NASA and Princeton University scientists detected 1,284 planets outside Earth’s solar system using the space agency’s Kepler spacecraft. According to NASA’s chief scientist Ellen Stofan, this gives hope that finding another planet that sustains life like Earth is possible.

Kepler detected about 26 planets in the Goldilocks zone or the habitable zone. Of the nearly 1,300 newly discovered planets, 550 of these could possibly be rocky planets like Earth. The findings have been published in The Astrophysical Journal on May 10.

The announcement on Tuesday is the largest announcement of newly found planets so far, increasing the planets discovered by Kepler to more than 2,300. The research team analysed over 7,000 signals and confirmed with 99 percent certainty that 1,284 of those are due to planets orbiting in front of a star, which caused subtle dimming.

solar system

An artist’s conception of an exoplanet. Credit: NASA/Ames/JPL-Caltech.

According to Joshua Winn, an associate professor of physics at the Massachusetts Institute of Technology (MIT) and a former member of the Kepler team, confirming an individual signal in the solar system is not that easy. More often than not, these signals detected could just be another cosmic object aside from a planet.

In fact, Kepler has also identified 428 candidates as likely false positives. This means that the signals were not generated by a planet but by another object such as two stars orbiting each other, which resembles the signal of a transiting planet.

Moreover, if the planet candidate is as big as the planet Jupiter, it is highly unlikely to be another planet. Apparently, planets the size of Jupiter are extremely rare. When Kepler detected potential planet candidates with three to four times the size of Jupiter, the scientists concluded that these were not planets. Instead, they verified it was just double-star systems where one star passes in front of another star.

“It’s easier to mimic something the size of Jupiter, and we know Jupiter-sized planets are less common,” says lead author Timothy Morton, an associate research scholar of astrophysical sciences at Princeton University. “So the likelihood of a Jupiter-sized candidate actually being a planet that large is typically relatively low.”