Galaxies M95, M96, M105

Messier 95  (also known as M95 or NGC 3351) is a barred spiral galaxy about 38 million light-years away in the constellation Leo. It was discovered by Pierre Méchain in 1781, and catalogued by Charles Messier four days later. On 16 March 2012, a supernova was discovered in M95.

Messier 96  (also known as M96 or NGC 3368) is an intermediate spiral galaxy about 31 million light-years away in the constellation Leo. It was discovered by French astronomer Pierre Méchain on March 20, 1781. After communicating his finding, French astronomer Charles Messier confirmed the finding four days later and added it to his catalogue of nebulous objects. Finding this object is extremely difficult with binoculars. With a telescope of 25.4 cm (10.0 in) aperture, the galaxy is visible as a 3 × 5 arcminute halo with a brighter core region.

This complex galaxy is inclined by an angle of about 53° to the line of sight from the Earth, which is oriented at a position angle of 172°. It is categorized as a double-barred spiral galaxy with a small inner bulge through the core along with an outer bulge. The nucleus displays a weak level of activity of the LINER2 type. Variations in ultraviolet emission from the core suggest the presence of a supermassive black hole. Estimates for the mass of this object range from 1.5×10⁶ to 4.8×10⁷ times the mass of the Sun.

On May 9, 1998 a supernova event was observed in this galaxy. Designated SN 1998bu, this was a Type Ia supernova explosion. It reached maximum light on May 21 then steadily declined in magnitude thereafter. Observations of the ejecta a year later showed that the explosion created 0.4 times the mass of the Sun worth of iron. The spectrum of the supernova remnant confirmed the presence of radioactive ⁵⁶Co, which decays into ⁵⁶Fe.

Messier 105 (also known as M105 and NGC 3379) is an elliptical galaxy in the constellation Leo. Messier 105 was discovered by Pierre Méchain on 24 March 1781, just a few days after he discovered the nearby galaxies Messier 95 and Messier 96. This galaxy is one of several that were not originally included in the original Messier Catalogue compiled by Charles Messier. Messier 105 was included in the catalog only when Helen S. Hogg found a letter by Méchain describing Messier 105 and when the object described by Méchain was identified as a galaxy previously named NGC 3379.