M 104

Spiral Galaxy M104 (NGC 4594), type Sa,

Sombrero Galaxy

to the official Messier list.

This brilliant galaxy was named the Sombrero Galaxy because of its

appearance. According to de Vaucouleurs, we view it from just 6 degrees

south of its equatorial plane, which is outlined by a rather thick dark

rim of obscuring dust. This dust lane was probably the first discovered,

by William Herschel in his great reflector.

This galaxy is of type Sa-Sb, with both a big bright core, and as one can

see in shorter exposures, also well-defined spiral arms. It also has an

unusually pronounced bulge with an extended and richly populated globular

cluster system – several hundred can be counted in long exposures from big

telescopes.

This galaxy was the first one with a large redshift found, by V.M. Slipher

at Lowell Observatory in 1912. Its redshift corresponds to a recession

velocity of about 1,000 km/sec (it is caused by the Hubble effect, i.e.

the cosmic expansion). This was too fast for the Sombrero to be an object

in our Milky Way galaxy. Slipher also detected the galaxy’s (then the

nebula’s) rotation.