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.