Our Milky Way galaxy is full of hundreds of billions of
worlds just waiting to be found. In 2014, scientists using data from our planet-hunting
Kepler space telescope discovered seven planets orbiting Kepler-90, a Sun-like star
located 2,500 light-years away. Now, an eighth planet has been identified in this
planetary system, making it tied with our own solar system in having the highest
number of known planets. Here’s what you need to know:
The new planet is called Kepler-90i.
Kepler-90i is a sizzling hot, rocky planet. It’s the smallest of eight planets in the Kepler-90 system. It orbits so close to its star that a “year” passes in just 14 days.
Average surface temperatures on Kepler-90i are estimated to hover around 800 degrees Fahrenheit, making it an unlikely place for life as we know it.
Its planetary system is like a scrunched up version of our solar system.
The Kepler-90 system is set up like our solar system, with the small planets located close to their star and the big planets farther away. This pattern is evidence that the system’s outer gas planets—which are about the size of Saturn and Jupiter—formed in a way similar to our own.
But the orbits are much more compact. The orbits of all eight
planets could fit within the distance of Earth’s orbit around our Sun! Sounds
crowded, but think of it this way: It would make for some great planet-hopping.
Kepler-90i was discovered using machine learning.
Most planets beyond our solar system are too far away to be imaged directly. The Kepler space telescope searches for these exoplanets—those planets orbiting stars beyond our solar system—by measuring how the brightness of a star changes when a planet transits, or crosses in front of its disk. Generally speaking, for a given star, the greater the dip in brightness, the bigger the planet!
Researchers trained a computer to learn how to identify the faint signal of transiting exoplanets in Kepler’s vast archive of deep-space data. A search for new worlds around 670 known multiple-planet systems using this machine-learning technique yielded not one, but two discoveries: Kepler-90i and Kepler-80g. The latter is part of a six-planet star system located 1,000 light-years away.
is just the beginning of a new way of planet hunting.
Kepler-90 is the first known star system besides our own that has eight planets, but scientists say it won’t be the last. Other planets may lurk around stars surveyed by Kepler. Next, researchers are using machine learning with sophisticated computer algorithms to search for more planets around 150,000 stars in the Kepler database.
the meantime, we’ll be doing more searching with telescopes.
Kepler is the most successful planet-hunting spacecraft to date, with more than 2,500 confirmed exoplanets and many more awaiting verification. Future space missions, like the Transiting Exoplanet Survey Satellite (TESS), the James Webb Space Telescope and Wide-Field Infrared Survey Telescope (WFIRST) will continue the search for new worlds and even tell us which ones might offer promising homes for extraterrestrial life.
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*All images of exoplanets
are artist illustrations.