How AI Found the First Eight-Planet Solar System Beyond Our Own
To much fanfare, NASA just announced the discovery of a new rocky planet, Kepler-90i. Orbiting a star some 2,545 light years away, the new planet is roughly 1.3 times the size of Earth and blistering hot—around 800 degrees Fahrenheit. The find is unique for a few reasons: For one, Kepler-90i is the eighth planet in the previously discovered Kepler-90 solar system, making this far-off system the only family of exoplanets with as many planets as our own.
But perhaps more impressive is how researchers found the planet: by using a Google-developed artificial neural network. The basic idea behind neural networks is that, instead of programming specific rules into a computer, researchers feed that computer a large set of data and the system develops its own way to accomplish the specific task. Layers of computer “neurons” each do simple computations, passing the output on to another layer, says Chris Shallue, a Google software engineer specializing in neural networks, in a press conference.
Such systems have previously been used to translate between languages, identify breast cancer tumors, or even identify hotdogs vs. not hotdogs. “Our idea was to turn this technique to the skies and teach a machine learning system how to identify planets around far away stars,” Shallue says. His team’s results have been accepted for publication in the The Astronomical Journal.
To use this kind of system for exoplanet hunting, researchers turned to the vast database of planetary candidates that the space telescope Kepler has amassed since its launch in 2009. Kepler has monitored the brightness of roughly 200,000 stars, watching for faint dips in the light—the telltale sign of an orbiting planet. Researchers or citizen scientists on the ground then sort through this data by hand (sometimes with the help of statistical techniques) to identify the most likely planetary candidates.
It’s a grueling and time-intensive process: From the roughly 35,000 signals of possible exoplanets orbiting stars outside our solar system, researchers have so far confirmed 2,525 exoplanets.“This process is like looking for needles in a haystack,” says Shallue.