M51, The Whirlpool Galaxy
This is the evocative and justifiably famous Whirlpool galaxy (also known as M51a or NGC 5194) and its companion galaxy M51b (also known as NGC 5195). First sketched as a spiral by Irish astronomer Lord Rosse using the 72" Leviathan of Parsonstown in 1845. The Leviathan was the largest telescope of its day, and he used it to resolve what others had just seen as a mysterious smudge of shimmering light. French astronomer Charles Messier, 72 years earlier, had named the glowing “blob” M51 while hunting for comets.
Messier’s blob took on a more intricate form with Lord Rosse’s powerful telescope. To the Irish astronomer’s surprise, the glowing blob had a striking pinwheel shape that no one had ever seen before. Lord Rosse simply called M51 a “spiral nebula,” not realizing that the glowing spiral-shaped object was a faraway galaxy. The interacting pair do battle about 23-million light-years from Earth, in the constellation Canes Venatici, or 10 times further than Andromeda M31.
The Whirlpool galaxy is interacting gravitationally with M51b, and is called a ‘grand-design’ because it has well-defined spiral arms (like M101 and our Milky Way). Gravitational forces exerted on the Whirlpool galaxy by its companion are helping to drive M51a’s star formation. You can see the fruits of this interaction by looking at the bright blue star clusters (the largest concentrations being closest to M51b). Within these blue pockets are the youngest stars in the Whirlpool Galaxy. In contrast, the oldest stars can be found near the Whirlpool’s central bulge.
There are a few foreground stars seen here, located within our own Milky Way. In contrast, in the background you can see several galaxies which are much further away than the Whirlpool. To catch them all, use the O setting in the Size menu after you've clicked on the image. This was the 3rd picture taken in a single night after about 3 months of nothing due to horror English cloud...the others taken that night are Abell 1656 and the Whale/Hockey Stick combination.
Orion Optics UK AG16 Astrograph: SBIG 11000 CM: Titan Mount
25 x 5 minutes minutes (2hr 5 minutes total) single shot colour, processed with CCDStack, Photoshop, Pixinsight.
Data capture: between 2.15 and 4.30 am, 7th April 2013