Observing Project 14C Showcase Spirals and Their Oddball Companions

Two showcase galaxies that pass high overhead in the evening sky for northern observers are M51 and its companion NGC 5195 in Canes Venatici and the spiral M81 and its irregular companion M82 in Ursa Major.

M81 is the easier galaxy to find because it is so much brighter. To find M81, first locate the bluish star Dubhe at the end of the pot of the Big Dipper. To star hop to M81 from here is difficult because there are few descript stars here that stand out and the galaxy is a full ten degrees from Dubhe. Scan about 5 degrees to the north and west of Dubhe to find a group of four fifth-magnitude stars, three of which form a triangle. The brightest of these stars is magnitude +5.7 32 Ursae Majoris. Move past this group in roughly the same direction, perhaps slightly more to the north. As the four fifth-magnitude stars vanish out of the edge of the field, the magnitude +4.5 magnitude star 24 Ursae Majoris appears in your finder. Move your telescope then about 2 degrees back towards the south and east to center on M81. You might have passed M81 on the way between 32 and 24UMa. These stars are obscure so make sure you have the map handy!

M81 has a bright central core that is easy to see in just about any telescope. The challenge is to see any trace of its spiral structures in a medium or small telescope. That dominant core earns it a Shapely class Sb. The arms are areas of active star forming perhaps triggered by interaction with the nearby companion galaxy, M82.

The two galaxies are separated by less than 0.6 degrees and are easily visible in the same telescopic field even without extra wide field setups. M82 is the only irregular galaxy in the Messier catalogue. Called the "Cigar Galaxy" for its stogie-like profile, this galaxy may have once been a spiral or lenticular galaxy before being gravitationally disrupted and deformed by M81. M82 is also relatively bright shining at magnitude +8.2. I can see them both at zenith from my light-polluted yard in Newark, DE on a night with good transparency. Together they make one of the great showcase pairs of galaxies in the northern sky.

A rival pair of galaxies that vies for that title is M51 and its irregular partner NGC 5195. To find this galaxy, start at the other end of the Big Dipper where the magnitude +1.8 star Alkaid marks the end of the handle of the Dipper. From Alkaid, go south and slightly west by 2.2 degrees where you will easily find the magnitude +4.7 star 24 Canes Venatici. There is no other star around bright enough to confuse it with. From 24CVn, go south and slightly east by about 2 degrees to find a nearly equilateral triangle of three magnitude-seven stars. M51 can be found just to the south of this triangle.

The Whirlpool Galaxy can be tough to see despite a relatively bright total magnitude of +8.4. It has an extremely low surface brightness that makes it at times very tough to find. M51's companion, NGC 5195, is an irregular type galaxy that appears to be just emerging from a close encounter with M51. Because of the manner in which Messier described the two structures, NGC 5195 is sometimes called M51B. The galaxy passed M51 traveling away from us along our line of sight and is now slightly behind M51. NGC 5195 appears at one point to have been a disk-shaped galaxy, maybe a lenticular or a spiral, we don't know for sure but has now become an irregular galaxy because of the gravitational disruption caused by M51. Images of the pair make it appear that NGC 5195 is touching one of the outer spiral arms. Light pollution will pretty quickly make this galaxy impossible to see, so seek M51 on nights of good transparency and under a dark sky. As with other galaxies, an LPR filter will help, but only as far as suppression of sky glow is concerned.

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