Messier 105 is the largest elliptical galaxy in the Messier catalog and a prominent member of the Leo I Group. It appears relatively featureless and inactive, typical of elliptical galaxies, with a smooth structure composed mainly of older stars. Despite its seemingly dormant nature, Hubble observations have revealed young stars and star clusters, indicating ongoing star formation. At its core lies a supermassive black hole, confirmed by measurements of stellar velocities around the galactic center.
Names and Catalog numbers
- Messier: M105
- NGC: NGC 3379
- UGC: UGC 5902
- PGC: PGC 32256
Position and the cosmic neighborhood
Messier 105 is situated in the eastern part of the constellation Leo, near the border with Virgo. It belongs to the Leo I Group, which includes other notable galaxies such as M95 and M96. In the night sky, M105 can be found approximately two degrees south of the line connecting the stars Chertan (θ Leonis) and Regulus (α Leonis). Nearby, observers can spot two fainter galaxies, NGC 3384 and NGC 3389, which often appear in the same field of view when imaging M105.
Nice to Know
- M105 was discovered by Pierre Méchain in 1781 but was not included in the original Messier catalog; it was added in 1947 based on Méchain’s letter describing the galaxy.
- Despite being considered an “inactive” galaxy, M105 shows evidence of recent star formation, challenging previous assumptions about elliptical galaxies.
- The galaxy is surrounded by a ring of neutral hydrogen with a total mass of 1.8 billion solar masses.
- M105’s central supermassive black hole has an estimated mass of 200 million solar masses.
Brightness, distance and size
Messier 105 has an apparent visual magnitude of approximately 9.3, making it visible through amateur telescopes under dark sky conditions. Located about 32 million light-years from Earth, the galaxy spans roughly 55,000 light-years in diameter. In terms of angular size, M105 appears about 5 by 5 arcminutes across in the night sky, presenting a challenge for astrophotographers to capture its full extent and subtle details against the background of space.