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artist's conception portrays the first planet discovered by the Kepler
spacecraft during its K2 mission. A transit of the planet was teased out
of K2's noisier data using ingenious computer algorithms developed by a
CfA researcher. The newfound planet, HIP 116454b, has a diameter of
20,000 miles (two and a half times the size of Earth) and weighs 12
times as much. It orbits its star once every 9.1 days. Credit: David A. Aguilar (CfA).High Resolution (jpg)-Low Resolution (jpg)
Cambridge, MA -To
paraphrase Mark Twain, the report of the Kepler spacecraft's death was
greatly exaggerated. Despite a malfunction that ended its primary
mission in May 2013, Kepler is still alive and working. The evidence
comes from the discovery of a new super-Earth using data collected
during Kepler's "second life."
"Like a phoenix rising from the ashes, Kepler has been reborn and is
continuing to make discoveries. Even better, the planet it found is ripe
for follow-up studies," says lead author Andrew Vanderburg of the
Harvard-Smithsonian Center for Astrophysics (CfA).
NASA's Kepler spacecraft detects planets by looking for transits,
when a star dims slightly as a planet crosses in front of it. The
smaller the planet, the weaker the dimming, so brightness measurements
must be exquisitely precise. To enable that precision, the spacecraft
must maintain a steady pointing.
Kepler's primary mission came to an end when the second of four
reaction wheels used to stabilize the spacecraft failed. Without at
least three functioning reaction wheels, Kepler couldn't be pointed
Rather than giving up on the plucky spacecraft, a team of scientists
and engineers developed an ingenious strategy to use pressure from
sunlight as a virtual reaction wheel to help control the spacecraft. The
resulting second mission, K2, promises to not only continue Kepler's
search for other worlds, but also introduce new opportunities to observe
star clusters, active galaxies, and supernovae.
Due to Kepler's reduced pointing capabilities, extracting useful data
requires sophisticated computer analysis. Vanderburg and his colleagues
developed specialized software to correct for spacecraft movements,
achieving about half the photometric precision of the original Kepler
Kepler's new life began with a 9-day test in February 2014. When
Vanderburg and his colleagues analyzed that data, they found that Kepler
had detected a single planetary transit.
They confirmed the discovery with radial velocity measurements from
the HARPS-North spectrograph on the Telescopio Nazionale Galileo in the
Canary Islands. Additional transits were weakly detected by the
Microvariability and Oscillations of STars (MOST) satellite.
The newfound planet, HIP 116454b, has a diameter of 20,000 miles, two
and a half times the size of Earth. HARPS-N showed that it weighs
almost 12 times as much as Earth. This makes HIP 116454b a super-Earth, a
class of planets that doesn't exist in our solar system. The average
density suggests that this planet is either a water world (composed of
about three-fourths water and one-fourth rock) or a mini-Neptune with an
extended, gaseous atmosphere.
This close-in planet circles its star once every 9.1 days at a
distance of 8.4 million miles. Its host star is a type K orange dwarf
slightly smaller and cooler than our sun. The system is 180 light-years
from Earth in the constellation Pisces.
Since the host star is relatively bright and nearby, follow-up
studies will be easier to conduct than for many Kepler planets orbiting
fainter, more distant stars.
"HIP 116454b will be a top target for telescopes on the ground and in
space," says Harvard astronomer and co-author John Johnson of the CfA.
The research paper reporting this discovery has been accepted for publication in The Astrophysical Journal.
in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics
(CfA) is a joint collaboration between the Smithsonian Astrophysical
Observatory and the Harvard College Observatory. CfA scientists,
organized into six research divisions, study the origin, evolution and
ultimate fate of the universe.
For more information, contact:
David A. Aguilar
Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics