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Messier 105

Messier 105 is the largest elliptical galaxy in the Messier catalog.

Distance

32 million light-years

Apparent Magnitude

10.2

constellation

Leo

object type

Elliptical Galaxy

M105
NASA, ESA, STScI, and C. Sarazin (University of Virginia)

​Messier 105 (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, which includes neighbors M95 and M96 as well as several other fainter galaxies. 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.

The bright-white, diffuse glow of an elliptical galaxy sits at image center. The galaxy's core appears as an intense-white circle that gets more diffuse as you move outward from the core. A rusty-red, diffuse cloud is visible to the upper-left of the galaxy. It extends to the upper-left corner of the image, where it is very faint. Black background dotted with foreground stars and distant galaxies.
It may appear featureless and unexciting at first glance, but Hubble observations M105 reveal that 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, making the system an active galactic nucleus that causes the galaxy’s center to shine far brighter than its surroundings.
ESA/Hubble & NASA, C. Sarazin et al.
M105 (aka NGC 3379)
Hubble peered into the core of M105 (also known as NGC 3379) and measured the motions of stars swirling around its center. These observations proved that a supermassive black hole resides at the galaxy’s heart. According to recent estimates, this black hole could be up to 200 million times as massive as our Sun.
NASA, ESA, Karl Gebhardt (University of Michigan) and Tod Lauer (NOAO)

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, which demonstrated that a supermassive black hole resides at M105’s core.

Best observed in 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.

For more information about Hubble’s observations of M105, see:

locator star chart for M105
This star chart for M105 represents the view from mid-northern latitudes for the given month and time.
Image courtesy of Stellarium

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