[meteorite-list] Strange Star Likely Swarmed by Comets

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 24 Nov 2015 16:51:09 -0800 (PST)
Message-ID: <201511250051.tAP0p9b1015089_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.php?feature=4777

Strange Star Likely Swarmed by Comets
Jet Propulsion Laboratory
November 24, 2015

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 at jpl.nasa.gov

Michele Johnson
Ames Research Center, Moffett Field, Calif.
650-604-6982
michele.johnson at nasa.gov

2015-357
Received on Tue 24 Nov 2015 07:51:09 PM PST