structure, which spans 50,000 light-years and is positioned in
the center of the Milky Way, was identified by NASA's
Fermi Gamma-ray Space Telescope.
Finkbeiner, founder of the new structure and an astronomer at the
Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., has
discovered two gamma-ray-emitting bubbles that may be millions of
years old and span from the constellation Virgo to the constellation
Grus. He was able to find these bubbles using NASA's Fermi Gamma-ray
Space Telescope, which is a space observatory, and
astrophysics/particle physics partnership developed in collaboration
with the U.S. Department of
we see are two gamma-ray-emitting bubbles that extend 25,000
light-years north and south of the galactic center," said
Finkbeiner. "We don't fully understand their nature or origin."
hints of the bubbles were visible in earlier spacecraft
data, astronomers conducting previous studies on gamma rays were
unable to find the bubbles mainly because of the fog which surrounds
gamma rays throughout the sky. When particles, which are moving at
the speed of light, react with light and interstellar gas in the
Milky Way, a fog develops.
and his team were able to find the gamma-ray-emitting bubbles by
processing available data from Fermi's Large Area Telescope (LAT),
which is a high-resolution and extremely sensitive gamma-ray
detector. Researchers continuously refined models in an effort to
identify new gamma-ray structures hidden by the fog. Finkbeiner was
able to isolate the fog from the LAT data by using different
estimates of the fog in these models, and finally stumbled upon the
its launch in June 2008, Fermi repeatedly has proven itself to be a
frontier facility, giving
us new insights ranging from the nature of space-time to the
first observations of a gamma-ray nova," said Jon Morse,
Astrophysics Division director at NASA Headquarters in Washington.
"These latest discoveries continue to demonstrate Fermi's
next step is to figure out how these bubbles were formed. The
gamma-ray-emitting bubbles have "well-defined" edges and
their emissions are much more energetic than any other gamma-ray fog
previously found in the Milky Way, which, according to researchers,
suggests that the bubbles were formed as a result of large and
energy release. Finkbeiner and his team are unsure as to what the
source of this energy release was, but hypothesize that it may be a
particle jet from the supermassive black hole located at the galactic
center. There is no evidence that the Milky Way's black hole has
these fast particle jets, but there's a possibility it may have in
the past. Another possible source of the energy release may be
gas outflows from a burst of star formation.
other galaxies, we see that starbursts can drive enormous gas
outflows," David Spergel, a scientist at Princeton
University. "Whatever the energy source behind these huge
bubbles may be, it is connected to many deep questions in
addition to discovering the gamma-ray-emitting bubbles, the team also
revealed Fermi's best picture of the gamma-ray sky on Tuesday. They
were able to produce such an image after two years of data
scans the entire sky every three hours, and as the mission continues
and our exposure deepens, we see the extreme universe in
progressively greater detail," said Julie McEnery, Fermi project
scientist at NASA's
Goddard Space Flight Center in Greenbelt, Maryland.
quote: Finkbeiner was able to isolate the fog from the LAT data by using different estimates of the fog in these models, and finally stumbled upon the large bubbles.