Whirlpool Galaxy (M51)

The Whirlpool Galaxy is an interacting grand-design spiral galaxy in the constellation Canes Venatici, estimated to be 23 million light-years away and about 400 million years old. Famous astronomer Charles Messier discovered it in 1773 as Messier 51 (M51), and it eventually earned the nickname “The Whirlpool” from its resemblance to a vortex in the water. 

NGC 5195

NGC 5195, also known as Messier 51b (M51b), is a dwarf galaxy that interacts with the Whirlpool Galaxy. It was discovered and cataloged by Pierre Méchain, a French astronomer who worked with Charles Messier, on March 20, 1781. Now I know some of you are asking, "Andrew, what is happening between these two galaxies?" I've been intrigued by that same question, so I've spent some time studying whether these two galaxies are colliding, merging, or just gliding through the black abyss together. With the help of observing NASA's Chandra Space Telescope discoveries, I was able to find some fascinating details on this phenomenon. 

In the photo above, taken by NASA's Chandra X-ray Observatory, Astronomer's discovered that one of the nearest supermassive black holes in the Messier 51 galaxy and NGC 5195 was currently undergoing powerful outbursts. The image to the right of the two galaxies reveals details of the Chandra data (blue) of this region. Researchers found a pair of arcs in these X-ray emissions close to the galaxy's center, which they interpret as two outbursts from the galaxy's supermassive black hole.

NASA suspects that these outbursts of the supermassive black hole in NGC 5195 may have been triggered by the interaction with the large spiral galaxy in M51, causing gas to be disrupted and then funneled down toward the black hole. This makes me believe these two galaxies will collide, whether the dust of each floats endlessly off into space or merges into a super-galactic galaxy.

Location & Best Time to See it

The Whirlpool Galaxy is one of the brightest galaxies in our sky, as it is located between the constellations Canes Venatici and Ursa Major. An easy way to find the Messier 51 is by looking for the star at the tail of the big dipper, Alkaid, and moving upwards. The photo below from Stellarium is a good representation of where to look to find the Whirlpool Galaxy in the night sky.

From mid-northern latitudes, it reaches an apparent altitude high enough in the southern sky for visual observation or photograph. For latitudes greater than 42N, it's circumpolar and therefore, never sets. However, it is best to view it at its peak in the sky close to the zenith to minimize the effects of turbulence in the air and localized light pollution. So, the best time to observe the Whirlpool Galaxy during the year is from March to May.

Photographing the Whirlpool Galaxy

Messier 51 is one of the brightest targets in the night sky, easily seen through binoculars or a simple telescope. With a large aperture, you would even be able to see its neighbor, NGC 5195. Because of the Whirlpool Galaxy's large apparent magnitude, you can faintly capture the core and arms of this galaxy with just a short 1-minute exposure shot. This is really helpful when trying to locate Messier 51 through your camera and telescope. Once you have the Whirlpool Galaxy in frame and tracking, we will need to take the four main calibration frames (light, dark, flat, and bias) for deep sky objects, and stack these shots together through DeepSkyStacker. A good tutorial on how to use the software is here.

Here is how to take the four main calibration frames:

Light Frames - These are your signal frames; the instructions above are how to take these.

Dark Frames - These frames' purpose is to increase your photo's signal-noise ratio. Keep the same settings you had for your light frames and cover your lens/telescope with the lid. 

Bias Frames - The purpose of these frames is to reduce the noise in your photo. Keep the same settings on your camera for your light frames, change the exposure time to the fastest it can possibly be, and cover your lens/telescope with the lid. 

Flat Frames - The purpose of these frames are to eliminate vignetting/light falloff and other artifacts in your image due to dust, dirt, or smudges on the sensor or telescope in your photo. These are tricky. In simple terms, cover your lens/telescope with a white shirt and point it at a constant light source, like the morning sky. Then experiment with the exposure times until the histogram looks like the one below. This is shown below for monochrome and color cameras.

My photo of Messier 51 below was captured using an unmodified Canon Rebel EOS T3i (600D) DSLR camera and a refractor telescope (100mm Aperture, 900mm focal length). This was the first deep sky photo I was able to capture, which I am very proud of. However, there is still much room for improvement.

Whirlpool Galaxy Details:

• Messier: 51

• NGC: 5194

• Object Type: Grand-Design Spiral Galaxy

• Constellation: Canes Venatici

• Distance: 23 million light-years

• Apparent Magnitude: +8.4

• Apparent Size: 11 x 7 Arc Minutes

Resources:

Messier 51 - The Whirlpool Galaxy (NASA) 

StarCharts - Whirlpool Galaxy

Galaxy NGC 5195 (NASA)

Gallery of Whirlpool Galaxy