NASA has found our solar system’s twin more than 2500 light-years away. Using data from the Kepler space telescope, researchers have found an eighth planet at the Kepler-90 system, tying our own system for the highest number of known planets. Before the NASA announcement, online rumours had swirled speculating that the press conference might be about discovering aliens. As usual, it was not.
Google software engineer Christopher Shallue and Andrew Vanderburg at the University of Texas at Austin used a neural network – a type of machine learning that mimics the connections between neurons in a brain – to look for new planets in old Kepler data. They trained their algorithm on 15,000 signals that had already been examined by human scientists and either labelled as real exoplanets or not.
Usually, potential exoplanets have to be examined by human researchers to figure out whether they’re really there. But Kepler has collected far too much data for scientists to sift through by hand, and the neural network is much faster.
“The machine learning model was simply able to look at more signals than it would be reasonably possible to expect humans to be able to look at,” Shallue said in a press conference. It only took the model about 2 hours to go through the 15,000 signals in its training data set, he said.
When it was applied to a set of Kepler signals from 670 stars, the model found two new planets. One, called Kepler-80g, orbits a star about 1100 light-years away that has 5 other planets. The other, Kepler-90i, is the eighth planet in its system.
“Kepler-90i is not a place I’d like to go visit,” said Vanderburg. The planet appears to be small and rocky, probably without a thick atmosphere. Because of its orbit close to its star, this world’s surface may reach temperatures as high as 425°C.
All the planets around the star Kepler-90 orbit closer than Earth does to the sun. Closest to the star are two planets slightly larger than Earth, then Kepler-90i, which is the system’s smallest planet, followed by three worlds a bit smaller than Neptune and two gas giants. The setup is similar to our own, so it may help us figure out whether the way the planets in our solar system formed is common.
It is also possible that the distant system has even more planets, since Kepler has only searched the area close in to the star. Soon, our solar system might not be a record-holder for its number of planets at all.
“There’s a lot of unexplored real estate in the Kepler-90 system, and it would almost be surprising to me if there weren’t more planets in the system,” said Vanderburg. “Maybe there are systems out there with so many planets that they make our own 8-planet solar system seem ordinary.”
In other Not Aliens news, the Breakthrough Listen project – a $100 million programme to search for civilizations beyond Earth – searched for radio signals from the interstellar asteroid, ‘Oumuamua. Having examined a quarter of their data, they found no signals that would suggest the rock hosts alien life.
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