New research from scientists using NASA's
Spitzer Space Telescope suggests that a mysterious infrared glow across
our whole sky is coming from stray stars torn from galaxies, which is
shown in this artist's concept. Image credit: NASA/JPL-Caltech › Full image and caption
Spitzer Sees Stray Starlight (Artist's Concept)
New
research from scientists using NASA's Spitzer Space Telescope suggests
that a mysterious infrared glow across our whole sky is coming from
stray stars torn from galaxies. When galaxies grow, they merge and
become gravitationally tangled in a violent process that results in
streams of stars being ripped away from the galaxies. Such streams,
called tidal tails, can be seen in this artist's concept. Scientists say
that Spitzer is picking up the collective glow of stars such as these,
which linger in the spaces between galaxies.
This artwork is adapted, in part, from galaxy images obtained from the NASA/ESA Hubble Space Telescope.
Image credit: NASA/JPL-Caltech
Unmasking a Hidden Glow
The
image on the left shows a portion of our sky, called the Boötes field,
in infrared light, while the image on the right shows a mysterious,
background infrared glow captured by NASA's Spitzer Space Telescope in
the same region of sky. Using Spitzer, researchers were able to detect
this background glow, which spreads across the whole sky, by masking out
light from galaxies and other known sources of light (the masks are the
gray, blotchy marks).
The scientists find that this light is
coming from stray stars that were torn away from galaxies. When galaxies
tangle and merge -- a natural stage of galaxy growth -- stars often get
kicked out in the process. The stars are too faint to be seen
individually, but Spitzer may be seeing their collective glow.
Image credit: NASA/JPL-Caltech/UC Irvine
PASADENA, Calif. - A new study using data from NASA's Spitzer Space
Telescope suggests a cause for the mysterious glow of infrared light
seen across the entire sky. It comes from isolated stars beyond the
edges of galaxies. These stars are thought to have once belonged to the
galaxies before violent galaxy mergers stripped them away into the
relatively empty space outside of their former homes.
"The infrared background glow in our sky has been a huge mystery," said
Asantha Cooray of the University of California at Irvine, lead author of
the new research published in the journal Nature. "We have new evidence
this light is from the stars that linger between galaxies.
Individually, the stars are too faint to be seen, but we think we are
seeing their collective glow."
The findings disagree with another theory explaining the same background
infrared light observed by Spitzer. A group led by Alexander "Sasha"
Kashlinsky of NASA's Goddard Space Flight Center in Greenbelt, Md.,
proposed in June this light, which appears in Spitzer images as a
blotchy pattern, is coming from the very first stars and galaxies.
In the new study, Cooray and colleagues looked at data from a larger
portion of the sky, called the Bootes field, covering an arc equivalent
to 50 full Earth moons. These observations were not as sensitive as
those from the Kashlinsky group's studies, but the larger scale allowed
researchers to analyze better the pattern of the background infrared
light.
"We looked at the Bootes field with Spitzer for 250 hours," said
co-author Daniel Stern of NASA's Jet Propulsion Laboratory in Pasadena,
Calif. "Studying the faint infrared background was one of the core goals
of our survey, and we carefully designed the observations in order to
directly address the important, challenging question of what causes the
background glow."
The team concluded the light pattern of the infrared glow is not
consistent with theories and computer simulations of the first stars and
galaxies. Researchers say the glow is too bright to be from the first
galaxies, which are thought not to have been as large or as numerous as
the galaxies we see around us today. Instead, the scientists propose a
new theory to explain the blotchy light, based on theories of
"intracluster" or "intrahalo" starlight.
Theories predict a diffuse smattering of stars beyond the halos, or
outer reaches, of galaxies, and in the spaces between clusters of
galaxies. The presence of these stars can be attributed to two
phenomena. Early in the history of our universe as galaxies grew in
size, they collided with other galaxies and gained mass. As the
colliding galaxies became tangled gravitationally, strips of stars were
shredded and tossed into space. Galaxies also grow by swallowing smaller
dwarf galaxies, a messy process that also results in stray stars.
"A light bulb went off when reading some research papers predicting the
existence of diffuse stars," Cooray said. "They could explain what we
are seeing with Spitzer."
More research is needed to confirm this sprinkling of stars makes up a
significant fraction of the background infrared light. For instance, it
would be necessary to find a similar pattern in follow-up observations
in visible light. NASA's upcoming James Webb Space Telescope (JWST)
might finally settle the matter for good.
"The keen infrared vision of the James Webb Telescope will be able to
see some of the earliest stars and galaxies directly, as well as the
stray stars lurking between the outskirts of nearby galaxies," said Eric
Smith, JWST's deputy program manager at NASA Headquarters in
Washington. "The mystery objects making up the background infrared light
may finally be exposed."
Other authors include Joseph Smidt, Francesco De Bernardis, Yan Gong and
Christopher C. Frazer of UC Irvine; Matthew L. N. Ashby of the
Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass; Peter R.
Eisenhardt of JPL; Anthony H. Gonzalez of the University of Florida in
Gainesville; Christopher S. Kochanek of Ohio State University in
Columbus; Szymon Kozłowski of Ohio State and the Warsaw University
Observatory in Poland; and Edward L. Wright of the University of
California, Los Angeles.
JPL manages the Spitzer Space Telescope mission for NASA's Science
Mission Directorate in Washington. Science operations are conducted at
the Spitzer Science Center at the California Institute of Technology in
Pasadena. Data are archived at the Infrared Science Archive housed at
the Infrared Processing and Analysis Center at Caltech. Caltech manages
JPL for NASA.
For more information about Spitzer,
Alan Buis 818-354-0474
Jet Propulsion Laboratory, Pasadena, Calif.
Alan.buis@jpl.nasa.gov
J.D. Harrington 202-358-0321
Headquarters, Washington
j.d.harrington@nasa.gov
NASA
Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com
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