It may be hard to believe in this age of scientific wonders, but barely 100 years ago the best astronomers in the world were debating whether the Milky Way, our home galaxy, might be the entire universe.
The claim seems inconceivable from the lofty perch of our current scientific understanding. We enlightened moderns know the earth is round, that vaccines work, that astrology is bunk, the Bermuda Triangle is just a patch of ocean, the earth is very old, and reports of creatures like Bigfoot and the Loch Ness Monster are products of bad cameras and overactive imaginations, or possibly bad imaginations and overactive cameras. And that the observable universe contains somewhere around two trillion galaxies each more or less like our own Milky Way. We know all that, right? Right?
Suffice it to say that scientific understanding is a work in progress, and probably no one on any side should claim enlightenment just yet.
But there’s an object rising in the north-eastern sky over Millbrook that helps put the scientific debate — and maybe the enlightenment debate, too — in a little more context. That object is the Andromeda Galaxy, also known as “Messier 31” for the collection of faint, fuzzy objects catalogued by the French astronomer Charles Messier in 1781.
In 1920 the astronomers Harlow Shapley and Heber Curtis debated whether Andromeda was a distant galaxy or a local “spiral nebula.” At stake was nothing less than the scale of the universe. Shapley believed that Andromeda was comparatively small and lay wholly within the Milky Way, and calculated that if Andromeda were indeed a galaxy, it would be inconceivably, unacceptably far away. The universe must, he thought, consist of only the Milky Way. Curtis, on the other hand, argued that Andromeda was a self-contained galaxy like our own. He was right, of course, though the question of Andromeda’s distance wasn’t resolved until 2005. That distance is now reliably placed at 2.54 million light years.
Astronomy history aside, Andromeda is a marvel to behold on a hot July night and can be seen using normal binoculars under a dark sky, or with the naked eye under ideal conditions.
There are a few ways to find Andromeda, but it’s easiest, I think, to let the constellation Cassiopeia point the way. Some night in July (I recommend July 10 for the new moon), search the north-eastern sky for a smallish constellation shaped like a lopsided “W.” The lopsided appearance is caused by the distended right half of the “W,” which looks like a triangular arrow. Now imagine a line leading from the tip of the arrow and follow it with your binoculars about halfway to the horizon. There you will see a pale cotton puff floating serenely amid a gossamer halo. In fact, however, Andromeda is a monstrously large galaxy on a collision course and will swallow the Milky Way for a light snack in about 4.5 billion years. Nature!
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Stargazing by Dennis Vanderspek