M105 - NGC 3379

Messier 105 (NGC 3379) is an elliptical galaxy located approximately 32 million light-years from Earth in the constellation Leo. It was discovered by Pierre Mechain in 1781 but was not included in Messier's original catalog; it was added later by Helen Sawyer Hogg in 1947 based on Mechain's notes. M105 is classified as an E1 elliptical galaxy and is the brightest elliptical galaxy in the Leo I Group (M96 Group), which also includes the spiral galaxies M95 and M96. The galaxy has a visual magnitude of about 9.3 and a physical diameter of approximately 54,000 light-years. M105 is one of the most extensively studied elliptical galaxies in astronomy, largely because of its proximity and the quality of data available. Hubble Space Telescope observations have revealed a supermassive black hole at its center with a mass of approximately 200 million solar masses, detected through the rapid orbital motion of gas and stars near the nucleus. M105 was also one of the galaxies used to demonstrate that nearly all galaxies with central bulges harbor supermassive black holes, a finding that has become a cornerstone of modern galaxy formation theory. Despite being classified as a featureless elliptical, deep imaging has revealed faint dust patches and a small disk-like structure near the nucleus, suggesting some complexity beneath the smooth exterior. The galaxy is surrounded by a population of approximately 5,700 planetary nebulae that have been used to study its three-dimensional structure and mass distribution. In amateur telescopes, M105 appears as a small, bright, round glow with a concentrated center. It forms a close visual pair with the nearby galaxy NGC 3384, and the fainter NGC 3389 lies nearby, creating an attractive trio in moderate-aperture telescopes.

M105 spans approximately 54,000 light-years in diameter, contains a 200 million solar mass black hole, and lies about 32 million light-years from Earth.