Usingdata from NASA's Keplerspace telescope, citizen scientists have discovered a planet roughlytwice the size of Earth located within its star's habitable zone, the range oforbital distances where liquid water may exist on the planet's surface. The newworld, known as K2-288Bb, could be rocky or could be a gas-rich planet similarto Neptune. Its size is rare among exoplanets - planets beyond our solarsystem.

"It'sa very exciting discovery due to how it was found, its temperate orbit and becauseplanets of this size seem to be relatively uncommon," said Adina Feinstein,a University of Chicago graduate student who discussed the discovery on Monday,Jan. 7, at the 233rd meeting of the American Astronomical Society in Seattle.She is also the lead author of a paper describing the new planet accepted forpublication by TheAstronomical Journal.

Located226 light-years away in the constellation Taurus, the planet lies in a stellarsystem known as K2-288, which contains a pair of dim, cool M-type starsseparated by about 5.1 billion miles (8.2 billion kilometers) - roughly sixtimes the distance between Saturn and the Sun. The brighter star is about halfas massive and large as the Sun, while its companion is about one-third the Sun'smass and size. The new planet, K2-288Bb, orbits the smaller, dimmer star every31.3 days.

In2017, Feinstein and Makennah Bristow, an undergraduate student at theUniversity of North Carolina Asheville, worked as interns with Joshua Schlieder,an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland.They searched Kepler data for evidence of transits, the regular dimming of astar when an orbiting planet moves across the star's face.

Examiningdata from the fourth observing campaignof Kepler's K2mission, the team noticed two likely planetary transits in the system.But scientists require a third transit before claiming the discovery of a candidateplanet, and there wasn't a third signal in the observations they reviewed.

Asit turned out, though, the team wasn't actually analyzing all of the data.

InKepler's K2 mode, which ran from 2014 to 2018, the spacecraft repositioneditself to point at a new patch of sky at the start of each three-monthobserving campaign. Astronomers were initially concerned that thisrepositioning would cause systematic errors in measurements.

"Re-orientingKepler relative to the Sun caused miniscule changes in the shape of thetelescope and the temperature of the electronics, which inevitably affectedKepler's sensitive measurements in the first days of each campaign," saidco-author Geert Barentsen, an astrophysicist at NASA's Ames Research Center inCalifornia's Silicon Valley and the director of the guest observer office forthe Kepler and K2 missions.

Todeal with this, early versions of the software that was used to prepare thedata for planet-finding analysis simply ignored the first few days ofobservations - and that's where the third transit was hiding.

Asscientists learned how to correct for these systematic errors, this trimmingstep was eliminated - but the early K2 data Barstow studied had been clipped.

"Weeventually re-ran all data from the early campaigns through the modifiedsoftware and then re-ran the planet search to get a list of candidates, butthese candidates were never fully visually inspected," explained Schlieder,a co-author of the paper. "Inspecting, or vetting, transits with the humaneye is crucial because noise and other astrophysical events can mimic transits."

Instead,the re-processed data were posted directly to ExoplanetExplorers, a project where the public searches Kepler's K2 observationsto locate new transiting planets. In May 2017, volunteers noticed the thirdtransit and began an excited discussion about what was then thought to be anEarth-sized candidate in the system, which caught the attention of Feinsteinand her colleagues.

"That'show we missed it - and it took the keen eyes of citizen scientists to make thisextremely valuable find and point us to it," Feinstein said.

Theteam began follow-up observations using NASA'sSpitzer Space Telescope, the Keck II telescope at the W. M. KeckObservatory and NASA's Infrared Telescope Facility(the latter two in Hawaii), and also examined data from ESA's (the EuropeanSpace Agency's) Gaiamission.

Estimatedto be about 1.9 times Earth's size, K2-288Bb is half the size of Neptune. This placesthe planet within a recentlydiscovered category called the Fulton gap, or radius gap. Amongplanets that orbit close to their stars, there's a curious dearth of worlds betweenabout 1.5 and two times Earth's size. This is likely the result of intensestarlight breaking up atmospheric molecules and eroding away the atmospheres ofsome planets over time, leaving behind two populations. Since K2-288Bb's radiusplaces it in this gap, it may provide a case study of planetary evolutionwithin this size range.

OnOct. 30, 2018, Kepler ran out of fuel and ended its mission after nine years,during which it discovered 2,600 confirmed planets around other stars - thebulk of those now known - along with thousands of additional candidatesastronomers are working to confirm. And while NASA'sTransiting Exoplanet Survey Satellite is the newest space-basedplanet hunter, this new finding shows that more discoveries await scientists inKepler data.

Ames manages the Kepler and K2 missions for NASA's Science MissionDirectorate. NASA's Jet Propulsion Laboratory in Pasadena, California, managedKepler mission development. Ball Aerospace & Technologies Corporationoperated the flight system with support from the Laboratory for Atmospheric andSpace Physics at the University of Colorado in Boulder.

Formore information about the Kepler and K2 missions, visit:

Kepler

News Media Contact

Calla CofieldJet Propulsion Laboratory, Pasadena, Calif.626-808-2469calla.e.cofield@jpl.nasa.gov

By Francis ReddyNASA's Goddard Space Flight Center, Greenbelt, Md.

2019-002

Go here to read the rest:

Citizen Scientists Find New World with NASA Telescope