Spitzer captures stellar coming of age in our galaxy

The image, which depicts an area of sky 120 degrees wide by two degrees tall was unveiled at the 212th meeting of the American Astronomical Society in St. Louis, Mo.
"This is the highest-resolution, largest, most sensitive infrared picture ever taken of our Milky Way," said Sean Carey of NASA's Spitzer Science Center at the California Institute of Technology, Pasadena, Calif. Carey is lead investigator for one of two teams responsible for the new picture. "Where previous surveys saw a single source of light, we now see a cluster of stars. With this data, we can learn how massive stars form, map galactic spiral arms and make a better estimate of our galaxy's star-formation rate," Carey explained.

"I suspect that Spitzer's view of the galaxy is the best that we'll have for the foreseeable future. There is currently no mission planned that has both a wide field of view and the sensitivity needed to probe the Milky Way at these infrared wavelengths," said Barbara Whitney of the Space Science Institute, Madison, Wis. Whitney is a member of the second astronomy team.

Because Earth sits inside our dusty, flat, disk-shaped Milky Way, we have an edge-on view of our galactic home. We see the Milky Way as a blurry, narrow band of light that stretches almost completely across the sky. With Spitzer's dust-piercing infrared eyes, astronomers peered 60,000 light-years away into this fuzzy band, called the galactic plane, and saw all the way to the other side of the galaxy.

The result is a cosmic tapestry depicting an epic coming-of-age tale for stars. Areas hosting stellar embryos are identified by swaths of green, which are organic molecules, called polycyclic aromatic hydrocarbons, illuminated by light from nearby newborn stars. On Earth, these molecules are found in automobile exhaust and charred barbeque grills, essentially anywhere carbon molecules are burned incompletely.

The regions where young stars reside are revealed as "bubbles," or curved ridges in the green clouds. These bubbles are carved by the winds from young starlets blowing away their natal dust. The starlets appear as yellow and red dots, and the wisps of red that fill most bubbles are composed of graphite dust particles, similar to very small pieces of pencil lead.

Credit: NASA/JPL-Caltech/Univ. of Wisconsin.
High resolution images.

In this mosaic the galactic plane is broken up into five components: the far-left side of the plane (top image); the area just left of the galactic center (second to top); galactic center (middle); the area to the right of galactic center (second to bottom); and the far-right side of the plane (bottom). From Earth, the top two panels are visible to the northern hemisphere, and the bottom two images to the southern hemisphere. Together, these panels represent more than 50 percent of our entire Milky Way galaxy.

The swaths of green represent organic molecules, called polycyclic aromatic hydrocarbons, which are illuminated by light from nearby star formation, while the thermal emission, or heat, from warm dust is rendered in red. Star-forming regions appear as swirls of red and yellow, where the warm dust overlaps with the glowing organic molecules. The blue specks sprinkled throughout the photograph are Milky Way stars. The bluish-white haze that hovers heavily in the middle panel is starlight from the older stellar population towards the center of the galaxy.

This is a three-color composite that shows infrared observations from two Spitzer instruments. Blue represents 3.6-micron light and green shows light of 8 microns, both captured by Spitzer's infrared array camera. Red is 24-micron light detected by Spitzer's multiband imaging photometer.

The Galactic Legacy Infrared Mid-Plane Survey Extraordinaire team (GLIMPSE) used the telescope's infrared array camera to see light from newborn stars, old stars and polycyclic aromatic hydrocarbons. A second group, the Multiband Imaging Photometer for Spitzer Galactic Plane Survey team (MIPSGAL), imaged dust in the inner galaxy with Spitzer's multiband imaging photometer.



Credit: NASA/JPL-Caltech/Univ. of Wisconsin.
High resolution images.

In this mosaic the galactic plane is broken up into five components: the far-left side of the plane (top image); the area just left of the galactic center (second to top); galactic center (middle); the area to the right of galactic center (second to bottom); and the far-right side of the plane (bottom). Together, these panels represent more than 50 percent of our entire Milky Way galaxy.

The red haze that permeates the picture comes from organic molecules called polycyclic aromatic hydrocarbons, which are illuminated by light from massive baby stars. On Earth, these molecules are found in automobile exhaust, or charred barbeque grills -- anywhere carbon molecules are burned incompletely.

The patches of black are dense, obscuring dust clouds impenetrable by even Spitzer's super-sensitive infrared eyes. Bright arcs of white throughout the image are massive stellar incubators. The bluish-white haze that hovers heavily in the middle panel is starlight from the older stellar population towards the center of the galaxy.

This picture was taken with Spitzer's infrared array camera, as part of the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) project. This is a four-color composite where blue is 3.6-micron light, green is 4.5 microns, orange is 5.8 microns and red is 8.0 microns.

Blue specks sprinkled throughout the photograph are individual older Milky Way stars. The bluish-white haze that hovers heavily in the middle two panels is starlight from the galaxy's older stellar population. A deep, careful examination of the image also shows the dusty remnants of dying and dead stars as translucent orange spheres.

"With these Spitzer data, we've been able to catalogue more than 100 million stars," said Edward Churchwell of the University of Wisconsin, at Madison. Churchwell is principal investigator of one of the teams.

"This picture shows us that our Milky Way galaxy is a crowded and dynamic place. We have a lot to learn. I've definitely found a lot of things in this map that I didn't expect to see," said Carey.

This infrared composite incorporates observations from two Spitzer instruments. Data from the infrared array camera were collected and processed by The Galactic Legacy Infrared Mid-Plane Survey Extraordinaire team, led by Churchwell. The Multiband Imaging Photometer for Spitzer Galactic Plane Survey Legacy team, led by Carey, processed observations from Spitzer's multiband imaging photometer. Blue represents 3.6-micron light, green shows light of 8 microns and red is 24-micron light.

Source: Jet Propulsion Laboratory
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