Western Slope Skies - Late Summer Galaxies

Aug 23, 2019

Credit NOAO/AURA/NSF Local Group Survey Team and T.A. Rector

When hot summer days yield to cool, pleasant nights, late summer evenings provide some of the best opportunities for star gazing. The constellations of summer and early autumn contain some of the finest examples of the various types of astronomical objects.

Of course, chief among these is our own Milky Way Galaxy, which dominates the sky. In late summer, we look in the southwest toward the center of our galaxy, which is dense with stars. Readily apparent is the Great Rift, which appears to separate our galaxy into two distinct parts. This is merely the result of the gas and dust, common in spiral galaxies, which obscures the stars beyond.

Astronomers refer to spring as galaxy season, because during spring we are peering up from the plane of our Galaxy, so distant galaxies are not hidden by the gas and dust within our own Milky Way. But several of the closest, and therefore most magnificent, galaxies are on view now in late summer. Rising in the east is the Great Andromeda Galaxy which, from a dark location, appears as a broken off piece of the Milky Way, larger than the full Moon. In amateur telescopes two satellite galaxies are also easily visible.

In the early morning hours another galaxy, Messier 33, rises in the east. From a very dark location, this galaxy is at the limit of naked eye visibility.

Looking northwest most people can recognize the Big Dipper, an asterism which is part of the constellation Ursa Major, or Great Bear. Two of the stars in the dipper’s bowl point to Messier 81, perhaps the third brightest galaxy visible from the northern hemisphere, but beyond naked eye visibility. Through even a small telescope at low power, however, not only does M81 show hints of its round, spiral shape, but also that it is accompanied by another galaxy, M82, to which it is gravitationally bound. And not far below Alkaid, the star at the end of the handle of the Big Dipper, is another magnificent object: a face-on spiral known as M51, the Whirlpool Galaxy, in the constellation Canes Venatici. M51 also appears accompanied by another galaxy.

Western Slope Skies is produced by the Black Canyon Astronomical Society. This episode was written and recorded Bernie Forman.