(CNN)The Kepler mission has discovered 1,284 planets, the most exoplanets announced at one time, according to Princeton associate research scholar Timothy Morton during a NASA press conference. This more than doubles the number of previously confirmed planets from Kepler.
NASA's record-breaking planet discovery 00:47
"Kepler is the first telescope for detecting small rocky planets in the habitable zone of their stars," said Paul Hertz, Astrophysics Division director at NASA. "Thanks to Kepler, we know exoplanets are common, most stars in our galaxy have planetary systems and they are potentially habitable planets. Knowing this is the first step to addressing whether are we alone in the universe."
Since launching in 2009, Kepler has been watching more than 150,000 stars in one part of the sky to determine exoplanet candidates, based on the slight dimming of stars as potential planets pass across them.
Exoplanets in the hall of fame.
The goal has been to discover more Earth-like planets, or goldilocks, in the habitable zone, where water can pool on the surface of a planet. They are usually 1.6 times the size of Earth with rocky terrain. Of these newly discovered planets, nine orbit in the habitable zone of their star and nearly 550 are possibly rocky planets roughly around the same size as Earth. The discovery of these nine planets contributes to 21 exoplanets in the habitable zone "hall of fame."
To verify whether a candidate could be confirmed as a planet, scientists used a time-consuming, in-depth process analyzing each one, often using ground-based telescopes or radial velocity to determine mass. This also required resource-intensive follow-up observation. Candidates are prone to creating astrophysical false positives, or imposter scenarios, creating hope for a planet when it was actually something else.
Morton discovered he could use Kepler's current catalog of planets and statistical analysis to assign a planet-hood probability percentage to each candidate found by Kepler. This way, scientists could determine a way to quantify the probability that a signal is in fact a planet without follow-up observation.
The portion of sky Kepler has studied.
The simulations create detailed shapes of transit signals attributed to planets and imposters and how common imposters are in the Milky Way galaxy. Combining the two simulations provides a reliability score between 0 and 1. Anything greater than 99% is a "validated planet."
Compared with previous techniques, this is fully automated and can be applied to all candidates at once, only taking a few minutes per candidate to do the calculation.
Planet candidates in blue, found with previous methods, versus the candidates found with the new method, in orange.
"Planet candidates can be thought of like bread crumbs," said Morton. "If you drop a few large crumbs on the floor, you can pick them up one by one. But, if you spill a whole bag of tiny crumbs, you're going to need a broom. This statistical analysis is our broom."
The current Kepler catalog included 4,302 potential planets. In addition to the 1,284 confirmed planets, 1,327 are most likely planets but require further study and 707 are potential imposters. This analysis also validated 984 candidates previously verified using ground telescopes or other methods.
"When Kepler first started, we thought false positives were really common," Morton said. "I came to studying this problem with a fresh perspective and clear vision. By applying a new method, we've created a paradigm shift."
Photos: Where life might live beyond Earth
Photos: Where life might live beyond Earth
The Kepler mission has discovered 1,284 new planets. Of these newly discovered planets, nine orbit in the habitable zone of their star and nearly 550 are possibly rocky planets roughly around the same size as Earth.
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Photos: Where life might live beyond Earth
This artist's impression shows an imagined view from the surface one of the three planets orbiting an ultracool dwarf star just 40 light-years from Earth that were discovered using the TRAPPIST telescope at ESO's La Silla Observatory. Given the proximity of the dwarf star, the rosy sun would appear very large in the sky.
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Photos: Where life might live beyond Earth
On Thursday, July 23, NASA announced the discovery of Kepler-452b, "Earth's bigger, older cousin." This artistic concept shows what the planet might look like. Scientists can't tell yet whether Kepler-452b has oceans and continents like Earth.
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Photos: Where life might live beyond Earth
Kepler-452b is about 60% larger than Earth, left. It's about 1,400 light-years from Earth in the constellation Cygnus.
