In a historic discovery, Nasa scientists have found an eighth planet orbiting a distant star – the first time this number of planets has been observed orbiting a single star outside our own solar system.
The planet - known as Kepler-90i - circles the Sun-like star Kepler-90 which lies 2,545 light years from Earth. It was discovered using data collected from the Kepler Space Telescope and state-of-the-art machine learning technology provided by Google.
"Just as we expected, there are exciting discoveries lurking in our archived Kepler data, waiting for the right tool or technology to unearth them," said Paul Hertz, director of NASA's Astrophysics Division in Washington. "This finding shows that our data will be a treasure trove available to innovative researchers for years to come."
The technology mimics the connections between neurons in the brain to create an artificial "neural network". To find the previously missed eighth planet, it sifted through Kepler's data to identify weak signals coming from the the Kepler-90 system.
The latest research, which has been accepted for publication in The Astronomical Journal, shows the promise of machine-learning techniques in identifying the weakest signals from distant worlds.
Kepler-90i shows little promise for finding life, however. It's a scorching hot, rocky planet with an average temperature that is believed to exceed 800 degrees Fahrenheit - around the same as Mercury. It is around 30% larger than Earth and orbits its star once every 14.4 days.
"The Kepler-90 star system is like a mini version of our solar system. You have small planets inside and big planets outside, but everything is scrunched in much closer," said Andrew Vanderburg, a NASA astronomer at the University of Texas at Austin.
When the ground-breaking Kepler mission launched in March 2009, scientists didn't know how common planets were beyond our solar system. But thanks to the unprecedented amounts of data it has provided, astronomers now believe there may be at least one planet orbiting every star in the sky.
"These results demonstrate the enduring value of Kepler's mission," said Jessie Dotson, Kepler's project scientist at NASA's Ames Research Center.
"New ways of looking at the data – such as this early-stage research to apply machine learning algorithms – promises to continue to yield significant advances in our understanding of planetary systems around other stars. I'm sure there are more firsts in the data waiting for people to find them."