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article imageThe Giant That Turned Out To Be A Dwarf

By Sayovi     Mar 8, 2007 in Technology
New data obtained on the apparent celestial couple, NGC 5011 B and C, taken with the 3.6-m ESO telescope, reveal that the two galaxies are not at the same distance, as was believed for the past 23 years.
Galaxies are large systems of stars and interstellar matter, typically containing several million to some trillion stars, of masses between several million and several trillion times that of our Sun, of an extension of a few thousands to several 100,000s light years, typically separated by millions of light years distance. They come in a variety of flavors: Spiral, lenticular, elliptical and irregular. Besides simple stars, they typically contain various types of star clusters and nebulae.
We live in a giant spiral galaxy, the Milky Way Galaxy, of 100,000 light years diameter and a mass of roughly a trillion solar masses. The nearest dwarf galaxies, satellites of the Milky Way, are only a few 100,000 light years distant, while the nearest giant neighbour, the Andromeda Galaxy, also a spiral, is about 2-3 million light years distant.
After many observations by the European southern Observatories, it has come to a conclusion that the two galaxies located towards the Centaurus constellation are not at the same distance. The observations show that NGC 5011C is not a giant but a dwarf galaxy, an overlooked member of a group of galaxies in the vicinity of the Milky Way.
"Our new observations with the 3.6-m ESO telescope thus confirm a new member of the nearby Centaurus A group whose true identity remained hidden because of coordinate confusion and wrong distance estimates in the literature for the last 23 years," says Saviane.
With this new distance determination, the astronomers also established that NGC 5011C lies 500,000 light-years away from the dominant galaxy in its group, Centaurus A. Centaurus A (NGC 5128) is the nearest giant elliptical galaxy, at a distance of about 13 million light-years. It is currently merging with a spiral companion galaxy. It possesses a very massive black hole at its centre and is a source of strong radio and X-ray emission.
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