Dark starry nights this week - hopefully clouds will cooperate- bring the beauty of autumn skies to your backyard. Constellations marking autumn evenings are generally dim, but should be no less fascinating. The Milky Way Band continues to arc across the heavens, but the wider and more prominent portion seen due south in summer is now receding into the west. Remember, this hazy band, which looks somewhat like a smoke trail from some grand wood stove, is the cross-section of our flat Milky Way Galaxy of which we are a part. Our spiral galaxy has a prominent, fatter hub in the middle, from which the spiral arms extend. The bright and glorious hub is better seen from deep south, especially below the Earth’s equator. From mid-northern latitudes such as in Pennsylvania, the hub is only partly seen, and is low on the south horizon on summer evenings. By the time of mid-autumn, the region of the galactic hub is already below the southwestern horizon at night fall. This leaves us the narrower and slightly dimmer Milky Way Band, stretching around the sky. You need a clear, moonless night to see it, away from town and shopping plaza lights. The most easily visible neighboring galaxy is now well seen in the evening. The Great Andromeda Galaxy, also known as M31, is one of the closest galaxies to our own and is part of what is called the “Local Group,” an assembly of galaxies in this neighborhood of the Universe which travel together, bound by one another’s gravity. On the next clear, dark night, have a look yourself. M31 appears as an elliptical, hazy smudge, quite dim but readily seen once you know what to expect and where to look. Binoculars will help you a great deal. With them you will more easily discern the elliptical shape and see that the center is brighter. The galaxy is really round like a dinner plate but it appears elliptical due to the angle from which we are situated- the flat circle becomes foreshortened. To locate M31, face northeast at around 9 p.m. or so (in October), and look about three-quarters the way up. Find the bright “M” shaped constellation of Cassiopeia, not quite overhead. The “M” at this time appears on its side. Look to the right of the top right corner star of the “M”, about the same distance as the “M” is tall (as seen in this orientation). This brings you to the dim fuzzy spot which is the Andromeda Galaxy. If you don’t see it immediately, keep scanning the immediate area until you do. Once found it is unmistakable. Then see if you can find it with unaided eyes alone. Now stop and realize you are seeing an entire galaxy beyond our own Milky Way. It is calculated to be approximately 2.5 million light years away and as much as 260,000 light years wide. Very similar to the Milky Way, astronomers learn much about our own galactic home by studying its big, close neighbor. Look for brilliant Jupiter after about 10 p.m., rising in the northeast. Last Quarter Moon is on Monday, October 8. Send your notes to email@example.com. Keep looking up!
LOOKING UP: Find the Andromeda Galaxy