The Triangulum Galaxy (also known as the Pinwheel Galaxy or M33) is the third largest galaxy in our Local Group of galaxies (after the Milky Way and Andromeda). It is about three million lightyears away from us. Hence we enjoy a better view of it than any other galaxy except Andromeda.
The Triangulum Galaxy (M33) (75 min total exposure Dec 18, 2022)
The most prominent features in M33 are the two mottled inner spiral arms arranged in a backward S. Each arm of the S has a central core of dark dust. The bright central core of the galaxy is not as prominent as it is in many other spiral galaxies.
M33 is about twice as large in the sky as the full moon, but is not visible to the naked eye except from an exceptionally clear and dark sky away from any city lights. Because it is so near, large telescopes can see a number of interesting kinds of objects that are normally only seen within our Milky Way. My 8-inch scope can even spot some of these in a long exposure image, and I’ve noted a few of them:
- NGC 604 is one of the largest emission nebulae known — more than 1,000 times the size of the Orion Nebula in our own galaxy!
- NGC 595 is the second-brightest emission nebula in M33. Like NGC 604 it has a reddish glow due to its hydrogen emissions.
- The NGC 588 and NGC 592 and IC 132 nubulae sport a bluish glow reflected from hot new stars contained within them.
- C39 is of interest since it is the brightest globular cluster contained within M33, although in my image it is indistinguishable from an isolated foreground star.
I showed my beginner’s image of M33 two years ago – click here to see it. This new image shows a lot more detail due to a longer exposure and improved technique.