Credit: NASA/JPL-Caltech/K. Gordon (University of Arizona)

Messier 81

The magnificent and dusty spiral arms of the nearby galaxy Messier 81 are highlighted in these NASA Spitzer Space Telescope images. Located in the northern constellation of Ursa Major (which also includes the Big Dipper), this galaxy is easily visible through binoculars or a small telescope. M81 is located at a distance of 12 million light-years.

The three-panel mosaic is a series of images obtained with the multiband imaging photometer. Thermal infrared emission at 24 microns (top), 70 microns (center) and 160 microns (bottom) is shown in the images. Note that the effective spatial resolution degrades as ones moves to longer wavelengths.

At these wavelengths, Spitzer sees the dust, rather than the stars, within the disc of silicates and carbonaceous grains. It is well-mixed with gas, which is best seen at radio wavelengths, to form the essential ingredients for future star formation.

About the Object	Object Name: Messier 81 (NGC 3031; UGC 5318) Object Type: Spiral galaxy Position (J2000): RA: 09h55m33.2s DEC +69d03m55s Distance: 12,000,000 light-years (3.6 Mpc) Magnitude: 7.9 Constellation: Ursa Major (the Big Bear)
About the Data	Image Credit: NASA/JPL-Caltech/K. Gordon (University of Arizona) Instrument used: MIPS Wavelengths: 24, 70 and 160 microns Exposure date: November 24, 2003 Exposure times:     80 seconds per position (24 microns)     40 seconds per position (70 microns)     8 seconds per position (160 microns) Image Size: 23.3 x 17.8 arcmin Orientation: North is rotated 91 degrees clockwise from the vertical Release Date: December 18, 2003
Observers	Karl D. Gordon, Principal Investigator (University of Arizona) Steven P. Willner, Principal Investigator (Harvard-Smithsonian Center for Astrophysics) Almudena Alonso-Herroro (University of Arizona) Philip Appleton (SSC/Caltech) Matthew L. N. Ashby (Harvard-Smithsonian Center for Astrophysics) Pauline Barmby (Harvard-Smithsonian Center for Astrophysics) Chad Engelbracht (University of Arizona) Giovanni G. Fazio (Harvard-Smithsonian Center for Astrophysics) David Frayer (SSC/Caltech) George Helou (SSC/Caltech) Joannah Hinz (University of Arizona) Robert Kennicutt (University of Arizona) Karl Misselt (University of Arizona) Michael A. Pahre (Harvard-Smithsonian Center for Astrophysics) Pablo Perez-Gonzalez (University of Arizona) George Rieke (University of Arizona) Marcia Rieke (University of Arizona) Susan Stolovy (SSC/Caltech) Lisa Storrie-Lombardi (SSC/Caltech)

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