Dark Matter Mystery Deepens | Space Discussions and Theories | Forum

A A A
Avatar
Please consider registering
Guest
Search
Forum Scope




Match



Forum Options



Minimum search word length is 3 characters - maximum search word length is 84 characters
Register Lost password?
sp_Feed sp_TopicIcon
Dark Matter Mystery Deepens
Avatar
sandra
Member
Members
Forum Posts: 3859
Member Since:
December 4, 2009
sp_UserOfflineSmall Offline
1
October 19, 2011 - 7:28 pm
sp_Permalink sp_Print

Dark Matter Mystery Deepens

ScienceDaily (Oct. 17, 2011) — Like all galaxies, our Milky Way is home to a strange substance called dark matter. Dark matter is invisible, betraying its presence only through its gravitational pull. Without dark matter holding them together, our galaxy's speedy stars would fly off in all directions. The nature of dark matter is a mystery -- a mystery that a new study has only deepened.

"After completing this study, we know less about dark matter than we did before," said lead author Matt Walker, a Hubble Fellow at the Harvard-Smithsonian Center for Astrophysics.

The standard cosmological model describes a universe dominated by dark energy and dark matter. Most astronomers assume that dark matter consists of "cold" (i.e. slow-moving) exotic particles that clump together gravitationally. Over time these dark matter clumps grow and attract normal matter, forming the galaxies we see today.

Cosmologists use powerful computers to simulate this process. Their simulations show that dark matter should be densely packed in the centers of galaxies. Instead, new measurements of two dwarf galaxies show that they contain a smooth distribution of dark matter. This suggests that the standard cosmological model may be wrong.

"Our measurements contradict a basic prediction about the structure of cold dark matter in dwarf galaxies. Unless or until theorists can modify that prediction, cold dark matter is inconsistent with our observational data," Walker stated.

Dwarf galaxies are composed of up to 99 percent dark matter and only one percent normal matter like stars. This disparity makes dwarf galaxies ideal targets for astronomers seeking to understand dark matter.

Walker and his co-author Jorge Peñarrubia (University of Cambridge, UK) analyzed the dark matter distribution in two Milky Way neighbors: the Fornax and Sculptor dwarf galaxies. These galaxies hold one million to 10 million stars, compared to about 400 billion in our galaxy. The team measured the locations, speeds and basic chemical compositions of 1500 to 2500 stars.

"Stars in a dwarf galaxy swarm like bees in a beehive instead of moving in nice, circular orbits like a spiral galaxy," explained Peñarrubia. "That makes it much more challenging to determine the distribution of dark matter."

Their data showed that in both cases, the dark matter is distributed uniformly over a relatively large region, several hundred light-years across. This contradicts the prediction that the density of dark matter should increase sharply toward the centers of these galaxies.

"If a dwarf galaxy were a peach, the standard cosmological model says we should find a dark matter 'pit' at the center. Instead, the first two dwarf galaxies we studied are like pitless peaches," said Peñarrubia.

Some have suggested that interactions between normal and dark matter could spread out the dark matter, but current simulations don't indicate that this happens in dwarf galaxies. The new measurements imply that either normal matter affects dark matter more than expected, or dark matter isn't "cold." The team hopes to determine which is true by studying more dwarf galaxies, particularly galaxies with an even higher percentage of dark matter.

http://www.sciencedaily.com/releases/20 ... 124344.htm

“Living backwards!” Alice repeated in great
astonishment. “I never heard of such a thing!”
“—but there’s one great advantage in it, that one’s
memory works both ways.”
— Lewis Carroll, Through the Looking-Glass

Avatar
kmchenry
New Member
Members
Forum Posts: 1
Member Since:
February 14, 2012
sp_UserOfflineSmall Offline
2
February 15, 2012 - 2:03 am
sp_Permalink sp_Print

Not being an astrophysicist, I'll go out on a limb here. Is it possible the Dwarf Galaxies are Young Galaxies, and are void of a central Massive Black Hole as we find in most spiral galaxies.
Could it be the central black holes tend to concentrate the dark matter and possibly create star forming clouds adding to the galaxies population as it begins to spin and spread?

Forum Timezone: America/Los_Angeles
Most Users Ever Online: 288
Currently Online:
42
Guest(s)
Currently Browsing this Page:
1 Guest(s)
Top Posters:
greeney2: 10318
bionic: 9871
Lashmar: 5290
tigger: 4577
rath: 4298
DIss0n80r: 4162
sandra: 3859
frrostedman: 3816
Wing-Zero: 3279
Tairaa: 2843
Newest Members:
Alexistori Gonzalez
Dhommhee Jang
Elizabeth
Jeff
Rodisco123
Gene
RHJ.Mengerink
Todd
C
Murray
Forum Stats:
Groups: 8
Forums: 31
Topics: 9260
Posts: 124700

 

Member Stats:
Guest Posters: 2
Members: 25023
Moderators: 0
Admins: 2
Administrators: John Greenewald, blackvault