Citizen Scientists Find New World with NASA Telescope
There are thousands of known exoplanets - planets orbiting stars other than our Sun - but citizen scientists have helped discover one that has a rare quality.
Using
data fromNASA's Kepler
space telescope, citizen scientists have discovered a planet roughly
twice the size of Earth located within its star's habitable zone, the range of
orbital distances where liquid water may exist on the planet's surface. The new
world, known as K2-288Bb, could be rocky or could be a gas-rich planet similar
to Neptune. Its size is rare among exoplanets - planets beyond our solar
system."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," 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 for
publication byThe
Astronomical Journal.Located
226 light-years away in the constellation Taurus, the planet lies in a stellar
system known as K2-288, which contains a pair of dim, cool M-type stars
separated by about 5.1 billion miles (8.2 billion kilometers) - roughly six
times the distance between Saturn and the Sun. The brighter star is about half
as massive and large as the Sun, while its companion is about one-third the Sun's
mass and size. The new planet, K2-288Bb, orbits the smaller, dimmer star every
31.3 days.In
2017, Feinstein and Makennah Bristow, an undergraduate student at the
University 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 a
star when an orbiting planet moves across the star's face.Examining
data fromthe fourth observing campaignof Kepler'sK2
mission, the team noticed two likely planetary transits in the system.
But scientists require a third transit before claiming the discovery of a candidate
planet, and there wasn't a third signal in the observations they reviewed.As
it turned out, though, the team wasn't actually analyzing all of the data.In
Kepler's K2 mode, which ran from 2014 to 2018, the spacecraft repositioned
itself to point at a new patch of sky at the start of each three-month
observing campaign. Astronomers were initially concerned that this
repositioning would cause systematic errors in measurements."Re-orienting
Kepler relative to the Sun caused miniscule changes in the shape of the
telescope and the temperature of the electronics, which inevitably affected
Kepler's sensitive measurements in the first days of each campaign," said
co-author Geert Barentsen, an astrophysicist at NASA's Ames Research Center in
California's Silicon Valley and the director of the guest observer office for
the Kepler and K2 missions.To
deal with this, early versions of the software that was used to prepare the
data for planet-finding analysis simply ignored the first few days of
observations - and that's where the third transit was hiding.As
scientists learned how to correct for these systematic errors, this trimming
step was eliminated - but the early K2 data Barstow studied had been clipped."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," explained Schlieder,
a co-author of the paper. "Inspecting, or vetting, transits with the human
eye is crucial because noise and other astrophysical events can mimic transits."Instead,
the re-processed data were posted directly toExoplanet
Explorers, a project where the public searches Kepler's K2 observations
to locate new transiting planets. In May 2017, volunteers noticed the third
transit and began an excited discussion about what was then thought to be an
Earth-sized candidate in the system, which caught the attention of Feinstein
and her colleagues."That's
how we missed it - and it took the keen eyes of citizen scientists to make this
extremely valuable find and point us to it," Feinstein said.The
team began follow-up observations usingNASA's
Spitzer Space Telescope, the Keck II telescope at theW. M. Keck
ObservatoryandNASA's Infrared Telescope Facility(the latter two in Hawaii), and also examined data from ESA's (the European
Space Agency's)Gaia
mission.Estimated
to be about 1.9 times Earth's size, K2-288Bb is half the size of Neptune. This places
the planet within arecently
discovered category called the Fulton gap, or radius gap. Among
planets that orbit close to their stars, there's a curious dearth of worlds between
about 1.5 and two times Earth's size. This is likely the result of intense
starlight breaking up atmospheric molecules and eroding away the atmospheres of
some planets over time, leaving behind two populations. Since K2-288Bb's radius
places it in this gap, it may provide a case study of planetary evolution
within this size range.On
Oct. 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 - the
bulk of those now known - along with thousands of additional candidates
astronomers are working to confirm. And whileNASA's
Transiting Exoplanet Survey Satelliteis the newest space-based
planet hunter, this new finding shows that more discoveries await scientists in
Kepler data.Ames manages the Kepler and K2 missions for NASA's Science Mission
Directorate. NASA's Jet Propulsion Laboratory in Pasadena, California, managed
Kepler mission development. Ball Aerospace & Technologies Corporation
operated the flight system with support from the Laboratory for Atmospheric and
Space Physics at the University of Colorado in Boulder.For
more information about the Kepler and K2 missions, visit:http://www.nasa.gov/kepler