November 2021
The Backyard Astronomer
by
Adam England

M33, The Triangulum Galaxy

In the same patch of sky as Andromeda is possibly the most distant object one can see with the naked eye. In good viewing conditions, with 20/20 vision and without magnification, you may be able to spot the Triangulum Galaxy, or Messier 33. It is sometimes referred to as the Pinwheel Galaxy, however another galaxy is recorded in separate astronomical databases as the Pinwheel, and so, to prevent confusion, we will stick with Triangulum, so named based on the simple triangle its three main stars form. While certainly one of the smallest and simplest of the 48 Ptolemaic constellations, it is a great place to look for deep-sky objects.

The Babylonians referred to this formation of stars as The Plough and recorded it on clay tablets dating back nearly 3,000 years, making it possibly the oldest documented constellation. (This is not to be confused with the UK nickname for Ursa Major, which we usually call the Big Dipper and they call The Plough.) In ancient times this constellation would have risen early in the predawn hours in early spring, signifying the time for the farmers of the Fertile Crescent to begin plowing their fields. The Greeks referred to it as Deltoton for its resemblance to the Greek letter delta, a shape also referenced where the Nile River empties into the Mediterranean, the Nile delta. The Romans had a few names for this triad, one of which was Sicilia, for the roughly triangular shape of the island of Sicily. Roman mythology stated that Ceres, the island’s patron goddess, begged the god Jupiter to place it in the heavens, and so the triangle in the sky came to be. Other names used by ancient Mediterranean cultures almost universally reference the tri- prefix we associate with the number three, including Tricuspis, Triquetrum, Trigonon, Trigonum and eventually Triangulum. The modern International Astronomical Union, which regulates the accepted names of astronomical bodies and objects, assigned the abbreviation “Tri” to this constellation in 1922.

While much smaller than its neighbor, with an apparent size of 70.8 x 41.7arcminutes, we view the Triangulum Galaxy nearly face-on, and as such we can see its features much more clearly defined. It has prominent arms of dust, gas, and stars spiraling out from its center, but it differs from the Milky Way and Andromeda on one major feature, in that it does not have a bulge at its center. Surveys of the galactic center of M33 show the stars there orbit normally, suggesting that it does not have a supermassive black hole like its two larger neighbor sin the Local Group. The future may yet provide it with such a blackhole, as a major collision with either Andromeda, the Milky Way or both is expected to combine all three galaxies into one mega-galaxy in about 2.5 billion years.

If you found Andromeda last month, you’re on the right path. You used the bright star Alpheratz to star hop across the stream of stars to its left. The second star in the stream is Mirach, and the Triangulum Galaxy is approximately the same distance below it as Andromeda is above it. Since it is face-on, the brightness of its stars seems spread over a much larger area, so it can be tough to find the first time with your binoculars or small scope. Look for a fuzzy spot, almost like a smudge on a window, then adjust your focus and play with different eyepieces to resolve more detail.

If you would like to learn more about the sky, telescopes, or socialize with other amateur astronomers, visit us at prescottastronomyclub.org or Facebook @PrescottAstronomyClub to find the next star party, Star Talk, or event.

Adam England is the owner of Manzanita Financial and moonlights as an amateur astronomer, writer, and interplanetary conquest consultant. Follow his rants and exploits on Twitter @AZSalesman or at Facebook.com/insuredbyadam.