Located on the borders of the constellations Virgo and Corvus approximately 31 million light years distant^[1,4] is the Sombrero Galaxy. (M104, NGC 4594)  In visible light, the galaxy displays a large bright central core encircled by a prominent spiral disk[2].  This structure resembles a wide-brimmed hat^[5] and is the source of its common name.

The galaxy has a very large surrounding halo making its classification unclear^[1].  Infrared studies by NASA's Spitzer Space Telescope has determined M104 is actually two galaxies in one comprised of a large elliptical galaxy with a disc embedded within^[5].  This embedded disc is the hallmark of an nearly edge on spiral galaxy^[2].  Jisu Kang et al^[3] has determined M104's halo is comprised of two distinct regions.  The inner portion is metal rich and probably was formed by a major galaxy merger and the metal poor outer portion is the result of numerous minor mergers^[3,4].  Studies using the Hubble Telescope have also detected metal rich stars in the halo^[6].  They proposed what is known as a "wet" merger.  In the case of M104, the early large elliptical galaxy was infused with large amounts of gas and dust from another massive galaxy.  This merger then fueled the formation of the disc we observe today^[6].  Evidence supporting this scenario is still lacking, however; such a merger could have occurred billions of years ago and cannot be ruled out^[6].

A large number of globular clusters associated with M104 have been observed usuing the Hubble Telescope^[2].  Some of these clusters are visible in the image above as faint star-like objects scattered within M104's surrounding halo.  This observation was confirmed by comparison to Hubble's detailed image^[2].