Messier 105 or M105 (also designated NGC 3379) is a elliptical galaxy in the constellation Leo. It has an apparent visual magnitude of 9.3 and its angular diameter is 2 arc-minutes. M105 lies at an estimated distance of 38 million light years. The Equinox 2000 coordinates are RA= 10h 47.8m, Dec= +12° 35´ which makes M105 best seen during the spring. The Messier Spring Star Chart shows the position of all Messier objects visible during that season.

The image above shows the uncropped view of M105 (top), M96 (left) and M95 (right) through the Takahashi E-180 Astrograph (North is up). A 3x enlargement of this image centered on M105 appears to the right. About 8 arc-minutes east of M105 are elliptical galaxy NGC 3384 and spiral galaxy NGC 3389.

This elliptical galaxy was discovered by P. Méchain in 1781. M105 is the brightest elliptical galaxy in the Leo I group of galaxies, which includes M95, M96 and a number of fainter galaxies. According to Stoyan et al. (2010), the distance of M105 is 37.9 million light years and its diameter is 55,000 light years. Its estimated mass is 100 billion solar masses.

For more information, see the Messier Catalog as well as specific entries for M105 in Wikipedia and SEDS.

Messier's Description of M105

Méchain in his letter to Bernoulli, May 6, 1783)
`Mr. Messier mentions there on page 264 and 265 two nebulous stars, which I have discovered in the Lion [Leo; M95 and M96]. I find nothing to correct for the given positions which I have determined by comparison of their situation with respect to Regulus. There is, however, a third one, somewhat more northerly, which is even more vivid [brighter] than the two preceding ones [M95 and M96]. I discovered this one on March 24, 1781, 4 or 5 days after I had found the other two. On April 10, I compared its situation with Gamma Leonis from which followed its right ascension 159d 3' 45" and its northern declination of 13d 43' 58".'

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