Virgo is a constellation famed for its huge population of distant celestial smudges, one of which is our first object, Messier 104. M104 actually sits close to the border between Virgo and the more southerly constellation Corvus, approximately 11° from the bright star Spica (Alpha Virginis). M104 is more commonly known as the Sombrero Galaxy and it’s not difficult to see how it acquired this name when you look at it through a large telescope or see images of it taken by astrophotographers. Its scientific story is every bit as striking as its visual appearance too.
Perhaps its most obvious feature is the dark swathe across the bright mass of stars that make up its glowing oval shape. The swathe is a silhouetted portion of the galaxy’s disc of dust and gas, which is viewed edge on from our line of sight. Hubble Space Telescope images have shown this disc in remarkable detail, revealing intricate structures in the dust lanes there. Infrared observations made with the Spitzer Space Telescope meanwhile have revealed that, unusually, M104’s disc sits within another, larger elliptical galaxy, only part of which we see in visible light and which only becomes more fully apparent at longer infrared wavelengths.
The dark dust lane encircling M104 contributes to its Sombrero-like appearance; inset: seen in infrared, M104’s secret is revealed – it’s actually two galaxies in one