|M83||Spiral Galaxy||13h 37m 01s||-29° 51′ 56″||Hydra||+7.1||13.6×13.2 arcmin|
In our last of three Hydra challenges this April, we’re hunting for M83, which is a beautiful, archetypal, spiral galaxy. The brightest galaxy in the snake constellation is also known as the Southern Pinwheel Galaxy, and is located a long way down the end of its body, adjacent to Centaurus and near Libra.
Its location makes M83 a tricky find for more northern observers. If you live in the mid-latitudes of the US, you’ll see it around 20° over the southern horizon at its best viewing. Head towards the Canadian border, however, and it won’t rise higher than 12°. This makes it harder to get great views, but it is such a rewarding sight that it is definitely worth the effort.
Scientists have discovered that M83 is the same size as our own Milky Way, spanning ~100,000 light-years from edge to edge. As stunning as views like the one below are, it’s amazing to learn that we can’t see 80% of the matter which makes up its mass, it’s hidden in a huge gas disc around the star field we can see. The galaxy is one of the closest to our own, but is still a staggering 14 million light-years away.
It has a bright nucleus and thick central bar. Arms fling out from the bar – two brighter ones and a number of fainter filaments. These all house rich star-forming regions, possibly caused (it is speculated) by the tidal interaction with the nearby dwarf galaxy NGC 5253.
While it won’t look like this image captured by the Hubble Space Telescope, you will get to appreciate its beauty with a good telescope in a dark sky.
This first sky chart for M83 (all on this page are from SkySafari 6) shows just how low in the sky we need to look for the Southern Pinwheel. In the middle of April, we get the best views as it transits the southern horizon around 1am. At that time, it will be 20° above the horizon, a long way from the overhead point (zenith).
Despite its low position in the sky, M83 is fairly easy to track down in your telescope using two stars, one in Hydra and the other in Centaurus.
Imagine a line (orange, in the image below) joining the stars Cauda Hydrae in Hydra (Gamma Hydrae) and Menkent in Centaurus (Theta Centauri). M83 is found halfway along this line.
Zooming in one last time, see stars to magnitude 7.0 and the blue ring which represents a 6° field of view, which is roughly what you’ll see in a magnifying finderscope. The red circles show a set of Telrad finderscope rings.
You can see that when the group of three bright stars h Centauri (mag. 4.7), 3 Centauri (mag. 4.6), and i Centauri (mag. 4.2) are in the southeast quadrant of your field of view, M83 is in the northwest quadrant.
The following views will help you find M83 in different telescope types by presenting the images as your telescope will show them. The first image is with a black sky and white stars, the second picture is the same image but presented in inverse monochrome. Black stars on a white background is often easier to use at the telescope. Each image can be clicked on for a full-screen version.
Upright View – This is what your eyes see unaided and through a reflex or red-dot finderscope (Telrad circles shown)
Upside-down view – This is what reflectors and magnifying finders show, and refractors / Cassegrains without a star diagonal (6° field of view circle shown)
Mirrored View – Refractors and Cassegrain models with a star diagonal show this view
When you pick it up in the telescope, you’ll see a familiar ghostly view, like a blemish that you can’t quite bring to focus.
This is a bright enough object to withstand higher magnification and a larger telescope with good conditions will allow you to see some good detail. You should see that it appears elongated along its central bar. You won’t discern the bar itself, but you should note that the galaxy appears brighter along the southeast-northwest direction.
Higher magnification will expose a brighter central core and a fainter outer region. And, the treat of an object like M83, is the more you look at it and study it, the more detail you will see.
Even if you can’t pick out the spiral arms as individual structures, you should see lighter and darker areas within the Southern Pinwheel’s boundary. You’ll enjoy trying to pick this galaxy apart with many hours at the eyepiece.
Each of the star maps above is reproduced as a pdf below. Each star map has a number in [square brackets] beneath it which corresponds to the file number below. If you want image [M83-1], for example, click the ‘download’ button next to it below and you’ll be able to open it as a printable pdf.