|Rektascenzija||13 : 29.9 (u:m)
|Deklinacija||+47 : 12 (sto:m)
|Razdalja||37000 (*1000 sv.l.)
|Vizual. magnituda||8.4 (mag)
|Zorni kot||11x7 (loc min)
The famous Whirlpool galaxy M51 was one of Messier's original discoveries: He discovered it on October 13, 1773, when observing a comet. Its companion, NGC 5195, was discovered in 1781 by his friend, Mechain, so that it is mentioned in his 1784 catalog: `It is double, each has a bright center, which are separated 4'35". The two "atmospheres" touch each other, the one is even fainter than the other.' NGC 5195 was assigned an own number by William Herschel: H I.186.
M51 is the dominating member of a small group of galaxies. As it is about 37 million light years distant and so conspicuous, it is actually a big and luminous galaxy.
This galaxy was the first one where the spiral structure was discovered (Lord Rosse, 1845, who made a very careful and acurate painting). According to our present understanding, the pronounced spiral structure is a result of M51's current encounter with its neighbor, NGC 5195 (the fainter one in Messier's description).
For the amateur, it is easy and a showpiece if the sky is dark, but is quite sensitive for light pollution which easily makes it fade in the background. Under very cood conditions, even suggestions of its spiral arms can be glanced with telescopes starting from 4-inch. Low magnification is best for viewing this pair.
The Hubble Space Telescope has investigated especially the central region of M51. ESA's ISO (Infrared Space Observatory) satellite has investigated the Whirlpool Galaxy in the infrared light.
In 1994, a supernova (1994I) was discovered in M51, by the Atlanta amateur astronomers Jerry Armstrong and Tim Puckett.
The companion galaxy, NGC 5195, has also produced one supernova, 1945A,
which occurred on April 8, 1945, and reached 14th magnitude.