in the constellation Leo
38 million light-years
60 million to 200 million times the mass of the Sun
Larger than Earth's orbit around the Sun, but smaller than Jupiter's orbit
Like many of the other galaxies in this directory, M105 (aka NGC 3379) was observed with both Hubble Space Telescope, for a super-sharp view of the galaxy's center, and with ground-based telescopes, for a wider view of the regions farther from the galaxy's core.
The galaxy appears brightest at the center, where the stars are packed most densely, and then gets dimmer towards the edges, as the stars thin out. One particularly interesting aspect of the brightness measurements: computer processing reveals a dark disk in the galaxy's core. This disk probably is made of dust grains that gradually accumulated into circular orbits around the central black hole. The shape of this disk is reminiscent of Saturn's rings, but it's 10 billion times larger!
NGC 3379 is classified as an elliptical galaxy because it appears slightly stretched out in one direction. It might be shaped like a very thick pancake that we're looking at face-on, or like a cigar that we're looking at from the end.
This uncertainty about the galaxy's shape makes it difficult to deduce the mass of the central black hole because the speeds of the stars that orbit the black hole depend on the angle at which we see them. It's like trying to measure the speed of a car with a radar gun without knowing whether the car is moving toward you, sideways, or some angle in between.
As a result, the range of possible masses for the black hole is somewhat larger for this galaxy than for most others; the black hole might be as little as 60 million solar masses, or as large as 200 million solar masses.
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This document was last modified: March 15, 2012.