M104 more commonly known as the Sombrero Galaxy is a spectacular, almost edge-on, spiral galaxy located in Virgo. At magnitude +8.4, the Sombrero appears in binoculars as a small patch of nebulosity. Its most striking feature - visible in medium/large sized amateur scopes - is a ring of thick dust that encapsulates the bulge of the galaxy, giving the appearance of a Sombrero hat. Many astronomers regard M104 as the finest of all galaxies in Virgo.

Pierre Méchain discovered M104 on May 11, 1781. A couple of years later he described the galaxy in a letter to Johann Bernoulli and subsequently it was published in the Berliner Astronomisches Jahrbuch (Berlin Astronomy Year Book). Charles Messier made hand-written notes about this and five other objects but none were included in the final published catalogue version. The Sombrero Galaxy was finally added to the "official" catalogue in 1921 with the other five "missing" items (M105 to M109) added a few years later.

M104 was one of the first galaxies to have its spectra and velocity measured by Vesto Slipher in 1912. He noted that the object was redshifted and therefore receding from us, the current accepted rate being 900 km/s. Slipher's redshift calculation of M104 along with similar observations from other galaxies pointed towards an expanding Universe, hence providing a key piece of evidence for the Big Bang Theory.

The Sombrero Galaxy is located very close to the constellation boundary between Virgo and Corvus. It's positioned 11.5 degrees directly west of Spica (α Vir - mag. +1.0) and 6 degrees northeast of delta Crv (δ Crv - mag. +2.9). The stars chi Vir (χ Vir - mag. +4.7), psi Vir (ψ Vir - mag. +4.8) and 21 Vir (mag. +5.5) form a faint naked-eye triangle just north of M104.

It's best seen during the months of March, April and May.

M104 The Sombrero Galaxy by the Hubble Space Telescope (NASA, The Hubble Heritage Team (AURA/STScI))

Finder Chart for M104

Finder Chart for M104 - pdf format

Finder Chart for M61 (also shown M49 and M104)

Finder Chart for M61 (also shown M49 and M104) - pdf format

Through 7x50 or 10x50 binoculars, M104 is visible under dark skies as a small, round patch of nebulosity. The galaxy is easy to observe with almost any telescope. A 100mm (4-inch) scope under good seeing conditions will hint at a dark band within the structure. When seen through larger 200mm (8-inch) scopes, M104 appears as a flattened saucer with a large bulge bisected by a dark lane. Even larger amateur instruments of the order of 250mm (12-inch) aperture reveal a bright nucleus, extensive halo and the dark dusk lane extending outwards on both sides. On good nights, the Sombrero Galaxy is a spectacular sight.

M104 covers 8.6 x 4.2 arc minutes of apparent sky. It's located 30 million light-years distant, which corresponds to an actual diameter of 75,000 light-years. The galaxy is estimated to contain about 100 billion stars. It contains a reasonable large number of globular clusters, as many as 2,000. M104 is also the dominant member of a small group of galaxies known as the M104 group or NGC 4594 group.

M104 Data Table

Messier104
NGC4594
NameSombrero Galaxy
Object TypeSpiral galaxy
ClassificationSa (s) a
ConstellationVirgo
Distance (kly)30000
Apparent Mag.8.4
RA (J2000)12h 39m 59s
DEC (J2000)-11d 37m 23s
Apparent Size (arc mins)8.6 x 4.2
Radius (light-years)37,500
Number of Stars100 Billion

Sky Highlights - April 2017

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