Planet Hunters discovers new Jupiter-sized planet

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Photo by Karen Tian.

Researchers have confirmed the existence of a Jupiter-sized planet which may have satellites conducive to life.

Earlier this month, researchers with the collaborative group Planet Hunters confirmed with 99.9 percent confidence the discovery of the planet, named PH2 b, in the Milky Way orbiting its star’s habitable zone — a range of distances from the star where Earth-like planets could have liquid water and support life. It also announced 42 new planet candidates, including 20 located in their respective stars’ habitable zones. The results, which can be found on the Planet Hunters website, have been submitted to The Astrophysical Journal.

“The planet PH2 b itself cannot sustain life because it is a gas planet,” said Ji Wang, an astrophysics postdoctoral associate at Yale and lead author of the paper. “But this kind of gas giant usually has many satellites — take Jupiter and Saturn as examples. If the distance of the planet to its star is right, its satellite could be habitable.”

Planet Hunters is a collaborative project designed by Yale University and Zooniverse, an online collection of citizen science projects, that allows citizen scientists to look for exoplanets -— planets orbiting stars other than the sun — using data from the NASA Kepler space telescope public archives. Volunteers look at star brightness levels, or “light curves,” to search for possible planet transits, as indicated by a dip in brightness when a planet passes in front of the star. Then, project scientists “rule out false positives, and planets can be confirmed,” Wang said. Citizen scientists who contribute to the identification are acknowledged on the website or as co-authors.

“These discoveries highlight the power of eyeballs,” said Meg Schwamb, a Yale astrophysics postdoctoral fellow working with Planet Hunters. “We have 200,000 friends who can look through the data.”

The website’s streamlined interface allows volunteers to analyze a light curve in five to 10 seconds, said Debra Fischer, a Yale professor of astronomy and Planet Hunters co-founder.

“We present data in a way that’s accessible to everyone, and we try hard to show the public what we’re doing and how we’re doing it,” Schwamb said. “We bridge the gap between scientists and nonscientists by bringing them in on the ground level.”

The Kepler public archive releases data that has already been scrutinized by scientists, but Planet Hunters, using the same data, has found almost double the number of gas giants in the habitable zone.

Fischer said that because of the computational techniques it uses, Kepler finds exoplanets that are “strongly biased toward being closer to their stars” and thus less likely to be in the habitable zone. Planet Hunters, on the other hand, can detect “planets in very wide or longer orbital periods, which have less dips in the light curve from transit,” and which Kepler algorithms overlook, Fischer said. Nine of the recent planet candidates discussed in Wang’s paper have orbital periods of over 400 days, and most have periods longer than 100 days.

The researchers said the volunteers’ discoveries can help the Kepler team improve its computer algorithms.

“We are entering this era of ‘big data,’” Schwamb said. “We need to find a way to go from gigabytes to terabytes. You can’t use citizen science alone, but machine learning will be much better with input from citizen science. It can ‘train’ an algorithm — this is where citizen science is going.”

The research team presented their Planet Hunters findings to the American Astronomical Society earlier this month.

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