Messier 93, NGC2447, was discovered on this day in 1781. This binocular object is an open cluster about 3,600 light years away, spanning approximately 10 light years, in the constellation Puppis. It was the last open cluster to be discovered by Charles Messier himself. M93 contains a good collection of blue giant stars, as well as quite a few red giants, possibly in clusters of their own. It’s hard to say how many stars a cluster contains, mainly because they get in each other’s way when you try to count them. This one has at least 80 identifiable members, but may well turn out to be several hundred strong.
Messier 95 is a great example of a barred spiral with a “circumnuclear ring”. It, too, was discovered on March 21st 1781, and is a member of the Leo I group of galaxies.
The final member of today’s triple bill is Messier 96. It was identified by Messier’s assistant Pierre Méchain, and is the largest member of the Leo I group. Unlike M95 it has an asymmetrical structure and an off-centre nucleus, the result of gravitational interractions with other members of the group.
The Leo I group also contains M101, and they are located about 35 to 40 million light years away. All three should show up as grey fuzzy patches in small telescopes, given suitable viewing conditions.