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isferno
2005-Feb-23, 12:47 PM
In search of Galaxies void of stars, scientists have found a the first Galactic Hydrogen Cloud capable of creating 100 million stars.

Some did object that this might be two hydrogen clouds passing each other giving the effect of rotation redshift, though finding two clouds and just happing to pass each other is much more unlikely.

As found in NewScientist.


What does it contain as blackhole? a once have been runaway star? :D ;)

antoniseb
2005-Feb-23, 02:15 PM
Originally posted by isferno@Feb 23 2005, 12:47 PM
What does it contain as blackhole?
There's no evidence that this object contains a black hole, and it probably doesn't. It is merely a large Hydrogen cloud that hasn't yet had the sort of interaction that would create stars.

Fraser
2005-Feb-23, 05:31 PM
SUMMARY: Astronomers believe that a significant amount of our Universe is made up of mysterious dark matter (5 times more, in fact); it's invisible to every instrument, but can be detected because its gravity affects visible matter. Dark matter is usually found surrounding galaxies in an enormous halo, but British astronomers think they've found a whole galaxy just made of dark matter. The team used a radio telescope to observe the motion of a cloud of hydrogen atoms, and realized that it was spinning much too quickly, so must be largely composed dark matter to hold together.

View full article (http://www.universetoday.com/am/publish/dark_matter_galaxy.html)

What do you think about this story? Post your comments below.

John L
2005-Feb-23, 05:44 PM
I just read this on the BBC News (http://news.bbc.co.uk/2/hi/uk_news/wales/south_east/4288633.stm) website, too. Very cool.

Guest
2005-Feb-23, 05:57 PM
This story was first reported LAST WEEK on the Astronomy.com website (http://www.astronomy.com/default.aspx?c=a&id=2896).

Thomas
2005-Feb-23, 08:12 PM
Dark Matter, I just don’t get it.

"A dark galaxy is an area in the universe containing a large amount of mass that rotates like a galaxy, but contains no stars"
“Dark galaxies are thought to form when the density of matter in a galaxy is too low to create the conditions for star formation.”
“They form a galaxy out of normal matter like trees, hedges and mountains but they don't emit any light.”

Ok it seems clear, Dark Galaxies are just low density galaxies made of ordinary matter like trees, hedges, socks but they don't emit any light.

“Dark Matter is five times more abundant than the ordinary (baryonic) matter that makes up everything we can see and touch.”

Right here is where I get confused. If the quote was “Dark galaxies are thought to be made of ‘dark matter’ the unseen non-baryonic material that makes up the bulk of the galaxy”, I would nod and say ‘I see’. But since I have first heard of dark matter it seems to shift back and forth between “Everything in our awareness, the planets, the stars, even energy, is only an insignificant 10% of the universe. The rest is dark matter, and dark energy.” To a less interesting “Maybe it’s just not glowing”.

Are dark galaxies thought to be made of esoteric non-baryonic matter or just toner?

Thomas

Guest
2005-Feb-23, 08:50 PM
Nowadays, when astronomers say "dark matter," they are almost certainly talking about nonbaryonic matter--subatomic particles that don't interact with ordinary matter. They are usually NOT talking about black holes, brown dwarfs, or puppy dogs.

Here's a quote from an article about this new dark galaxy (http://KenCroswell.com/FirstDarkGalaxy.html), not a press release:


But the cloud's total mass is much greater [than 200 million Suns], implying that, like most galaxies, including our own, it consists primarily of dark matter. Astronomers think dark matter consists of exotic subatomic particles that exert gravitational force but do not otherwise interact with ordinary matter.

Minchin's team estimates the cloud's mass is at least 90 billion Suns. The astronomers reached this conclusion because hydrogen atoms in the cloud move relative to one another at 220 kilometers per second (about half a million miles per hour). If the cloud had less than 90 billion solar masses, its gravity would be too weak to hold on to such speedy atoms.

jamerz3294
2005-Feb-23, 09:33 PM
So, now that we have a Dark Matter galaxy, does this mean that Dark Matter shares other characteristics of regular matter? Since the Dark Matter clumped together, that would imply something about gravity as well...

antoniseb
2005-Feb-23, 09:41 PM
Originally posted by Thomas@Feb 23 2005, 08:12 PM
Are dark galaxies thought to be made of esoteric non-baryonic matter or just toner?
The "galaxy" in this story [the only dark galaxy discovered so far, so generallizations are a little hard to draw], seems to be composed largely of WIMPs, or whatever the non-interacting darkmater is. It does have normal matter in it, but the article said it had less than its share of normal matter.

