Pulverized Planet Dust May Lie Around Double Stars (Spitzer)

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http://www.jpl.nasa.gov/news/news.cfm?release=2010-275

Pulverized Planet Dust May Lie Around Double Stars
Jet Propulsion Laboratory
August 23, 2010

PASADENA, Calif. -- Tight double-star systems might not be the best
places for life to spring up, according to a new study using data from
NASA's Spitzer Space Telescope. The infrared observatory spotted a
surprisingly large amount of dust around three mature, close-orbiting
star pairs. Where did the dust come from? Astronomers say it might be
the aftermath of tremendous planetary collisions.

"This is real-life science fiction," said Jeremy Drake of the
Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass. "Our data
tell us that planets in these systems might not be so lucky --
collisions could be common. It's theoretically possible that habitable
planets could exist around these types of stars, so if there happened to
be any life there, it could be doomed."

Drake is the principal investigator of the research, published in the
Aug.19 issue of the Astrophysical Journal Letters.

The particular class of binary, or double, stars in the study are about
as snug as stars get. Named RS Canum Venaticorums, or RS CVns for short,
they are separated by only about two-million miles (3.2-million
kilometers), or two percent of the distance between Earth and our sun.
The stellar pairs orbit around each other every few days, with one face
on each star perpetually locked and pointed toward the other.

The close-knit stars are similar to the sun in size and are probably
about a billion to a few billion years old -- roughly the age of our sun
when life first evolved on Earth. But these stars spin much faster, and,
as a result, have powerful magnetic fields, and giant, dark spots. The
magnetic activity drives strong stellar winds -- gale-force versions of
the solar wind -- that slow the stars down, pulling the twirling duos
closer over time. And this is where the planetary chaos may begin.

As the stars cozy up to each other, their gravitational influences
change, and this could cause disturbances to planetary bodies orbiting
around both stars. Comets and any planets that may exist in the systems
would start jostling about and banging into each other, sometimes in
powerful collisions. This includes planets that could theoretically be
circling in the double stars' habitable zone, a region where
temperatures would allow liquid water to exist. Though no habitable
planets have been discovered around any stars beyond our sun at this
point in time, tight double-star systems are known to host planets; for
example, one system not in the study, called HW Vir, has two gas-giant
planets.

"These kinds of systems paint a picture of the late stages in the lives
of planetary systems," said Marc Kuchner, a co-author from NASA Goddard
Space Flight Center in Greenbelt, Md. "And it's a future that's messy
and violent."

Spitzer spotted the infrared glow of hot dusty disks, about the
temperature of molten lava, around three such tight binary systems. One
of the systems was originally flagged as having a suspicious excess of
infrared light in 1983 by the Infrared Astronomical Satellite. In
addition, researchers using Spitzer recently found a warm disk of debris
around another star that turned out to be a tight binary system.

The astronomy team says that dust normally would have dissipated and
blown away from the stars by this mature stage in their lives. They
conclude that something -- most likely planetary collisions -- must
therefore be kicking up the fresh dust. In addition, because dusty disks
have now been found around four, older binary systems, the scientists
know that the observations are not a fluke. Something chaotic is very
likely going on.

If any life forms did exist in these star systems, and they could look
up at the sky, they would have quite a view. Marco Matranga, first
author of the paper, from the Harvard-Smithsonian Center for
Astrophysics and now a visiting astronomer at the Palermo Astronomical
Observatory in Sicily, said, "The skies there would have two huge suns,
like the ones above the planet Tatooine in 'Star Wars.'"

Other authors include V.L. Kashyap of the Harvard-Smithsonian Center for
Astrophysics; and Massimo Marengo of Iowa State University, Ames.

The Spitzer observations were made before it ran out of its liquid
coolant in May 2009, officially beginning its warm mission.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., 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, also in Pasadena.
Caltech manages JPL for NASA. For more information about Spitzer, visit
http://spitzer.caltech.edu/ and http://www.nasa.gov/spitzer .

The Infrared Astronomical Satellite, known commonly by its acronym,
IRAS, was a joint project between NASA, the Netherlands and the United
Kingdom.

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
Whitney...@jpl.nasa.gov

2010-275