M81 and Holmberg IX | Rod Pommier

Photographer
Rod Pommier
Email
pommierr@ohsu.edu
Location of photo
Pommier Observatory, Portland, Oregon, USA
Date/Time of photo
2013-10-06 through 2013-10-10
Equipment
Telescope/Mount: Celestron Compustar C14 with Astrophysics 0.75x focal reducer (f/8.3). Camera: SBIG STL 11000M with Baader Planetarium LRGB filters. Location: Pommier Observatory, Portland, OR, USA. Exposures:L:R:G:B=430:70:70:70=10 hours, 40 minutes total exposure.
Description
M81 is a class Sb spiral lying 11.8 million light-years away. It is a classic grand design spiral with a central bulge of old population II yellow stars and two major spiral arms of hot blue population I stars. Despite this classic appearance, it exhibits changes hinting at a recent disruptive interaction: the aberrant parallel dust lanes cutting across its disk, to the lower left of the nucleus. The responsible interaction likely occurred with M82, which appears far more disrupted. The dwarf irregular galaxy Holmberg IX to the right is a satellite analogous to one of the Milky Way's Magellanic clouds.