Cartwheel Galaxy Makes Waves in New NASA Image (Forwarded)
- From: Andrew Yee <ayee@xxxxxxxxxxxxxxxxxxxxxx>
- Date: Fri, 13 Jan 2006 10:21:59 -0500 (EST)
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Image Advisory: 2006-005
January 11, 2006
Cartwheel Galaxy Makes Waves in New NASA Image
A new image from NASA's Galaxy Evolution Explorer completes a
multi-wavelength, neon-colored portrait of the enormous Cartwheel galaxy
after a smaller galaxy plunged through it, triggering ripples of sudden,
brief star formation.
The false-color composite image, available at
http://www.galex.caltech.edu/ , shows the Cartwheel galaxy as seen by
Galaxy Evolution Explorer in ultraviolet light (blue); the Hubble Space
Telescope in visible light (green); the Spitzer Space Telescope in
infrared (red); and the Chandra X-ray Observatory (purple).
"The dramatic plunge has left the Cartwheel galaxy with a crisp, bright
ring around a zone of relative calm," said astronomer Phil Appleton of the
California Institute of Technology, Pasadena, Calif. "Usually a galaxy is
brighter toward the center, but the ultraviolet view indicates the
collision actually smoothed out the interior of the galaxy, concentrating
older stars and dust into the inner regions. It's like the calm after the
storm of star formation." The outer ring, which is bigger than the entire
Milky Way galaxy, appears blue and violet in the image.
Recently-observed features include concentric rings rippling out from the
impact area in a series of star formation waves, ending in the outermost
ring. "It's like dropping a stone into a pond, only in this case, the pond
is the galaxy, and the wave is the compression of gas," said Appleton.
"Each wave represents a burst of star formation, with the youngest stars
found in the outer ring."
Previously, scientists believed the ring marked the outermost edge of the
galaxy, but the latest Galaxy Evolution Explorer observations detect a
faint disk, not visible in this image, that extends to twice the diameter
of the ring. This means the Cartwheel is a monstrous 2.5 times the size of
the Milky Way.
Most galaxies have only one or two bright X-ray sources, usually
associated with gas falling onto a black hole from a companion star. The
Cartwheel has a dozen. Appleton said that makes sense, because black holes
thrive in areas where massive stars are forming and dying fast.
The Cartwheel galaxy is one of the brightest ultraviolet energy sources in
the local universe. In some visible-light images, it appears to have
spokes. Appleton is presenting his finding today at the 207th meeting of
the American Astronomical Society in Washington. His research
collaborators included Armando Gil de Paz of Universidad Complutense,
Madrid, Spain; and Barry Madore of The Observatories of the Carnegie
Institution of Washington, Pasadena, Calif. The team's observations were a
follow-up to studies made by the Galaxy Evolution Explorer science team's
Nearby Galaxy Survey.
Additional information about Galaxy Evolution Explorer is online at
http://www.galex.caltech.edu/
Caltech leads the Galaxy Evolution Explorer mission and is responsible for
science operations and data analysis. NASA's Jet Propulsion Laboratory,
Pasadena, Calif., 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
international partners in the mission.
.
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