A star called KIC 8462852 has been in the news recently for
unexplained and bizarre behavior. NASA's Kepler mission had monitored
the star for four years, observing two unusual incidents, in 2011 and
2013, when the star's light dimmed in dramatic, never-before-seen ways.
Something had passed in front of the star and blocked its light, but
what?
Scientists first reported the findings in September, suggesting a
family of comets as the most likely explanation. Other cited causes
included fragments of planets and asteroids.
A new study using data from NASA's Spitzer Space Telescope addresses
the mystery, finding more evidence for the scenario involving a swarm of
comets. The study, led by Massimo Marengo of Iowa State University,
Ames, is accepted for publication in the Astrophysical Journal Letters.
One way to learn more about the star is to study it in infrared
light. Kepler had observed it in visible light. If a planetary impact,
or a collision amongst asteroids, were behind the mystery of KIC
8462852, then there should be an excess of infrared light around the
star. Dusty, ground-up bits of rock would be at the right temperature to
glow at infrared wavelengths.
At first, researchers tried to look for infrared light using NASA's
Wide-Field Infrared Survey Explorer, or WISE, and found none. But those
observations were taken in 2010, before the strange events seen by
Kepler -- and before any collisions would have kicked up dust.
To search for infrared light that might have been generated after the
oddball events, researchers turned to Spitzer, which, like WISE, also
detects infrared light. Spitzer just happened to observe KIC 8462852
more recently in 2015.
"Spitzer has observed all of the hundreds of thousands of stars where
Kepler hunted for planets, in the hope of finding infrared emission
from circumstellar dust," said Michael Werner, the Spitzer project
scientist at NASA's Jet Propulsion Laboratory in Pasadena, California,
and the lead investigator of that particular Spitzer/Kepler observing
program.
But, like WISE, Spitzer did not find any significant excess of
infrared light from warm dust. That makes theories of rocky smashups
very unlikely, and favors the idea that cold comets are responsible.
It's possible that a family of comets is traveling on a very long,
eccentric orbit around the star. At the head of the pack would be a very
large comet, which would have blocked the star's light in 2011, as
noted by Kepler. Later, in 2013, the rest of the comet family, a band of
varied fragments lagging behind, would have passed in front of the star
and again blocked its light.
By the time Spitzer observed the star in 2015, those comets would be
farther away, having continued on their long journey around the star.
They would not leave any infrared signatures that could be detected.
According to Marengo, more observations are needed to help settle the case of KIC 8462852.
"This is a very strange star," he said. "It reminds me of when we
first discovered pulsars. They were emitting odd signals nobody had ever
seen before, and the first one discovered was named LGM-1 after 'Little
Green Men.'"
In the end, the LGM-1 signals turned out to be a natural phenomenon.
"We may not know yet what's going on around this star," Marengo observed. "But that's what makes it so interesting."
Ames manages the Kepler and K2 missions for NASA's Science Mission
Directorate. JPL managed Kepler mission development. Ball Aerospace
& Technologies Corp. operates the flight system with support from
the Laboratory for Atmospheric and Space Physics at the University of
Colorado in Boulder.
JPL manages the Spitzer Space Telescope mission for NASA's Science
Mission Directorate, Washington. Science operations are conducted at the
Spitzer Science Center at the California Institute of Technology in
Pasadena. Spacecraft operations are based at Lockheed Martin Space
Systems Company, Littleton, Colorado. Data are archived at the Infrared
Science Archive housed at the Infrared Processing and Analysis Center at
Caltech.
Caltech manages JPL for NASA.
For more information about Kepler and Spitzer, respectively, visit:
http://www.nasa.gov/kepler
http://kepler.nasa.gov
http://www.nasa.gov/spitzer
http://www.spitzer.caltech.edu
Media Contact
Whitney Clavin
Jet Propulsion Laboratory, Pasadena, California
818-354-4673
whitney.clavin@jpl.nasa.gov
Michele Johnson
Ames Research Center, Moffett Field, Calif.
650-604-6982
michele.johnson@nasa.gov
Source: JPL - Caltech
