Caption: Image of the Sombrero Galaxy (M104, NGC 4594) in constellation Virgo---but it's NOT clear if is a member of the Virgo Cluster.

Features:

1. The image is a mosaic of six images taken by the Hubble Space Telescope's (HST) Advanced Camera for Surveys (ACS), 2003 May--June (exposition time: 10.2 hours).

2. The Sombrero Galaxy characteristics:
   1. Location: in Virgo.
   2. Association: it "lies within a complex, filament-like cloud of galaxies that extends to the south of the Virgo Cluster," but it is NOT clear if it should be considered a member of the Virgo Cluster (Wikipedia: Sombrero Galaxy: Nearby galaxies and galaxy group information.
   3. Hubble type: Sa spiral.
   4. Distance measures: r = 9.0 ± 0.49 Mpc, radial velocity = 1024 ± 5 km/s, redshift = 0.003416 ± 0.000017.
   5. Inclination of axis from line of sight: ≅ 84° (i.e., it seen nearly edge-on).???
   6. Galactic disk: diameter: 17 kpc; angular diameter: 6 arcminutes ≅ 1/5 of the Moon's angular diameter.

3. The large galactic bulge is the giveaway for the Sombrero Galaxy being an Sa spiral even though the spiral arms are NOT easily discerned because the Sombrero Galaxy is seen nearly edge-on.
   If you ignore the lower part of the bulge, the Sombrero Galaxy looks a bit like a sombrero which is convenient given its name.

4. Note the strong dust lane in the galactic disk: this is a hallmark of spiral galaxies.

5. There is a swarm of about 1200 to 2000 globular clusters in the galactic halo (Wikipedia: Sombrero Galaxy: Globular clusters). This is of order 10 times more than the Milky Way has. These globular clusters, like the Milky Way's are calculated to be about 10--13 Gyr old.????

6. It is hard to tell which of the star-like objects in the halo are dim foreground stars in the Milky Way and which are globular clusters, but we know some of them are globular clusters.

   Objects with points are obviously bright foreground stars.

   The points are part of the diffraction pattern that heavy overexposure brings out.

7. In the central region of the Sombrero Galaxy, there is a strong X-ray source and the stars there have very high orbital velocities. These results have led to the conclusion that there is a central supermassive black hole of mass of about 10**9 M_☉ which is near the upper range for the mass of supermassive black holes (Wikipedia: Sombero Galaxy: Central supermassive black hole).