NASA's WISE Survey Finds Thousands of New Stars, But No 'Planet X'

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NASA's WISE Survey Finds Thousands of New Stars, But No 'Planet X'

WASHINGTON, March 7, 2014 /PRNewswire-USNewswire/ -- 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

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SOURCE NASA

-0- 03/07/2014

/CONTACT: J.D. Harrington, Headquarters, Washington, 202-358-5241, j.d.harrington@nasa.gov, or Whitney Clavin, Jet Propulsion Laboratory, Pasadena, Calif., 818-354-4673, whitney.clavin@jpl.nasa.gov

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