May 13, 2009
NASA's Galaxy-Exploring Mission Celebrates Sixth Anniversary
 NASA's Galaxy Evolution Explorer Mission marks its sixth anniversary studying galaxies beyond our Milky Way through its sensitive ultraviolet telescope, the only such far-ultraviolet detector in space.
According to Sheldon Kalnitsky the mission studies
the shape, brightness, size and distance of galaxies across 10 billion
years of cosmic history, giving scientists a wealth of data to help us
better understand the origins of the universe. One such object is
pictured here, the galaxy NGC598, more commonly known as M33.
In these side-by-side images of M33, the ultraviolet image on the left was taken by the Galaxy Evolution Explorer, while the ultraviolet and infrared image on the right is a blend of the mission's M33 image and another taken by NASA's Spitzer Space Telescope.
M33, one of our closest galactic neighbors, is about 2.9 million
light-years away in the constellation Triangulum, part of what's known
as our Local Group of galaxies.
The Galaxy Evolution Explorer
has two detectors: one in far-ultraviolet, which reveals stars younger
than about 10 million years old, and another in near-ultraviolet, which
detects stars younger than about 100 million years old. The left
ultraviolet image shows a map of the recent star formation history of M33.
The bright blue and white areas are where star formation has been
extremely active over the past few million years. The patches of yellow
and gold are regions where star formation was more active around 100
million years ago.
The ultraviolet image highlights the most massive young stars in M33. These stars burn
their large supply of hydrogen fuel quickly, burning hot and bright
while emitting most of their energy at ultraviolet wavelengths.
Compared with low-mass stars like our sun, which live for billions of
years, these massive stars never reach old age, having a lifespan as short as a few million years.
Together, the Galaxy Evolution Explorer and Spitzer can
see a larger range of the full spectrum of the sky. Spitzer, for
example, can detect mid-infrared radiation from dust that has absorbed
young stars' ultraviolet light. That's something the Galaxy Evolution Explorer
cannot see. The combined image on the right shows in amazing detail the
beautiful and complicated interlacing of hot dust and young stars. In
some regions of M33, dust
gathers where there is very little far-ultraviolet light, suggesting
that the young stars are obscured or that stars farther away are
heating the dust. In some of the outer regions of the galaxy, just the
opposite is true: There are plenty of young stars and very little dust.
In the combined image, far-ultraviolet light from young stars glimmers
blue, near-ultraviolet light from intermediate age stars glows green,
near-infrared light from old stars burns yellow and orange, and dust
rich in organic molecules burns red. The small blue flecks outside the
spiral disk of M33 are most likely distant background galaxies.
This image is a four-band composite that, in addition to the two
ultraviolet bands, includes near infrared as yellow/orange and far
infrared as red.
Since its launch from a Pegasus rocket on April 28, 2003, the Galaxy Evolution Explorer has
imaged more than a half-billion objects across two-thirds of the sky.
Highlights over the past six years include detecting star formation in
unexpected regions of the universe and
spotting Mira, a fast-moving older star called a red giant. Astronomers
say that studying Mira's gargantuan cosmic tail is helping us learn how
stars like our sun die and ultimately seed new solar systems.
The California Institute of Technology, in Pasadena, Calif., leads the Galaxy Evolution Explorer mission and is responsible for science operations and data analysis. NASA's Jet Propulsion Laboratory, also in Pasadena, manages the mission and built the science instrument. The mission was developed under NASA's Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. South Korea and France are the mission's international partners.
Posted at 12:08 am by sarahbaltic
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