Messier 105, NGC 3379

Messier 105 (NGC 3379) is the brightest elliptical galaxy in the Leo I or M 96 group of galaxies.

M 105 was discovered by Pierre Mechain in 1781, only few days after he discovered the nearby galaxies M 95 and M 96. But for unknown reasons, M 105 was not included in Charles Messier's original list, until 1947, when Helen Hogg found a letter by Mechain describing Messier 105. William Herschel had also observed M 105 in 1784, and assigned it the number H I.17.

In telescopes, M 105 appears as a fuzzy ball, only 2' across, that gets brighter near the center. It is of type E1, and often studied as a typical representative of elliptical galaxies. With a visual magnitude of 9.3, Messier 105 is the brightest of an 8'-wide triangle of galaxies that includes NGC 3384 and NGC 3389. This trio is part of the M 96 Galaxy Group, and its distance is about 32 million light-years. While NGC 3384 is probably a member of the same Leo I group as M 105, NGC 3389 is probably a background object, as it is receding at 1138 km/sec, much faster than M 105 (752 km/sec), or the other members of the Leo I group (450 - 760 km/sec).

M 105 is a giant elliptical galaxy with an absolute magnitude of -20.6, corresponding to a luminosity of 15 billion suns. Its true diameter is in excess of 35,000 light years. Investigations with the Hubble Space Telescope have revealed that M 105 contains a supermassive central black hole, of about 50 million solar masses.