Wikipedia:
Messier 91 (also known as NGC 4548 or M91) is a barred spiral galaxy that is found in the south of Coma Berenices. It is in the local supercluster and is part of the Virgo Cluster of galaxies. It is about 63 million light-years away from our galaxy. It was the last of a group of eight "nebulae" – as galaxies until the next century were not suspected to be visible, the term galaxy being used as a synonym for universe – discovered by Charles Messier in 1781.
Among those few Messier objects in the catalogue as the result of bookkeeping mistakes by Messier long-missing; it was not until 1969 that amateur astronomer William C. Williams realized that M91 was NGC 4548, which was catalogued by William Herschel in 1784. Some sources contend the nearby spiral galaxy NGC 4571 was considered as a candidate for this object by Herschel.
Inclusion of Messier 91 in the Virgo cluster was confirmed in 1997 from observing Cepheid variables which place it at 52 ±6 million light years away.
Its bar is very conspicuous – it is seen with position angle of 65 to 245 degrees when being measured from the North direction to the East.
There is a countering peculiar (local) velocity toward us through the Virgo cluster of about 700 km/s within the cluster's recession velocity of about 1100 km/s, which produces its observed recessional velocity of only about 400 km/s. Another source gives the latter figure as 803 km/s.
Messier 91 is also classified as an anemic galaxy, that is: a spiral galaxy with little star formation and gas compared with other galaxies of its type.
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