Scientists are now one step closer to answering whether life exists on other planets.
NASA released a list of 219 new “planet candidates” discovered by the Kepler space telescope, 10 of which are similar to Earth’s size and may be habitable by other life forms. The announcement Monday marks the end of Kepler’s search for planets orbiting other stars in the constellation Cygnus, bringing the telescope’s tally to 4,034 planet candidate discoveries.
Of those discoveries, scientists have verified 2,335 as planets. More than 30 of those confirmed planets are similar in size to Earth and in their star’s “habitable zone” ― the range of distance from a star where liquid water could pool ― while around 20 others that fit that description remain unverified, according to NASA.
Most of the planets they discovered are smaller than Neptune, which is about four times the diameter of Earth, Kepler research scientist Susan Thompson said at a press briefing Monday in Mountain View, California.
This survey catalog will be the foundation for directly answering one of astronomy’s most compelling questions: How many planets like our Earth are actually in the galaxy?
Susan Thompson, Kepler research scientist
Monday’s findings inch closer to solving one of humanity’s great cosmic mysteries, she said.
“This survey catalog will be the foundation for directly answering one of astronomy’s most compelling questions: How many planets like our Earth are actually in the galaxy?”
Beyond the additions to the Kepler catalog, scientists working on the mission revealed Monday that they’ve identified two distinct groupings of small planets, which range in size from Earth to Neptune.
About half are similar to Neptune in size and composition in that they have thick atmospheres and are mostly gas with “no surface to speak of,” Benjamin Fulton, a doctoral candidate who analyzed Kepler’s findings, said Monday. The other half are similar to Earth in size and are rocky with little to no atmosphere.
Discovering that distinction “sharpens up the dividing line between potentially habitable planets and those that are inhospitable to life as we know it,” Fulton explained, likening it to “the discovery that mammals and lizards are separate branches on the tree of life.”
It also revealed the likelihood that those rocky, potentially habitable planets are usually no bigger than 75 percent larger than Earth, he said.
Monday’s NASA announcement marks Kepler’s eighth release of data after a four-year mission and years of analyzing the findings. Since 2014, Kepler has been on a second mission to find more exoplanets in different areas of the cosmos.