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Photos: Where life might live beyond Earth
A team of astronomers announced April 17, 2014, that they discovered the first Earth-size planet orbiting a star in the "habitable zone": the distance from a star where liquid water might pool on the surface. That doesn't mean this planet has life on it, says Thomas Barclay, a scientist at the Bay Area Environmental Research Institute at Ames and a co-author of a paper on the planet, called Kepler-186f. He says the planet can be thought of as an "Earth-cousin rather than an Earth-twin. It has many properties that resemble Earth." The planet was discovered by NASA's Kepler Space Telescope. It's about 500 light-years from Earth in the constellation Cygnus. The picture above is an artist's concept of what it might look like.
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Photos: Where life might live beyond Earth
Scientists announced in June 2013 that three planets orbiting star Gliese 667C could be habitable. This is an artist's impression of the view from one of those planets, looking toward the parent star in the center. The other two stars in the system are visible to the right.
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Photos: Where life might live beyond Earth
This diagram shows the planets thought to orbit star Gliese 667C, where c, f and e appear to be capable of having liquid water. The relative sizes, but not relative separations, are shown to scale.
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Photos: Where life might live beyond Earth
This diagram lines up planets recently discovered by Kepler in terms of their sizes, compared with Earth. Kepler-22b was announced in December 2011; the three Super-Earths were announced April 18, 2013. All of them could potentially host life, but we do not know anything definitive about their compositions or atmosphere.
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Photos: Where life might live beyond Earth
This illustration depicts Kepler-62e, a planet in the habitable zone of a star smaller and cooler than the sun. It is about 1,200 light-years from Earth in the constellation Lyra.
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Photos: Where life might live beyond Earth
This illustration depicts Kepler-62f, a planet in the habitable zone of a star smaller and cooler than the sun, in the same system as Kepler-62e.
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Photos: Where life might live beyond Earth
This diagram compares the planets of our own inner solar system to Kepler-62, a five-planet system about 1,200 light-years from Earth. Kepler-62e and Kepler-62f are thought capable of hosting life.
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Photos: Where life might live beyond Earth
The planet Kepler-69c is about 2,700 light-years from Earth in the constellation Cygnus.
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Photos: Where life might live beyond Earth
This diagram compares the planets of our own inner solar system to Kepler-69, which hosts a planet Kepler-69c that appears to be capable of hosting life, in addition to planet Kepler-69b.
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Photos: Where life might live beyond Earth
This artist's illustration represents the variety of planets being detected by NASA's Kepler spacecraft.
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The Kepler mission will end in October 2017. The team has until then to produce a final discovery catalog and quantify scaling for identifying exoplanets, as well as leaving data measurements for the scientific community as a way to pass the baton on to future missions, said Natalie Batalha, Kepler mission scientist.
These other missions -- like TESS, the Transiting Exoplanet Survey Satellite, in 2017 and the James Webb Space Telescope in 2018 -- will continue the search for life beyond Earth.
Compared to Kepler, TESS will use a similar transit method for observing planets, when they pass in front of their parent stars. While Kepler looked at one portion of the sky for stars that were further away for a longer time, TESS will observe the entire sky and focus on the brightest and closest stars, each for 30 days.
Current and future missions.
The James Webb Space Telescope is capable of observing large exoplanets and detecting starlight filtered through their atmosphere, which will enable scientists to determine the atmospheric composition and analyze them for gases that can create a biological ecosystem.
The K2 mission, which launched in 2014, is extending Kepler's legacy to new parts of the sky and new fields of study, adding to NASA's "arc of discovery." It has enough fuel to keep identifying candidates until summer 2018. It is helping bridge the gap between Kepler and TESS as far as identifying targets for the James Webb Space Telescope to observe.
So, just how many exoplanets do we estimate are out there in the galaxy for NASA to study and discover? Tens of billions of Earth-sized habitable planets, Batalha said. In the future, NASA wants to increase its understanding from the habitable zone to habitable environments and living worlds.
"With this discovery, we're going to change the way we see the universe," Batalha said. "You'll look up at the sky and see pinpoints of light and think of them as planetary systems, not just stars. We're going to know how life manifests itself in the galaxy."
