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The Heart of the Lion
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Name: M105, Messier 105, NGC 3379
Description: Elliptical Galaxy
Position (J2000): RA 10h 47m 49.63s Dec 12° 34' 55.76"
Constellation: Leo
Distance: 32 million light years
Visual magnitude: 10.2
Angular size: 5.4 × 4.8 arcmin
Field of view: 6.31 x 6.39 arcminutes
Orientation: North is 127.8° right of vertical
Image Credit: ESA/Hubble & NASA, C. Sarazin et al
Release date: January 7, 2019

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It might appear featureless and unexciting at first glance, but NASA/ESA Hubble Space Telescope observations of this elliptical galaxy - known as Messier 105 - show that the stars near the galaxy's center are moving very rapidly. Astronomers have concluded that these stars are zooming around a supermassive black hole with an estimated mass of 200 million Suns! This black hole releases huge amounts of energy as it consumes matter falling into it and causing the center to shine far brighter than its surroundings. This system is known as an active galactic nucleus.

Hubble also surprised astronomers by revealing a few young stars and clusters in Messer 105, which was thought to be a "dead" galaxy incapable of star formation. Messier 105 is now thought to form roughly one Sun-like star every 10,000 years. Star-forming activity has also been spotted in a vast ring of hydrogen gas encircling both Messier 105 and its closest neighbor, the lenticular galaxy NGC 3384.

Messier 105 was discovered on March 24, 1781 by Pierre Méchain. It lies about 30 million light-years away in the constellation of Leo (The Lion), and is the brightest elliptical galaxy within the Leo I galaxy group.

From Wikipedia:

Messier 105 or M105, also known as NGC 3379, is an elliptical galaxy located 36.6 million light years away in the equatorial constellation of Leo. It was discovered by Pierre Méchain on March 24, 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.

This galaxy has a morphological classification of E1, indicating a standard elliptical galaxy with a flattening of 10%. The major axis is aligned along a position angle of 71°. Isophotes of the galaxy are near perfect ellipses, twisting no more than 5° out of alignment, with changes in ellipticity of no more than 0.06. There is no fine structure apparent in the isophotes, such as ripples. Observation of giant stars in the halo indicate there are two general populations: a dominant metal-rich subpopulation and a weaker metal-poor group.

Messier 105 is known to have a supermassive black hole at its core whose mass is estimated to be between 1.4×108 and 2×108 solar masses The galaxy has a weak active galactic nucleus of the LINER type with a spectral class of L2/T2, meaning no broad Ha line and intermediate emission line ratios between a LINER and a H II region. The galaxy also contains a few young stars and stellar clusters, suggesting some elliptical galaxies still form new stars, but very slowly.

This galaxy, along with its companion the barred lenticular galaxy NGC 3384, is surrounded by an enormous ring of neutral hydrogen with a radius of 200 kiloparsecs (650 kilolight-years) and a solar mass of 1.8×109 where star formation has been detected. Messier 105 is one of several galaxies within the M96 Group (also known as the Leo I Group), a group of galaxies in the constellation Leo. The group also includes the Messier objects M95 and M96.