The article talked about trees, hedges, and socks, but the fraction of normal matter that was observed there was neutral Hydrogen gas. There was no real evidence of stuff heavier than Helium, so there have never been stars there.

One question about this object is how did it get such a high dark matter to normal matter ratio? I'm guessing some larger cloud must have swept up the interacting matter a long time ago.

Guest
2005-Feb-23, 10:13 PM
Originally posted by antoniseb@Feb 23 2005, 09:41 PM

One question about this object is how did it get such a high dark matter to normal matter ratio? I'm guessing some larger cloud must have swept up the interacting matter a long time ago.

Martin Rees speculates that it's because it's spinning so fast. (http://KenCroswell.com/FirstDarkGalaxy.html)

hoarem
2005-Feb-23, 10:19 PM
Fantastic news I thought this would never be cracked.
What an amazing age we live in.

Spritzer
2005-Feb-24, 03:05 AM
How can you tell there is an invisible galaxy if you cannot see it? :huh: I think the plasma theory makes more sense than the dark matter theory. There is no need to add or create things you do not see, cannot prove, etc. :wacko: The plasma theory does not require speculation or guessing.

blueshift
2005-Feb-24, 04:09 AM
Originally posted by Spritzer@Feb 24 2005, 03:05 AM
How can you tell there is an invisible galaxy if you cannot see it? :huh: I think the plasma theory makes more sense than the dark matter theory. There is no need to add or create things you do not see, cannot prove, etc. :wacko: The plasma theory does not require speculation or guessing.
I would rererad the article if I were you..They were very skeptical of their findings and patiently waited for 5 years after sighting it before they drew a conclusion.

blueshift

Svemir
2005-Feb-24, 06:56 AM
They only came to conclusion that this is a galaxy.
What they saw was a huge cloud of fast-spinning Hydrogen gas.
When they say GAS, I always think of atomic Hydrogen and not Hydrogen ions (which is plasma essentially).
So, this is the place to test plasma-cosmology and some aspects of Electric Universe' hypotesis:
It is probably huge plasma-boble with neutral Hydrogen (atomic and molecular) and Hydrogen ions. This is enough to be characterised as quasi-neutral plasma, that is able to conduct electric current and hold the individual atoms/molecules together. Now, from a point of view of plasma/EU cosmology we should see some electric discharges from double layers. We should see some lightnings.

From a conventional point of view, this is very young system with primordial hydrogen and (primordial?) Dark Matter, not dense enough to initiate star formation.
It will be interesting to see some supernovae explosion near by and effects of that explosion on the dark galaxy.

isferno
2005-Feb-25, 11:07 AM
Here is a link to a site with a "looks like" visible star galaxy

link (http://www.abc.net.au/science/news/stories/s1311160.htm)

David S
2005-Feb-26, 10:39 PM
What would have ionized the hydrogen atoms? And if they are inoized, where did all the electrons go? Cause unless the gas can somehow maintain a temperature above 3000K or so (the temp at which gas becomes plasma), the electrons will re-attach themselves to the hydrogen and it will become neutral again.

Also, dark matter is not only detected by how fast the galaxy is rotating. You can also use something called gravitational lensing to measure how massive a galaxy is. The more massive a galaxy cluster is, the more it will bend the light of galaxies behind it. This technique has been used to count up how much dark matter there is in the universe. Since the EM force can't bend light I truely doubt that that is the explination here.

Keith Nealy
2005-Mar-01, 02:29 AM
OK, let's go back for a moment to the earlier question. What sort of dark matter are we talking about? A cloud of hydrogen nuclei is not what I understood to be dark matter. I understood dark matter not to be visible not because it doesn't produce light, but because it's some sort of different animal altogether.

I also thought it was repulsive, not attractive, -connected somehow with dark energy.

How does one define "galaxy" such that you can have a dark matter galaxy that doesn't emit light? Are there dark matter stars? Wouldn't what was inferred be rather a nebula?

What would happen if I drove my spaceship into a dark matter galaxy?

Give us some help here from the experts, please!