A nearby star stands out in red in this image from
the Second Generation Digitized Sky Survey.
Image Credit:
DSS/NASA/JPL-Caltech
Feature Link:
Data from NASA's Wide-field Infrared Survey
Explorer, or WISE, has found no evidence for a hypothesized body sometimes
referred to as "Planet X."
Image Credit:
Penn State University
Feature Link:
The third closest star system to the sun, called
WISE J104915.57-531906, is at the center of the larger image, which was taken by
NASA's Wide-field Infrared Survey Explorer (WISE).
Image Credit:
NASA/JPL/Gemini
Observatory/AURA/NSF
Feature Link:
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.
JPL managed and operated WISE for NASA's Science Mission Directorate. The
mission was selected competitively under NASA's Explorers Program managed by the
agency's Goddard Space Flight Center in Greenbelt, Md. The science instrument
was built by the Space Dynamics Laboratory in Logan, Utah. The spacecraft was
built by Ball Aerospace & Technologies Corp. in Boulder, Colo. Science
operations and data processing take place at the Infrared Processing and
Analysis Center at the California Institute of Technology in Pasadena. Caltech
manages JPL for NASA. More information is online
NASA
Guillermo Gonzalo Sánchez Achutegui
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