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Spiral galaxy M81 in Ursa Major
auteur: R.Jay GaBany/Novapix
référence: a-gax30-31012
Image Size 300 DPI: 34 * 34 cm
Located about 12 million light-years from our planet, M81 (NGC 3031) together with M82 (NGC 3034), NGC 3077 and NGC 2976 forms one of the most iconic groups of interacting galaxies. The M81 group has also been the subject of many studies searching for and analyzing evidence of strong interactions among its components. In 1965, Halton Arp detected an unusual looping feature near M81 while examining photographic plates produced with the 48-inch Schmidt on Mount Palomar. Traditionally, Arp’s loop has been interpreted as a tail resulting from the tidal interaction between M81 and M82. However, since its discovery that explanation has been doubted by many researchers. Interestingly, the region of the sky containing the M81 group of galaxies is filled with Galactic cirrus and Arp’s loop exhibits colors and emission properties similar to those observed in Galactic cirrus clouds.
This optical image suggests that the light observed at optical wavelengths is a combination of emissions from:
recent star forming regions situated near M81,
the extended disk of M81 and
scattered light from the same Galactic cirrus that is responsible for the bulk of the far infrared emissions. Although our observations cannot exclude the presence of some material stripped from the disk of M81 (NGC 3031) and/or M82 (NGC 3034) that is chance located in our line of sight to and far behind this intruiging structure, our findings suggest that Arp's Loop is situated between the observer and M81 (NGC 3031) and represents an optically (relatively) bright concentration of Milky Way galactic cirrus. This 23 hour exposure was produced from a remotely operated observatory in the mountains of south central New Mexico. It was taken through a 20 inch Ritchey-Chretien telescope with an 16-mega pixel camera. February 12- 19, 2010.
Contact : Stéphane Aubin +33-(0)9-51-26-53-76
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