Messier 101, also known as the Pinwheel Galaxy (NGC 5457) in Ursa Major, was discovered on March 27, 1781, by Pierre Méchain. It is more than 20 million light years distant, contains around 1 trillion stars, and measures approximately 170,000 light years across (probably quite similar to the Milky Way, although our galaxy is hard to measure from the inside).
M101 has its own group of galaxies (called the M101 Group, obviously), and is one of a collection of groups of galaxies (including our own Local Group) that make up the Virgo Supercluster, a vast conglomeration of more than 100 groups of galaxies.
1886 – Spiral galaxy NGC 2981, in the constellation of Leo, was discovered by Samuel Oppenheim (or possibly Johann Palisa – there is a little uncertainty).
1886 – Barred Spiral galaxy NGC 2926 and spiral galaxy NGC 2944 (both in the constellation Leo Minor) were discovered by Johann Palisa. These two are listed separately from the above NGC 2981 because they are definitely Palisa’s.
1906 – Discovery of asteroid 594 Mirielle by Max Wolf at Heidelberg. It was named after a poem by the French poet Frédéric Mistral. In the poem, written in the Occitan language, Mirèio is a farmer’s daughter who runs away from home to escape her father’s poor choice of suitors for her.
1964 – Launch of Kosmos 27 on a planned trip to study the hostile Venusian atmosphere (when it would probably have been known as Zond 3MV-1 No 3). Unfortunately, an upper stage malfunction resulted in a mission duration of approximately one day, and a fiery death in Earth’s atmosphere.
1968 – Death of Yuri Gagarin, hero of the Soviet Union, aged 34.
On March 24 1860 Karl Theodor Robert Luther discovered the C-type asteroid 58 Concordia from the Düsseldorf-Bilk Observatory. As you may remember (I mention it every so often) Luther discovered 24 asteroids in all. This one was named after the Roman goddess of marital harmony and understanding. The name was chosen by Karl Christian Bruhns, the recently appointed professor of astronomy at the University of Leipzig.
Concordia is a main belt asteroid, 90-odd km wide, orbiting at between 2.5 and 2.8 AU, and taking 4.44 years to orbit the Sun. It is a member of the Nemsis family, a medium-sized asteroid family with about 250 known members, predominantly C-types.
1781 – Messier 105 (NGC 3379). If you think back a couple of days you might remember me mentioning a group of galaxies in Leo containing M95 and M96, both of which were discovered on March 20th 1781. M105 is also in the group, and it was discovered on March 24th 1781, also by Messier’s assistant Pierre Méchain, who was on a roll. Unlike the other two, this one is an elliptical galaxy, and is known to have a supermassive black hole at its centre.
M105 is the brightest elliptical galaxy in this particular group. It is an E1 type, and is approximately 38 million light years away from Earth. The “E” rating for galaxies is based on their elongation, where “E0” is fairly round, while “E7” is extremely stretchy. E1 galaxies are only slightly elongated.
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.