NASA Discovered Solar System Like Ours.
For the first time, NASA has found a star system with as many planets as our own. It could not have done so, however, without two unlikely sources of help: Google software engineers and the decision to strip Pluto of its status as a planet. NASA announced on 14 December 2017 that a reanalysis of the data from its Kepler space telescope, which has already found more than 1,000 planets, had identified a faint signal in a system 2,500 light years from Earth. This small world, Kepler-90i, would ordinarily be unremarkable. Its surface would be “sizzling hot” as it orbits close to its star, NASA scientists said, and it is not a contender for harbouring life. However, its discovery meant that its system had eight verified planets. “This ties Kepler 90 with our solar system for having the most known planets,” said Paul Hertz, director of astrophysics at NASA, which has not counted Pluto as a planet since 2006. Just as significantly, NASA hopes that the manner of its discovery, thanks to artificial intelligence software, will open up a new front in astronomy.
The Kepler space telescope identifies planets by scanning the light coming from stars and looking for the faint dimming caused by a planet passing in front of them. To spot this requires analysing vast quantities of data. That was why Christopher Shallue, an engineer at Google, thought his company could help. “In my spare time, I started googling for ‘finding exoplanets with large data sets’ and found out about the Kepler mission and the huge data set available,” he said. “Machine learning shines in situations where there is so much data that humans can’t search it for themselves.” With NASA, he trained a “neural network” by using 15,000 previously vetted signals from the Kepler mission. This programme, which learns patterns in a way roughly analogous to a human brain, was able to look through the data collected by Kepler to see if it missed any similar planetary signals in the 670 star systems known to exist. By doing this, NASA was able to find two new planets, one of which was Kepler- 90i. The other, Kepler-80g, was in a system containing six planets. Andrew Vanderburg, from NASA, worked with Mr Shallue. He said that the faintness of the signals made it difficult. “We got lots of false positives of planets, but also potentially more real planets,” he said. “It’s like sifting through rocks to find jewels. If you have a finer sieve, then you will catch more rocks, but you might catch more jewels as well.”
NASA’s much-hyped press conference, announced a week in advance, disappointed some. There had been rumours that it would confirm a significant progress in the search for extraterrestrial life and bookmakers had lowered the odds of finding aliens. Dr Vanderburg said that people should still be excited. He said that they might not have noticed the last planet orbiting Kepler-90. “It would almost be surprising to me if there weren’t more,” he said. “This is the first exoplanet system with eight planets, but almost certainly not the last . . . Maybe there are systems out there with so many planets they make our system seem ordinary.”
Credit: Tom Whipple for The Times, 15 December 2017.