[meteorite-list] NASA's WISE Survey Finds Thousands of New Stars, But No 'Planet X'

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri, 7 Mar 2014 13:12:21 -0800 (PST)
Message-ID: <201403072112.s27LCL2a011114_at_zagami.jpl.nasa.gov>

     
March 7, 2014
     
RELEASE 14-067
     
NASA's WISE Survey Finds Thousands of New Stars, But No 'Planet X'

After searching hundreds of millions of objects across our sky, NASA's
Wide-Field Infrared Survey Explorer (WISE) has turned up no evidence of the
hypothesized celestial body in our solar system commonly dubbed "Planet X."

Researchers previously had theorized about the existence of this large, but
unseen celestial body, suspected to lie somewhere beyond the orbit of Pluto.
In addition to "Planet X," the body had garnered other nicknames, including
"Nemesis" and "Tyche."

This recent study, which involved an examination of WISE data covering the
entire sky in infrared light, found no object the size of Saturn or larger
exists out to a distance of 10,000 astronomical units (au), and no object
larger than Jupiter exists out to 26,000 au. One astronomical unit equals 93
million miles. Earth is 1 au, and Pluto about 40 au, from the sun.

"The outer solar system probably does not contain a large gas giant planet,
or a small, companion star," said Kevin Luhman of the Center for Exoplanets
and Habitable Worlds at Penn State University, University Park, Pa., author
of a paper in the Astrophysical Journal describing the results.

But searches of the WISE catalog are not coming up empty. A second study
reveals several thousand new residents in our sun's "backyard," consisting of
stars and cool bodies called brown dwarfs.

"Neighboring star systems that have been hiding in plain sight just jump out
in the WISE data," said Ned Wright of the University of California, Los
Angeles, the principal investigator of the mission.

The second WISE study, which concentrated on objects beyond our solar system,
found 3,525 stars and brown dwarfs within 500 light-years of our sun.

"We're finding objects that were totally overlooked before," said Davy
Kirkpatrick of NASA's Infrared and Processing Analysis Center at the
California Institute of Technology, Pasadena, Calif. Kirkpatrick is lead
author of the second paper, also in the Astrophysical Journal. Some of these
3,525 objects also were found in the Luhman study, which catalogued 762
objects.

The WISE mission operated from 2010 through early 2011, during which time it
performed two full scans of the sky -- with essentially a six-month gap
between scans. The survey captured images of nearly 750 million asteroids,
stars and galaxies. In November 2013, NASA released data from the AllWISE
program, which now enables astronomers to compare the two full-sky surveys to
look for moving objects.

In general, the more an object in the WISE images appears to move over time,
the closer it is. This visual clue is the same effect at work when one
observes a plane flying low to the ground versus the same plane flying at
higher altitude. Though traveling at the same speed, the plane at higher
altitude will appear to be moving more slowly.

Searches of the WISE data catalog for these moving objects are uncovering
some of the closest stars. The discoveries include a star located about 20
light-years away in the constellation Norma, and as reported last March, a
pair of brown dwarfs only 6.5 light-years away -- making it the closest star
system to be discovered in nearly a century.

Despite the large number of new solar neighbors found by WISE, "Planet X" did
not show up. Previous speculations about this hypothesized body stemmed in
part from geological studies that suggested a regular timing associated with
mass extinctions on Earth. The idea was that a large planet or small star
hidden in the farthest reaches of our solar system might periodically sweep
through bands of outer comets, sending them flying toward our planet. The
Planet X-based mass extinction theories were largely ruled out even prior to
the new WISE study.

Other theories based on irregular comet orbits had also postulated a Planet
X-type body. The new WISE study now argues against these theories as well.

Both of the WISE searches were able to find objects the other missed,
suggesting many other celestial bodies likely await discovery in the WISE
data.

"We think there are even more stars out there left to find with WISE. We
don't know our own sun's backyard as well as you might think," said Wright.

WISE was put into hibernation upon completing its primary mission in 2011. In
September 2013, it was reactivated, renamed NEOWISE and assigned a new
mission to assist NASA's efforts to identify the population of potentially
hazardous near-Earth objects. NEOWISE will also characterize previously known
asteroids and comets to better understand their sizes and compositions.

More information on WISE and NEOWISE can be found online at:

http://www.nasa.gov/wise

-end-

J.D. Harrington
Headquarters, Washington
202-358-5241
j.d.harrington at nasa.gov

Whitney Clavin
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-4673
whitney.clavin at jpl.nasa.gov
Received on Fri 07 Mar 2014 04:12:21 PM PST