Sombrero Galaxy
The Sombrero Galaxy (also known as M 104 or NGC 4594 ) is an unbarred spiral galaxy in the constellation Virgo. It has a bright nucleus, an unusually large central b
ulge, and a prominent dust lane in its inclined disk. The dark dust lane and the bulge give this galaxy the appearance of a sombrero. The galaxy has an apparent magnitude of +9.0, making it easily visible with amateur telescopes.
ulge, and a prominent dust lane in its inclined disk. The dark dust lane and the bulge give this galaxy the appearance of a sombrero. The galaxy has an apparent magnitude of +9.0, making it easily visible with amateur telescopes.History
Discovery
The Sombrero Galaxy was discovered in March of 1767 
by Pierre Méchain, who described the object in a May 1767 letter to J. Bernoulli that was later published in the Berliner Astronomisches Jahrbuch.
by Pierre Méchain, who described the object in a May 1767 letter to J. Bernoulli that was later published in the Berliner Astronomisches Jahrbuch.William Herschel independently discovered the object in 1784 and additionally noted the presence of a "dark stratum" in the galaxy's disc, what is now called a dust lane. Later astronomers were able to connect Méchain's and Herschel's observations.
Designation as a Messier object
In 1921, Camille Flammarion found Messier's personal list of the Messier objects including the hand-written notes about the Sombrero Galaxy. This was identified with object 4594 in the New General Catalogue, and Flammarion declared that it should be included in the Messier Catalogue. Since this time, the Sombrero Galaxy has been known as M104.
Historical redshift measurements
In the 1910s, Vesto Slipher discovered that the spectra of several galaxies, including the Sombrero Galaxy, are redshifted. The average velocity calculated from these redshifts was 400 km/s. The redshift for the Sombrero Galaxy itself was calculated to be 1100 km/s.
Dust ring
As noted above, this galaxy's most striking feature is the dust lane that crosses in front of the bulge of the galaxy. This dust lane is actually a symmetric ring that encloses the bulge of the galaxy. Most of the cold atomic hydrogen gas and the dust lies within this ring.
Additional observations are needed to confirm that the Sombrero galaxy's molecular gas is constrained to the ring. Based on infrared spectroscopy, the dust ring is the primary site of star formation within this galaxy.
No comments:
Post a Comment