There’s much to observe in December night sky

Most amateur astronomers look forward to spring because it is “Galaxy Season,” and that is when many (more than 100) galaxies can be seen in medium to large amateur telescopes. However, even in December, there are a few galaxies that can be seen — they are just more difficult to find than in spring.

For example, one nearby galaxy, M33, can be seen in December. M33 is part of the so-called Local Group. The Local Group is a group of about 15 galaxies, of which our own Milky Way galaxy is a member. The three brightest members of these galaxies in the Local Group are M31, in the constellation Andromeda, our Milky Way, and M33. It is M33 that I will discuss here.

Many of the most skilled amateurs have never seen M33, though they may have repeatedly sought it. It is difficult to find because, while it is only 2.75 million light-years away [close as intergalactic distances go], it has low luminosity. It is a big galaxy, but its surface brightness is low, making it dim unless under a very dark, clear sky.

M33 is a spiral galaxy, as is M31 and the Milky Way. It is positioned in the sky, face-on to us, so photographic images of it reveal that it somewhat resembles a pinwheel. As all spiral galaxies show, they are full of gas and dust that have not yet formed into stars. M33 is no exception. It does have 70 to 80 billion stars, however, and that lets us see it, even if it is dim.

I have tried many times to find this galaxy, and I have tried to get an image of it since my particular interest in amateur astronomy is astrophotography. About two weeks ago, with the help of a friend who is more sharpeyed than I, I did find it, and I made an image of it with a 5-inch refractor telescope. I have included it in this column. As I render it, it has a bluish cast because most of the stars an amateur might image are very big, bright bluish stars, such as those found in the arms of all spiral galaxies.

It is near Christmas, and I imagine some of you might get a telescope for Christmas. Good for you! Train your new ‘scope’ on the Moon and be thrilled! Now, also, I recommend you put that telescope on Jupiter, which will appear almost directly overhead this month. In fact, overhead, it will be the brightest single dot of light you can see with the naked eye, excluding the Moon.

See if you can spot four of Jupiter’s moons and, from night to night, watch the array of moons change. Depending on your telescope, you might even see some of the moons pass in front of Jupiter itself. If you make these observations, you will be doing what Galileo did in about 1615 — seeing the moons of Jupiter and seeing them move around the great planet!

The new year is coming soon! I want to thank my readers for sticking with me this past year. It has been a great year for sky-watchers like you and me. Next year will be too!

Merry Christmas to all of you!