A group of citizen scientists have discovered a new planet that is almost twice as large as Earth and is located about 226 light-years away in the Taurus constellation.
The alien world, with the catchy name K2-288Bb, is roughly twice the size of Earth, but scientists aren't certain whether it's composed of rock or is a mostly gaseous world, like Neptune. The exoplanet orbits a pair cool stars found within the Taurus constellation, both smaller and dimmer than the sun. The duo are separated by 5.1 billion miles.
K2-288Bb is half the size of Neptune or 1.9 times the size of Earth, placing it in the "Fulton gap" between 1.5 and two times the size of Earth. This is a rare size of exoplanet that makes it perfect for studying planetary evolution because so few have been found.
The planet is in the K2-288 system, contains a pair of M-type stars. Which are dim, cool and orbiting at 5.1 billion miles apart, about six times the distance between Saturn and the sun. The brightest of the two stars is half as massive as our sun, and the other star is one-third of the sun's mass. K2-288Bb orbits the smaller, dimmer star, completing a full orbit every 31.3 days.
"It's a very exciting discovery due to how it was found, its temperate orbit and because planets of this size seem to be relatively uncommon," Adina Feinstein, a University of Chicago graduate student who aided the discovery of K2-288Bb, said in a news release.
Kepler ran out of fuel last year, but algorithms, scientists and citizen scientists continue to scan its massive dataset for dimming patterns created by exoplanet transits.
Although all of the data from the Kepler mission was run through an algorithm to determine potential planet candidates, visual manpower was needed to actually look at the possible planet transits -- or dip in light when a planet passes in front of its star -- in the light curve data. Kepler observed other events that could be mistaken for planet transits by a computer.
Scientists found two transit signatures among data collected during the fourth observing campaign of Kepler's K2 mission, but they were unable to locate a third. Three transits are needed to confirm an exoplanet candidate.
But researchers hadn't seen all the data. During Kepler's K2 phase, the spacecraft's reorienting process introduced data anomalies that forced researchers to ignore the first few days of observations during each new campaign.
Those first three days of data were ignored, and errors were corrected in the rest of the data gathered.
Only later did NASA scientists develop techniques to adjust for the anomalies.
"We eventually re-ran all data from the early campaigns through the modified software and then re-ran the planet search to get a list of candidates, but these candidates were never fully visually inspected," said Joshua Schlieder, an astrophysicist at NASA's Goddard Space Flight Center. "Inspecting, or vetting, transits with the human eye is crucial because noise and other astrophysical events can mimic transits."
Never examined by scientists, the re-processed data was relinquished to the citizen science project Exoplanet Explorers. Participating amateur astronomers located the third transit scientists were looking for, confirming the presence of K2-288Bb.
Citizen scientists found the third transit hiding in those first few days of data that had been all but forgotten.
"It took the keen eyes of citizen scientists to make this extremely valuable find and point us to it," Feinstein said. Follow-up observations were made with multiple telescopes to confirm the exoplanet.
The discovery was announced Monday at the 233rd meeting of the American Astronomical Society in Seattle.
Last year at the American Astronomical Society meeting, it was announced that citizen scientists helped discover five planets between the size of Earth and Neptune around star K2-138, the first multiplanet system found through crowdsourcing.
