This artist's conception shows the object
named WISE J085510.83-071442.5, the coldest known brown dwarf. Brown
dwarfs are dim star-like bodies that lack the mass to burn nuclear fuel
as stars do. Full image and caption
This animation shows the coldest brown dwarf
yet seen, and the fourth closest system to our sun. Called WISE
J085510.83-071442.5, this dim object was discovered through its rapid
motion across the sky. Full image and caption - enlarge image
This diagram illustrates the locations of
the star systems closest to the sun. The year when the distance to each
system was determined is listed after the system's name. Full image and caption - enlarge image
NASA's Wide-field Infrared Survey Explorer (WISE) and Spitzer Space
Telescope have discovered what appears to be the coldest "brown dwarf"
known -- a dim, star-like body that surprisingly is as frosty as
Earth's North Pole.
Images from the space telescopes also pinpointed the object's
distance to 7.2 light-years away, earning it the title for fourth
closest system to our sun. The closest system, a trio of stars, is Alpha
Centauri, at about 4 light-years away.
"It's very exciting to discover a new neighbor of our solar system
that is so close," said Kevin Luhman, an astronomer at Pennsylvania
State University's Center for Exoplanets and Habitable Worlds,
University Park. "And given its extreme temperature, it should tell us a
lot about the atmospheres of planets, which often have similarly cold
temperatures."
Brown dwarfs start their lives like stars, as collapsing balls of
gas, but they lack the mass to burn nuclear fuel and radiate starlight.
The newfound coldest brown dwarf is named WISE J085510.83-071442.5. It
has a chilly temperature between minus 54 and 9 degrees Fahrenheit
(minus 48 to minus 13 degrees Celsius). Previous record holders for
coldest brown dwarfs, also found by WISE and Spitzer, were about room
temperature.
WISE was able to spot the rare object because it surveyed the entire
sky twice in infrared light, observing some areas up to three times.
Cool objects like brown dwarfs can be invisible when viewed by
visible-light telescopes, but their thermal glow -- even if feeble --
stands out in infrared light. In addition, the closer a body, the more
it appears to move in images taken months apart. Airplanes are a good
example of this effect: a closer, low-flying plane will appear to fly
overhead more rapidly than a high-flying one.
"This object appeared to move really fast in the WISE data," said Luhman. "That told us it was something special."
After noticing the fast motion of WISE J085510.83-071442.5 in March
of 2013, Luhman spent time analyzing additional images taken with
Spitzer and the Gemini South telescope on Cerro Pachon in Chile.
Spitzer's infrared observations helped determine the frosty temperature
of the brown dwarf. Combined detections from WISE and Spitzer, taken
from different positions around the sun, enabled the measurement of its
distance through the parallax effect. This is the same principle that
explains why your finger, when held out right in front of you, appears
to jump from side to side when you alternate left- and right-eye views.
"It is remarkable that even after many decades of studying the sky,
we still do not have a complete inventory of the sun's nearest
neighbors," said Michael Werner, the project scientist for Spitzer at
NASA's Jet Propulsion Laboratory in Pasadena, Calif. JPL manages and
operates Spitzer. "This exciting new result demonstrates the power of
exploring the universe using new tools, such as the infrared eyes of
WISE and Spitzer."
WISE J085510.83-071442.5 is estimated to be 3 to 10 times the mass of
Jupiter. With such a low mass, it could be a gas giant similar to
Jupiter that was ejected from its star system. But scientists estimate
it is probably a brown dwarf rather than a planet since brown dwarfs are
known to be fairly common. If so, it is one of the least massive brown
dwarfs known.
In March of 2013, Luhman's analysis of the images from WISE uncovered
a pair of much warmer brown dwarfs at a distance of 6.5 light years,
making that system the third closest to the sun. His search for rapidly
moving bodies also demonstrated that the outer solar system probably
does not contain a large, undiscovered planet, which has been referred
to as "Planet X" or "Nemesis."
For more information on NASA's WISE mission, visit: http://www.nasa.gov/wise
For more information on NASA's Spitzer mission, visit: http://www.nasa.gov/spitzer
The California Institute of Technology in Pasadena manages JPL for NASA.
Whitney Clavin
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-4673
whitney.clavin@jpl.nasa.gov
J.D. Harrington
NASA Headquarters, Washington
202-358-5241
j.d.harrington@nasa.gov
