AI reveals Kepler-90 planet system is close match to our own
Meteorologist/Science Writer
Thursday, December 14, 2017, 2:40 PM - We were unique until now, with the only eight-planet solar system known, but a Google AI has now discovered that distant star, Kepler-90, has a family of planets just as large as our own.
On Thursday, December 14, NASA hosted a live teleconference, featuring researchers from Google AI, the University of Texas, Austin, and Ames Research Center, to provide us with the details of this latest discovery made with data from the Kepler Space Telescope.
Using an artificial "neural net", patterned off how neurons connect together in the human brain, the researchers applied this to data from the Kepler mission, and it managed to spot two new planets - Kepler-90 i and Kepler-80 g.
The remarkable thing about finding just two planets is what these discoveries add to our database of alien exoplanets.
Below is an artist's depiction of the Kepler 90 planetary system, showing the relative locations and sizes of the Kepler 90 planets, compared to the locations and sizes of the planets in our solar system.
The Kepler 90 planetary system, compared to our own. Credits: NASA/Ames Research Center/Wendy Stenzel
So, with eight planets, the Kepler-90 system comes to match our own system, and it is the only other eight planet system we know of.
According to NASA:
The Kepler-90 planets have a similar configuration to our solar system with small planets found orbiting close to their star, and the larger planets found farther away. In our solar system, this pattern is often seen as evidence that the outer planets formed in a cooler part of the solar system, where water ice can stay solid and clump together to make bigger and bigger planets. The pattern we see around Kepler-90 could be evidence of that same process happening in this system.
The major difference between Kepler-90 and our solar system is size.
A comparative look at Kepler-90 and the inner solar system. redits: NASA/Ames Research Center/Wendy Stenzel
As shown above, the Kepler-90 system is tiny compared to ours, with all eight known planets in the system fitting within the confines of Earth's orbit here.
"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," Andrew Vanderburg, a NASA Sagan Postdoctoral Fellow and astronomer at the University of Texas at Austin, said in a NASA press release on Thursday.
Also, as the above image indicates, with Kepler-90h - an immense gas giant. bigger than Jupiter - is very close to Earth's orbit, and thus may be at the right distance from its star to be in the "habitable zone". If any moons could remain in a stable orbit around it, when it is that close to its neighbour, those moons would also be in the habitable zone, and thus, could have the right temperature for liquid water to exist on the surface.
These may not be the only planets in the Kepler-90 system, though. Kepler has only investigated the space around Kepler-90 that's equivalent to our own inner solar system, thus, out to the orbit of Mars, or perhaps the asteroid belt. With planets in our solar system that reach far beyond that, there is the possibility that Kepler-90's family is even larger, with more gas giants, ice giants like Uranus or Neptune, or icy rocky worlds like Pluto and its cousins in the Kuiper Belt.
The other discovery made by Google's AI is Kepler-80 g. This newfound exoplanet brings the Kepler-80 system up to a total of six planets, still a rare find amoung alien planetary systems, so far. It is described as being an Earth-sized world, and it forms what's known as a "resonant chain" with four other planets in the system. According to NASA, this makes the compact Kepler-80 system very stable, just like the seven-planet TRAPPIST-1 system.
A tally of the known planetary system, sorted by number of planets. Only Kepler-90 and our own solar system occupy the top slot! Credits: NASA/Ames Research Center/Wendy Stenzel and The University of Texas at Austin/Andrew Vanderburg
NASA's Kepler Telescope has been out in space for over eight years now, making amazing discoveries and showing us that our chances of being alone in the universe are much lower than we ever thought. In addition to the mission scientists and citizen scientists spotting alien planets in the data returned by this telescope, computers have been an important boon for these efforts. Whether it is human eyes or compute algorithms, the key to finding alien worlds with Kepler is spotting the signal for a "transit" - the passage of an alien world across the face of its star, from our perspective here, which causes the light from the star to temporarily dim. The size of the planet is directly related to how much the star's light dims as it transits, and the period of time between each transit of the planet gives us an idea of how long it takes to go around the star, and thus how far away it is from that star.
Over three years ago, the Kepler team announced that they were suddenly able to add over 700 confirmed exoplanets to their database, simply by having computers analyze the data for the transits of multiple objects in the same star system. This "Sudden Multiplication of Planets" depended on the idea that multiple stars in the same star system is a very unstable setup, that would break down very quickly, causing most of the stars to be ejected from the system. Thus, the greater the number of transit signals detected for the same star system, the more likely it is that those signals represent planets. Based on this, the team was able to elevate many "candidate" planets straight to "confirmed" planets, skipping the step where they need another telescope to verify their results.
Now, the mission team has enlisted Google AI to help in their efforts. Applying machine learning to the Kepler data, they say that this has resulted in new ways of analyzing the data, and here we have the first results! Along with the official team analyses and the efforts of citizen scientists with Zooniverse, this new tool will make finding exoplanets even easier in the years to come.
Source: NASA
