Astronomers have combined hundreds of thousands of Spitzer Space Telescope images into a map of the whole Large Magellanic Cloud. They see features throughout the galaxy in such sharp detail that they can count newly formed stars, determine how much dust old stars are pumping into the galaxy and, for the first time, to sensitively map the rate at which stars are forming across an entire galaxy.
“We can use this amazing map to really start to understand in detail how a galaxy evolves,” said Karl Gordon of the University of Arizona Steward Observatory. Gordon heads the UA group who processed 600,000 images that Spitzer’s Multiband Imaging Photometer (MIPS) took of the Large Magellanic Cloud.
The Large Magellanic Cloud, a satellite galaxy of our Milky Way about 160,000 light years away, is an ideal astrophysical laboratory for studying the lifecycle of galaxies.
Using Spitzer’s unprecedented sensitivity across a spectrum of infrared wavelengths, “We now can study some details in another galaxy that so far we’ve been able to study only in our own galaxy,” Gordon said.
Spitzer scientists combined some of the MIPS images with others taken by the Infrared Array Camera (IRAC), a Spitzer instrument that takes images at shorter infrared wavelengths than MIPS does. The result is a composite picture of 300,000 images of the Large Magellanic Cloud, a picture that shows everything from hot stars to cold dust between the stars, or the interstellar medium.
View and download the images at http://www.spitzer.caltech.edu/Media/releases/ssc2006-17/
“What’s exciting and significant is that our images go really deep in the galaxy, deep enough to get a life cycle of the interstellar medium, a life cycle of dust. We see young stars which consume dust as they form in dusty molecular clouds and old stars which are ejecting dust back into the interstellar medium.
“We can now test sophisticated theories about how stars form, how they evolve, what the different populations are, and how important they are in a global galaxy environment,” Gordon said. “One of the strengths of this is not just that we’ve measured a small piece of the galaxy, but we’ve measured almost the entire galaxy in deep, sharp detail.”
The survey of the Large Magellanic Cloud is among 19 key “Legacy” projects undertaken by NASA’s Spitzer Space Telescope, which was launched August 2003. The project is headed by Margaret Meixner of the Space Telescope Science Institute in Baltimore. Others from the UA Steward Observatory who are reporting this research in the Astronomical Journal are Charles W. Engelbracht, Bi-Qing For, Karl Misselt, Jason Harris, Douglas Kelly, Pablo Perez-Gonzalez and Dennis Zaritsky.
Spitzer’s MIPS instruments was developed at The University of Arizona by a team headed by Regents’ Professor George Rieke.
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. Caltech manages JPL for NASA.
CAPTION: What’s Old is New in the Large Magellanic Cloud This vibrant image from NASA’s Spitzer Space Telescope shows the Large Magellanic Cloud, a satellite galaxy to our own Milky Way galaxy.
The infrared image, a mosaic of 300,000 individual tiles, offers astronomers a unique chance to study the lifecycle of stars and dust in a single galaxy. Nearly one million objects are revealed for the first time in this Spitzer view, which represents about a 1,000-fold improvement in sensitivity over previous space-based missions. Most of the new objects are dusty stars of various ages populating the Large Magellanic Cloud; the rest are thought to be background galaxies.
The blue color in the picture, seen most prominently in the central bar, represents starlight from older stars. The chaotic, bright regions outside this bar are filled with hot, massive stars buried in thick blankets of dust. The red color around these bright regions is from dust heated by stars, while the red dots scattered throughout the picture are either dusty, old stars or more distant galaxies. The greenish clouds contain cooler interstellar gas and molecular-sized dust grains illuminated by ambient starlight.
Astronomers say this image allows them to quantify the process by which space dust the same stuff that makes up planets and even people is recycled in a galaxy. The picture shows dust at its three main cosmic hangouts: around the young stars, where it is being consumed (red-tinted, bright clouds); scattered about in the space between stars (greenish clouds); and in expelled shells of material from old stars (randomly-spaced red dots).
The Large Magellanic Cloud, located 160,000 light-years from Earth, is one of a handful of dwarf galaxies that orbit our own Milky Way. It is approximately one-third as wide as the Milky Way, and, if it could be seen in its entirety, would cover the same amount of sky as a grid of about 480 full moons. About one-third of the entire galaxy can be seen in the Spitzer image.
This picture is a composite of infrared light captured by Spitzer. Light with wavelengths of 3.6 (blue) and 8 (green) microns was captured by the telescope’s infrared array camera; 24-micron light (red) was detected by the multiband imaging photometer. (Image credit: NASA/JPL-Caltech/STScI)
