Our Universe got a whole lot busier.
NASA's Kepler Space Telescope mission has just announced the discovery of 1,284 new exoplanets - nine of which are considered potentially habitable.
This is the most new planets announced at any one time, and almost doubles the number of confirmed exoplanets out there in the Universe, which makes it a pretty huge deal. The discoveries were made using a new technique that allows scientists to assess the likelihood that blips in the data really are planets, and aren't the result of other astronomical objects.
"This announcement more than doubles the number of confirmed planets from Kepler," said Ellen Stofan, chief scientist at NASA Headquarters. "This gives us hope that somewhere out there, around a star much like ours, we can eventually discover another Earth."
When Kepler looks for exoplanets, it looks at the light coming from distant stars. Any sign of that light dimming slightly before it gets to Kepler could be a result of a planet passing in front of its sun.
That's the best system we have so far, but it can also lead to a whole lot of false positives because planets aren't the only thing that can dim a star's light - for example, it could be a binary star system, a brown dwarf, or a low-mass star.
To confirm what's going on, in the past we've had to follow up on each of those candidate planet observations one at a time using ground-based telescopes, which is incredibly time-consuming and expensive. It's one of the reasons we were only able to confirm 984 exoplanets before this, despite seven years of the Kepler mission.
But the new validation technique assesses the probability that planet candidates really are planets en masse, without any follow-up required.
This new technique is that metaphorical broom. It works by calculating two things: first, how much the shape of a candidate planet's transit signal looks like a planet, statistically speaking; and secondly, how common false positives 'imposter candidates' are out there.
Putting this information together gives scientists a reliability score between zero and one for each planet candidate. And candidates with a reliability greater than 99 percent can now be called 'validated planets,' without having to perform any follow-up observations.
Morton cross-checked this new method with the data from ground-based follow-ups in the past and found that his predictions matched up almost perfectly with what telescopes had seen. "For every planet that the ground-based surveys measure to be a planet, I predict it should be a planet," Morton said, "and everything they measure to be a false positive, I predict to be a false positive."
Using this technique, there are now 1,935 confirmed exoplanets in total, with 1,284 of those being new discoveries. Around 100 of the planets are a similar in size to Earth. The research has been published in The Astrophysical Journal.
All of these planets were discovered by the Kepler prime mission, which involved studying around 150,000 stars in a single patch of sky between 2009 and 2013.
Of course, the point of all this planet-spotting is to try to answer the big question "are we alone in the Universe?" To try to figure this out, Kepler scientists can use the transit signal of planets to work out their size and how far away they're situated from their sun, which provides some indication of whether planets could possibly host life.
Based on those criteria, the new announcement includes nine planets that are listed as potentially habitable. In this context, that means they're less than twice the size of Earth and are situated in the 'Goldilocks zone' of their star, meaning they're not too close or far away and could potentially contain liquid water.
That doesn't mean in any way that these planets do host life, or even that they could. But without being able to study these planets in closer detail, this is the best way we have to assess a planet's suitability for life as we know it.
The ultimate goal is to be able to detect the light coming from one of these potentially habitable exoplanets so that we can analyse the gases in its atmosphere, which will tell us more about whether life ever existed there, or if it could in future.
The sad news in all of this is that Kepler is almost at the end of its planet-hunting mission. It's going to continue to observe strange astronomical phenomena for the foreseeable future, but it's predicted to run out of fuel in around two years, in the Northern Hemisphere summer of 2018.
The baton is being handed to the Transiting Exoplanet Survey Satellite (TESS) and James Webb Space Telescope, which together will be able to scan even more stars in the night sky, and hopefully tell us more information about the alien worlds orbiting them.
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