16-01-11

Dark-Matter Galaxy Detected: Hidden Dwarf Lurks Nearby?

 

Richard A. Lovett in Seattle, Washington


for National Geographic News


Published January 14, 2011

 

Milky Way.jpg

 

Copyright :

http://upload.wikimedia.org/wikipedia/commons/f/fd/Our_Mi...

 

An entire galaxy may be lurking, unseen, just outside our own, scientists announced Thursday.

 


The invisibility of "Galaxy X"—as the purported body has been dubbed—may be due less to its apparent status as a dwarf galaxy than to its murky location and its overwhelming amount of dark matter, astronomer Sukanya Chakrabarti speculates.

 

Detectable only by the effects of its gravitational pull, dark matter is an invisible material that scientists think makes up more than 80 percent of the mass in the universe.

 

Chakrabarti, of the University of California, Berkeley, devised a technique similar to that used 160 years ago to predict the existence of Neptune, which was given away by the wobbles its gravity induced in Uranus's orbit.

 

Based on gravitational perturbations of gases on the fringes of our Milky Way galaxy, Chakrabarti came to her conclusion that there's a unknown dwarf galaxy about 260,000 light-years away.


With an estimated mass equal to only one percent the mass of the Milky Way, Galaxy X is still the third largest of the Milky Way's satellite galaxies, Chakrabarti predicts.


The two Magellanic are each about ten times larger.


If it exists, Galaxy X isn't likely to be composed entirely of dark matter.


It should also have a sprinkling of dim stars, Chakrabarti said.


"These should provide enough light for astronomers to see it, now that they know where to look," she said.


The reason the dark matter galaxy hasn't yet been seen, she added, is because it lies in the same plane as the Milky Way disc.


Clouds of gas and dust stand between us and Galaxy X, confounding telescopes.

 

 

 

Copyright : http://news.nationalgeographic.com/news/2011/01/110114-ga...

 

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