbit in their star's habitable zone.
The latest batch of over 200 planets can be separated into two distinct groups - Earth-size planets and gaseous planets smaller than Neptune. "Both results have significant implications for the search for life", NASA reports.
"There are now 4,034 planet candidates identified by Kepler", NASA said in a press statement.
"They say not to count our chickens before they're hatched, but that's exactly what these results allow us to do based on probabilities that each egg (candidate) will hatch into a chick (bona fide planet)". This data will enable scientists to determine what planetary populations - from rocky bodies the size of Earth, to gas giants the size of Jupiter - make up the galaxy's planetary demographics.
With the final catalog of planetary candidates from Kepler's original mission released, NASA will now focus on the "K2" mission, which began in 2014. As it trailed behind Earth's on its yearly trip around the sun, Kepler constantly watched more than 160,000 stars for any hint of dimming. Astronomers were at a loss to explain how such planets formed and whether there was a continuum between rocky terrestrial "super-Earths" and gassy "mini-Neptunes". The space administration's James Webb Space Telescope will launch in 2018, which will be able to "detect the chemical fingerprints of water, methane, oxygen, ozone, and other components of a planet's atmosphere".