Galaxies are perhaps one of the most attractive deep-sky objects to observe and photograph. They represent massive collections of dust, gas
and countless billions of stars and are best described as islands of space matter across the universe. They are characterized as being either
spiral or elliptical in nature and usually have a bright central core. Equally stunning to observe (with large-aperture telescopes) and image
are galaxy clusters which represent collections of gravitationally-bound groups of galaxies whose members number from tens to thousands and
which are classified on the basis of their richness (ie. number of galaxy members), shape (spherical, flat or irregular) and content (spiral
or elliptical). Charles Messier's list of deep-sky celestial gems includes approximately forty bright and large galaxies.
Our own galaxy, the Milky Way, represents a galaxy within the Local Group (of Galaxies)
numbering 30 galaxies in total, five million light years in diameter and which is moving in unison towards the constellation of Virgo. Other
prominent galaxies within the Local Group include Andromeda (150,000 light-years in diameter), Triangulum (40,000 light-years in diameter) and
the Large and Small Magellanic Clouds (30,000 and 20,000 light-years in diameter respectively). The center of the Local Group is believed to
lie between the Milky Way and the Andromeda Galaxy. The richest member of our Local Group is the Virgo Cluster which is believed to contain
approximately 2500 galaxies mostly elliptical in nature.
Note: One of the most stunning and brightest galaxies of the northern hemisphere is M81, a classic grand design
spiral galaxy with uniform swirling arms which measures two-thirds of the full-moon in diameter and lies 11.8 million light-years away in the
circumpolar constellation of Ursa Major. The galaxy was first discovered by Johann Elert Bode on the last day of the year in 1774 along with
its companion galaxy M82 which lies 150,000 light-years and 0.75 degrees away (both galaxies are interacting). It is estimated that M81 is
comprised of approximately 250 billion stars including many young blue hot stars in its spiral arms (star-forming regions) as well as older
yellow stars in its core. This galaxy has been the source of one (type II) supernova discovery (1993J, mag 10.5); over 30 Cepheids have been
identified and measured; and it is believed that approximately 200 globular clusters are home to M81. The galaxy is best observed during
winter when M81 (and UMa) cross the meridian just after midnight and is easily visible in 10x50 binoculars and low-power magnifications
through a telescope.
Please click on the image below to display in higher resolution (1200 x 900)