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ASTRONOMY
New Observations Illuminate
the Middle of the Milky Way
Image:NASA/University of Massachusetts/D.Wang et
al. |
Located 26,000 light years away from Earth and surrounded by clouds of
dust, the center of the Milky Way galaxy is a hard thing for scientists to
get a good look at. In fact, for nearly 20 years astronomers have been
wondering about the origin of x-rays seen emanating from the core of our
galaxy. Originally it was unclear whether the radiation came from widely
dispersed hot interstellar gas or from multiple individual sources. Now
new research suggests that it may be a combination of both. According to a
report published today in the journal Nature, some of the emissions
come from discrete sources representing hundreds of never-before-seen
white dwarf stars, neutron stars and black holes.
Using data from the Chandra X-ray Observatory, Q. Daniel Wang of the
University of Massachusetts, Amherst, and colleagues identified nearly
1,000 point-like sources that contribute to the x-ray emission, only 20 of
which were previously known. Focusing on the spectral features associated
with the presence of iron in the central galaxy, the team determined that
the majority of the emissions from highly ionized iron can be attributed
to discrete sources. Specifically, the most energetic iron emission they
studied is characteristic of so-called x-ray binary stars—duos comprised
of a dense stellar object such as a white dwarf star, a neutron star or a
black hole that collects matter from a less dense companion, emitting
x-rays in the process. The classification of these new sources of x-rays
has allowed the scientists to revise their temperature estimates of the
interstellar gas: according to study co-author Eric Gotthelf of Columbia
University, the gas appears to be a mere 10 million degrees, 10 times
cooler than previously thought.
The celestial survey also found large amounts of diffuse x-ray-
emitting material distributed assymetrically around the Galatic Center.
Together, the new findings provide the most detailed x-ray map yet of
objects near the middle of the Milky Way. "A detailed picture of the
physical processes that influence this extraordinary region is key to
understanding all other galactic nuclei in the universe," Andreas Eckart
of the University of Cologne in Germany writes in an accompanying
commentary. These results, he further notes, "finally settle important
aspects of the twenty-year-old debate surrounding the origin of x-ray
emission from the Galactic Center." —Sarah Graham
RELATED LINKS:
The
Milky Way's Hidden Black Hole
Probing the Galactic
Core
Galaxies
Behind the Milky Way
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