M33 - Triangulum Galaxy

Messier 33 or M33 (also designated NGC 598) is a spiral galaxy in the constellation Triangulum. It has an apparent visual magnitude of 5.7 and its angular diameter is 73x45 arc-minutes. M33 lies at an estimated distance of 3 million light years. The Equinox 2000 coordinates are RA= 1h 33.9m, Dec= +30° 39´ which makes M33 best seen during the autumn. The Messier Autumn Star Chart shows the position of all Messier objects visible during that season. As one of the more famous objects in the Messier Catalog, it is commonly known as the Triangulum Galaxy.

This spiral galaxy was discovered by Messier in 1764. Under exceptionally good conditions, M33 can be seen with the naked eye making it the most distant object visible without optical aid. M33 is part of the Local Group of galaxies which includes our own Milky Way Galaxy, the Andromeda Galaxy (M31) and others. According to Stoyan et al. (2010), the distance of M33 is 2.74 million light years and its diameter is 60,000 light years. Its estimated mass is 10-40 billion solar masses.

For more information, see the Messier Catalog as well as specific entries for M33 in Wikipedia and SEDS.

Messier's Description of M33

August 25, 1764
`Nebula discovered between the head of the Northern Fish [of Pisces] and the great Triangle, a bit distant from a star of 6th magnitude: The nebula is of a whitish light of almost even density [of brightness], however a little brighter along two-third of its diameter, and contains no star. One sees it with difficulty with an simple refractor of 1 foot. Its position was determined from Alpha Trianguli. Reviewed on September 27, 1780.' (diam. 15')

Technical Details




M33 - Triangulum Galaxy

M33
M33
TAK E180
2011 Jan 25

M33
M33
ASA N12
2011 Nov 23

M33
M33
ASA N12
2013 Dec 24




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