Spotting the Whirlpool Galaxy

Finding galaxies in the night sky is a very enjoyable and wonderous experience. Up until the early 1900’s, galaxies were thought to be nebulae, some with a spiral shape. After studies by astronomer Edwin Hubble, it was discovered that these spiral nebulae weren’t nebulae, but distant galaxies similar to our own Milky Way.

M51 Whirlpool Galaxy 

One of the most unique galaxies that you can view from your own backyard is the M51 Whirlpool Galaxy. It is fairly easy to find, and this time of year is the best time of year to spot it, as it lies almost overhead right as it gets dark. Dark, moonless skies away from the light pollution is required, as M51 is somewhat dim. Eagle-eyed skywatchers may be able to catch a glimpse through binoculars, but most people will need a telescope. Most telescopes will pick it up, however the larger your telescope is, the more details you will be able to see.

Location of M51 near the Big Dipper, highlighted in the blue box

To find M51, you will first need to find the constellation Ursa Major, also known as the Big Dipper. It can be found in the northern part of the sky. In mid-June, it can be found nearly overhead after sunset for those living in mid-northern latitudes. Once you have spotted the Big Dipper, find the star that marks the end of the handle. This star is named Alkaid. If the bottom of the Big Dipper were parallel to the horizon, you would aim your telescope directly below Alkaid. Slowly scan until you see a faint, cloud-like object somewhat shaped like a question mark. That is M51!

M51 wide field view in a telescope

I have found it easiest to use an eyepiece with a wide-field view to initially find M51. Once I have found it, I’ll increase magnification from there. How much magnification you should use depends on the size of your telescope and the darkness of your sky. The darker the sky and the larger your telescope is, the more magnification you can use.

After finding M51, the first thing you will notice are the two bright cores of the two galaxies. You will also see nebulosity surrounding the two cores. With larger telescopes, you may be able to make out the spiral arms, and the connecting bridge of stars and gas between the two galaxies as well if seeing conditions are optimum.

As you take a nice, long stare at M51, remember that these colliding galaxies are nearly 25 million light years away. M51 was discovered by Charles Messier in 1773, and the smaller companion galaxy (also known as NGC-5195) was discovered in 1781 by Pierre Méchain. It wasn’t known until later that M51 was interacting with NGC-5195 with the advent of radio astronomy.

Sketch of M51 by Lord Rosse in 1845

In 1845, William Parsons (the 3rd Earl of Rosse) viewed M51 through a 72 inch telescope in Ireland and discovered the spiral structures, marking the first time a galaxy was shown to have a spiral shape. It is believed that M51’s spiral shape came from NGC-5195 passing through M51 at least once before, around 500-600 million years ago, then possibly again around 50-100 million years ago. The interactions between M51 and NGC-5195 has triggered a burst of new star formation in the center of M51, and within the spiral arms. M51 is approximately 43,000 light years across, and is approximately 35% the size of the Milky Way. 

M51 also appears to be part of its own group of galaxies, consisting of M51, NGC-5195, the nearby spiral M63 Sunflower Galaxy, the edge-on facing NGC-5023, NGC-5229, and UGC-8313 galaxies, and the irregular UGC-8331 galaxy. M51 is the brightest galaxy of the group. The M51 group can be found mainly in the constellation Canes Venacti, just below the Big Dipper’s handle. It is unsure whether or not the M51 group is its own group, or if it’s part of the nearby M101 group of galaxies.

Viewing galaxies is very fun and amazing. These very distant objects give us insight on our own Milky Way galaxy, and also might invoke some wonder when you take into consideration the distances involved and how vast our universe is! M51 is very unique, as it allows you to glimpse two galaxies interacting with each other, and is fairly easy to find in a dark sky. So, remember to take a look at M51 and be prepared to be amazed!

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