Spitzer Captures Our Galaxy's Bustling Center
A new infrared mosaic from NASA's Spitzer Space Telescope offers a stunning view
of the stellar hustle and bustle that takes place at our Milky Way galaxy's center.
The picture shows throngs of mostly old stars, on the order of hundreds of thousands,
amid fantastically detailed clouds of glowing dust lit up by younger, massive stars.
Image right: This infrared image from Spitzer shows hundreds of thousands of stars crowded into the swirling core of our spiral Milky Way galaxy. In this false-color picture, old and cool stars are blue, while dust features lit up by blazing hot, massive stars are shown in a reddish hue. Both bright and dark filamentary clouds can be seen, many of which harbor stellar nurseries. The plane of the Milky Way's flat disk is apparent as the main, horizontal band of clouds. Image credit: NASA/JPL-Caltech
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"With Spitzer, we can peer right into the heart of our own galaxy and see breathtaking
detail," said Dr. Susan Stolovy of the Spitzer Science Center at the California Institute
of Technology in Pasadena. "This picture is crammed with fascinating features that
we have just begun to explore."
The image is available online at http://www.spitzer.caltech.edu/spitzer
The Milky Way's core is indeed a very busy place. Stars are packed together like subway
riders as they race around the supermassive black hole that lies at the center. Our sun is
located 26,000 light-years away in a more peaceful, spacious neighborhood, out in the galactic
suburbs. It circles the galaxy about every 225 million years, which amounts to 20 trips over the
course of its 4.5-billion-year lifetime. In contrast, stars at the galactic center complete one
lap in only a few million years or less.
"One question we hope to address is how stars can form so efficiently in a place like the galactic
center," said Stolovy. "Stars there are still able to form in an environment with unusually strong
magnetic fields and tidal shear forces."
Viewing the center of the Milky Way from Earth can be difficult because the plane of the galaxy's
spiral disk is filled with cold dust. Visible light coming from this distant region is virtually
impossible to observe because dust dims it by a factor of one trillion. But infrared light can
shine through this dust. The infrared light in this Spitzer view has wavelengths about 10 times
longer than what the human eye can see, and is dimmed only about four times.
This infrared advantage, combined with Spitzer's superb image quality, has resulted in the deepest
and sharpest view yet of an expansive stretch of the galactic center. The pictured region, located
in the Sagittarius constellation, is 900 light-years across. It covers the same area on the sky
that a grid of four by three full moons would occupy.
Features within the new mosaic include dust clouds of a dizzying variety, such as glowing filaments,
wind-blown lobes flapping outward from the plane of the galaxy, and finger-like pillars. The Spitzer
image also shows newborn stars just beginning to break out of their dark and dusty cocoons, and exquisitely
detailed dark clouds so dense they are opaque even in infrared wavelengths. Some of these features are
located near the physical center of our galaxy, while others lie closer to Earth.
"Our Spitzer data, combined with data obtained by other telescopes, will allow us to determine which of
these objects are truly at the galactic center, and which are in spiral arms along the way," said Stolovy.
"This survey will help us to better understand the mass distribution and structure of our own galaxy and
how it compares to other galaxies."
Stolovy and her colleagues are particularly thrilled about the high quality of the Spitzer image
when they remember the challenges they overcame in obtaining it. The galactic center is very bright in
infrared wavelengths, and could have potentially saturated Spitzer's sensitive detectors. The astronomers
solved this problem by taking advantage of Spitzer's ability to take very short exposures. They collected
the thousands of snapshots that make up their final mosaic in just under 16 hours.
The Jet Propulsion Laboratory manages the Spitzer Space Telescope mission for NASA's Science Mission
Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech. JPL is a
division of Caltech. NASA's Goddard Space Flight Center, Greenbelt, Md., built Spitzer's infrared array camera,
which took the new image. The instrument's principal investigator is Dr. Giovanni Fazio of the
Harvard-Smithsonian Center for Astrophysics.
Stolovy presented the image today during the 207th meeting of the American Astronomical Society in
Additional graphics and more information about Spitzer is at http://www.spitzer.caltech.edu/spitzer
For more information about NASA and agency programs on the Web, visit http://www.nasa.gov/home/
Whitney Clavin (818) 354-4673