It’s galaxy season, so you better be careful for any darting out in front of you. Did I mean to say deer season? No, galaxy season. According to prognosticating astronomers, the Andromeda Galaxy is heading right for us and will collide with the Milky Way Galaxy in a number of years.
It’s galaxy season, so you better be careful for any darting out in front of you. Did I mean to say deer season? No, galaxy season. According to prognosticating astronomers, the Andromeda Galaxy is heading right for us and will collide with the Milky Way Galaxy in a number of years. Although discussed in the June Astronomy Magazine as well as many other sources, most haven’t heard of this purported accident waiting to happen. It’s just as well, for there are always some people who get uptight about anything. Also known as M31, the Andromeda spiral galaxy and the Milky Way’s spiral -- with Earth included -- are hurtling toward each other at 270,000 mph (or so). Even at this incredible speed, however, you needn’t stay awake at nights worried over it (but if you do, you may as well get some stargazing in!). Given the immense distance -- 2.5 million light years -- separating the two galaxies, they would not collide until two to five BILLION years from now. As I said, a “number of years.” Of course a lot can happen before then. M31 is the most easily visible galaxy beyond the Milky Way and is visible to the unaided eyes as a fourth magnitude, fuzzy oval. The best time for evening viewing is in the autumn. In early June, you can start to see it about 1 a.m., low in the northeast, but to see anything in the universe more clearly, you should wait for it to rise farther. A dark night is needed, and you need a spot where light pollution isn’t a problem in that direction. Binoculars will give a better view. It is a wonder to realize that even as you gaze at M31, it is gaining in brightness as it is coming toward you. Because of the great distance, the brightening is not detectable in anyone’s life span. We call springtime “galaxy season” not because of M31, but because of the vast host of distant galaxies occupying a large part of the evening sky. They make up the “Virgo Cluster,” which actually overlaps a few constellations. This fantastic mass of galaxies travels space together, bound by gravity. Users of even small telescopes can find some of them rather quickly just by slowly scanning the general area where they are most dense, in eastern Virgo and western Leo, two prominent spring constellations. Most of them appear as dim, small fuzzy spots. Long exposure photographs reveal much more. Larger backyard telescopes can pick out spiral structure on a “handful” of galaxies, and many will show a brighter center -- the galactic hub from which the outer spiral arms of stars, cosmic dust and gas extend. Many galaxies are observed in collision. They actually merge. Few stars would actually hit each other but would pass by one another; nebulae (cosmic clouds) do collide and interact. The merger takes a very long time. The results are disheveled, misshapen galaxies, and bursts of star formation as nebulae are compressed. Some stars are thrown out into long, curving tails formed by tidal forces. Can you imagine how starry the sky would be? The Milky Way is part of a small galaxy cluster as well, called the “Local Group.” Our “neighborhood” includes more than 30 galaxies, several of them being small satellites of larger ones. The Milky Way is one of the three largest in the group, the others being M31 and another spiral galaxy, M33, easily seen with binoculars in the autumn evening sky. M31 is the largest; the Milky Way comes in second. We have several small satellite galaxies orbiting the Milky Way. Only two are visible to unaided eyes -- the Large and Small Magellanic Clouds. Too bad for Northerners, they are only visible from far southern latitudes. Astronomers deduce the relative motion of M31 and other galaxies by the shifting of lines in the galaxy light’s spectrum of colors. These lines denote elements making up the billions of stars in the galaxy, mostly due to hydrogen. M31’s spectral lines are shifted toward the blue end of the spectrum, meaning it is coming toward us. Most galaxies are speeding away from us and are red-shifted. The shifting is caused by the “Doppler effect,” which also applies to the shifting frequency of sound that you hear as a vehicle with a bad muffler races past you breaking the speed limit with hopefully a police car behind it. The noise of the engine rises and falls in pitch as it goes by. New moon is June 3. Keep looking up! Peter W. Becker is managing editor at The Wayne Independent in Honesdale, Pa. He has been an amateur astronomer since the age of 12, in 1969. He may be reached at email@example.com.