Discovered by Pierre Méchain in 1781.

M105 is the brightest elliptical galaxy in the Leo I or M96 group of galaxies, and as such approximately 38 million light years distant. It is of type E1, and often studied as a typical representative of elliptical galaxies; e.g., J.D. Wray's Color Atlas of Galaxies states: "This elliptical galaxy is a photometric standard for surface brightness distribution," and mentions the uniformity of color over the entire range of luminosity.

Investigations with the Hubble Space Telescope of the central region of M105 have revealed that this galaxy contains a massive central object of about 50 million solar masses.

M105 is the bright elliptical at left in our image. Below and right of center is NGC 3384, while the galaxy in the upper right is NGC 3389. This is also the order of increasing difficulty. While NGC 3384 is probably a member of the Leo I group as M105, NGC 3389 is probably a background object, as it is receding from us at 1138 km/sec, much more than M105 with its 752 km/sec, or the other members of the Leo I group at about 450..760 km/sec.

M105 was discovered by Pierre Méchain on March 24, 1781, even 3 days earlier than M101, but due to unknown reasons, although probably intended, not included in Charles Messier's published list. Méchain described this object in his letter of May 6, 1783. This additional object was included in the Messier Catalog by Helen B. Sawyer Hogg in 1947, together with M106 and M107. William Herschel had observed it on March 11, 1784, and assigned it his number H I.17.