Close-up: Elliptical Galaxy Messier 105 in Leo | Hubble Space Telescope
M105 is an elliptical galaxy 32 million light-years away in the constellation Leo. It is the largest elliptical in the Messier catalog that is not a member of the Virgo cluster of galaxies. M105 does, however, belong to the M96 (or Leo I) Group. This includes neighbors M95 and M96 as well as several other fainter galaxies. M105 is the brightest elliptical galaxy within the Leo I galaxy group.
It might appear featureless and unexciting at first glance, but NASA/European Space Agency 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.
This Hubble image of M105 was taken in near-infrared and visible light. Like most elliptical galaxies it appears rather featureless and inactive. However, Hubble observations surprised astronomers by revealing young stars and star clusters in M105, indicating that star formation is still taking place in what was thought to be a “dead” galaxy no longer capable of giving birth to new stars. Other Hubble observations measured the speeds of stars moving around the center of the galaxy. This demonstrated that a supermassive black hole resides at M105’s core.
Hubble also surprised astronomers by revealing a few young stars and clusters in Messer 105. 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.
Charles Messier’s colleague Pierre Méchain discovered M105 in 1781 just a few days after locating M95 and M96. Yet M105 was not originally included in Messier’s catalog. It was added in 1947 after astronomer Helen S. Hogg found a letter written by Méchain describing the galaxy.
Best observed in the month of April, M105 has an apparent magnitude of 10.2 and can be spotted with a small telescope. Large telescopes will uncover two fainter galaxies (NGC 3384 and NGC 3389) close to the bright elliptical.
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