Are we alone? 

It’s one of the most basic, and maddening, questions ever posed by scientists, but we’re now one step closer to answering it. 

A new set of data released by NASA’s Kepler mission catalogs 219 newfound alien planet candidates. According to NASA, 10 of the new worlds appear to be rocky in the habitable zones of their stars, meaning that they might support bodies of liquid water on their surfaces. 

This may not sound all that different from previous Kepler announcements showing off the spacecraft’s ability to find hundreds of new planets in our cosmic backyard, but this new dataset is special for another reason. 

The new set of planet candidates represents the final data from Kepler’s initial mission, which lasted from 2009 to 2013, and it is our best chance to finally figure out just how many possibly Earth-like planets orbiting sunlike stars our Milky Way contains. 

“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?” Susan Thompson, Kepler research scientist, said in a statement.

In total, Kepler has discovered about 50 possibly rocky worlds orbiting in the habitable zones of their stars out of thousands of exoplanet candidates discovered by the spacecraft to date.

Thanks to the new data, scientists finally have enough information to start the complicated statistical analysis that will be required to pin down exactly how unique we are in the context of the universe.

“There are a lot of pieces that go into it,” Thompson said during a press conference, referring to finding the number of Earth-like planets around sunlike stars. 

“But at least we now have all of those pieces. Scientists will spend the next year talking about how to get to the most accurate number and the best way to go about it.”

The planets discovered by Kepler were found thanks to the transit method, meaning that the spacecraft measured small dips in the light of a star caused by a planet passing in front of it from Earth’s perspective. 

Kepler’s initial mission was designed to stare deeply at one part of the sky and pick out the planets hiding within it, allowing scientists to statistically analyze how many possibly Earth-like worlds lurk out there in the Milky Way. 

In 2013, however, that mission came to an end due to a mechanical failure. 

Kepler is now unable to focus on one part of the sky to hunt for planets, so instead researchers are using the spacecraft to look at a variety of different parts of the sky, keeping an eye out for planets. 

Scientists are somewhat obsessed with finding other possibly Earth-like planets around our kind of star for a pretty obvious reason: Earth is the only planet we know of that can play host to life. 

If we find our planetary twin out there in the universe, then we might have found our next-best chance to figure out if we really are alone or just one of many. 



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