Milky Way’s Hyperactive Twin

Written by The Night Sky Guy on September 2, 2009 – 11:52 am -

click image to enlarge

click image to enlarge

Astronomers have released a striking new image of a nearby galaxy that many astronomers think closely resembles our own Milky Way. Though the galaxy is seen edge-on, observations of NGC 4945 suggest that this hive of stars is a spiral galaxy much like our own, with swirling, luminous arms and a bar-shaped central region. These resemblances aside, NGC 4945 has a brighter center that likely harbors a supermassive black hole, which is devouring reams of matter and blasting energy out into space.

As NGC 4945 is only about 13 million light-years away in the constellation of Centaurus (the Centaur), a modest telescope is sufficient for skygazers to spot this remarkable galaxy. Today’s new portrait of NGC 4945 comes courtesy of the 2.2-meter MPG/ESO telescope at the LaSilla Observatory in Chile.

NGC 4945 appears cigar-shaped from our perspective on Earth, but the galaxy is actually a disc many times wider than it is thick, with bands of stars and glowing gas spiralinga round its center. With the use of special optical filters to isolate the color of light emitted by heated gases such as hydrogen, the image displays sharp contrasts in NGC 4945 that indicate areas of star formation. Other observations have revealed that NGC 4945 has an active galactic nucleus, meaning its central bulge emits far more energy than calmer galaxies like the Milky Way.

Scientists classify NGC 4945 as a Seyfert type of galaxy which have supermassive black holes that cause the turmoil in their centers. Black holes gravitationally draw gas and dust into them, accelerating and heating this attracted matter until it emits high-energy radiation, including X-rays and ultraviolet light. Most large, spiral galaxies, including the Milky Way, host a black hole in their centers, though many of these dark monsters no longer actively “feed” at this stage in galactic development.

- adapted from a ESO news annoucement


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