Here is an update on the things astronomers are learning from the Spitzer Infrared Nearby Galaxy Survey, which is currently underway. The above image is a composite if the the "Cigar galaxy," Messier 82. On the left is a visible-light image from the National Optical Astronomy Observatory. On the right is a "smokin'" infrared image from NASA's Spitzer Space Telescope.
The visible-light picture of Messier 82, shows only a bar of light against a dark patch of space. Longer exposures of the galaxy have revealed cone-shaped clouds of hot gas above and below the galaxy's plane. It took Spitzer's three sensitive instruments to show that the galaxy is also surrounded by a huge, hidden halo of smoky dust (red in infrared image).
Of those instruments, Spitzer's infrared spectrograph told astronomers that the dust contains a carbon-containing compound, called polycyclic aromatic hydrocarbon. This smoky molecule can be found on Earth in tailpipes, barbecue pits and other places where combustion reactions have occurred.
Messier 82 is located about 12 million light-years away in the Ursa Major constellation. It is viewed from its side, or edge on, so it appears as a thin cigar-shaped bar. The galaxy is termed a starburst because its shrouded core is a fiery hotbed of stellar birth. A larger nearby galaxy, called Messier 81, is gravitationally interacting with Messier 82, prodding it into producing the new stars.
The infrared image was taken by Spitzer's infrared array camera as a part of the Spitzer Infrared Nearby Galaxy Survey. Blue indicates infrared light of 3.6 microns, green corresponds to 4.5 microns, and red to 5.8 and 8.0 microns. The contribution from starlight (measured at 3.6 microns) has been subtracted from the 5.8- and 8-micron images to enhance the visibility of the dust features.
You can read more and see more images at the article URL: www.jpl.nasa.gov/spaceimages/details.php?id=PIA02917
The visible-light picture is from the National Optical Astronomy Observatory, Tucson, Arizona. To learn more, visit the observatory home page: noao.edu
The Spitzer Space Telescope (SST) operations are extended through Fiscal year 2014 with closeout planned for Fiscal year 2015. Launched August 2003 aboard a Delta II rocket, Spitzer Space Telescope is an infrared space observatory, the fourth and final of the NASA Great Observatories program. The observatory was renamed in honor of Lyman Spitzer, one of the 20th century's great scientists. The mission website is: http://www.spitzer.caltech.edu/