First Invisible Galaxy Discovered

**bradybaker** · 02-23-2005 04:25 PM

First Invisible Galaxy Discovered in Cosmology Breakthrough

Wed Feb 23,12:29 PM ET Science - Space.com

Robert Roy Britt
Senior Science Writer
SPACE.com

Astronomers have discovered an invisible galaxy that could be the first of many that will help unravel one of the universe's greatest mysteries.

The object appears to be made mostly of "dark matter," material of an unknown nature that can't be seen.

Theorists have long said most of the universe is made of dark matter. Its presence is required to explain the extra gravitational force that is observed to hold regular galaxies together and that also binds large clusters of galaxies.

Theorists also believe knots of dark matter were integral to the formation of the first stars and galaxies. In the early universe, dark matter condensed like water droplets on a spider web, the thinking goes. Regular matter -- mostly hydrogen gas -- was gravitationally attracted to a dark matter knot, and when the density became great enough, a star would form, marking the birth of a galaxy.

The theory suggests that pockets of pure dark matter ought to remain sprinkled across the cosmos. In 2001, a team led by Neil Trentham of the University of Cambridge predicted the presence of entire dark galaxies.

One of perhaps many

The newfound dark galaxy was detected with radio telescopes. Similar objects could be very common or very rare, said Robert Minchin of Cardiff University in the UK.

"If they are the missing dark matter halos predicted by galaxy formation simulations but not found in optical surveys, then there could be more dark galaxies than ordinary ones," Minchin told SPACE.com.

In a cluster of galaxies known as Virgo, some 50 million light-years away, Minchin and colleagues looked for radio-wavelength radiation coming from hydrogen gas. They found a well of it that contains a hundred million times the mass of the Sun. It is now named VIRGOHI21.

The well of material rotates too quickly to be explained by the observed amount of gas. Something else must serve as gravitational glue.

"From the speed it is spinning, we realized that VIRGOHI21 was a thousand times more massive than could be accounted for by the observed hydrogen atoms alone," Minchin said. "If it were an ordinary galaxy, then it should be quite bright and would be visible with a good amateur telescope."

The ratio of dark matter to regular matter is at least 500-to-1, which is higher than I would expect in an ordinary galaxy," Minchin said. "However, it is very hard to know what to expect with such a unique object -- it may be that high ratios like this are necessary to keep the gas from collapsing to form stars."

Long road to discovery

Other potential dark galaxies have been found previously, but closer observations revealed stars in the mix. Intense visible-light observations reveal no stars in VIRGOHI21.

The invisible galaxy is thought to lack stars because its density is not high enough to trigger star birth, the astronomers said.

The discovery was made in 2000 with the University of Manchester's Lovell Telescope, and the astronomers have worked since then to verify the work. It was announced today.

"The universe has all sorts of secrets still to reveal to us, but this shows that we are beginning to understand how to look at it in the right way," said astronomer Jon Davies of Cardiff University in the UK. It's a really exciting discovery."
Additional radio observations were made with the Arecibo Observatory in Puerto Rico. Follow-up optical work was done with the Isaac Newton Telescope in La Palma. Astronomers from the UK, France, Italy and Australia contributed to the research. The project is now searching for other possible dark galaxies.

Dark matter makes up about 23 percent of the universe's mass-energy budget. Normal matter, the stuff of stars, planets and people, contributes just 4 percent. The rest of the universe is driven by an even more mysterious thing called dark energy.

**Tsen** · 02-23-2005 11:06 PM

Amazing stuff, BradyBaker! To think--About 5 years of research just to confirm it...

The new question is: What applications does the discovery have, on both the scientific, and the every day front?

**baconmastermind** · 02-24-2005 04:35 AM

This leaves me with several questions:
Does dark matter taste better than regular matter?
and
If we can't see it, how will we avoid tripping over it?

**Joseph_Stalin** · 02-24-2005 10:38 PM

Is this when the theists come and laugh at scientists for researching invisible substances?

Very intriguing article, bradybaker.

**Peregrinus** · 02-24-2005 10:48 PM

Originally posted by Joseph_Stalin
Is this when the theists come and laugh at scientists for researching invisible substances?

And the scientists reply that "invisible" does not mean undetectable.

**Howie** · 02-25-2005 05:56 PM

Bradybaker & peregrinus. How did I know I would find you both lurking in this Forum?

If this is of way off the subject Bradybaker, I oppologize and I will move it. But when it comes to space, time, galaxies, dark & anti matter, I somtimes don't know where It fits in .

Anyway. I read a recent article that the outer edges of the universe are expanding at a rate that is actually faster than light. I know it sounds preposterous...
But like the outer edge of a wheel ,The outside edge would go much faster. The outer edge of the universe is expanding at an expotential rate. And supposedly outside this universe is uncharted regions which have no residence. Which give cause for things being able to travel faster than light. And light itself could travel faster than 182,000 miles a second.
I too would guess that time would not exist.?!

What is your take?

**bradybaker** · 02-26-2005 11:12 PM

Sounds similar to the inflationary model of the Big Bang (Google Alan Guth). Basically, it says that there was a period of time (about 10^-15 seconds after the Big Bang) when the universe expanded at an unbelievable rate (faster than light) from the size of a subatomic particle to about the size of a marble.

Some people might initially say, "Hey! That means that Einstein was wrong!". However, those people don't understand what the Big Bang actually was. It was not an explosion in space, but an explosion in which space itself was created.

So, since space itself is expanding, the particles contained in that space are travelling at less than the speed of light, relative to that space. They are only travelling faster than light relative to a region of space that is not expanding (ie. here).

As for what you are saying, it makes sense that the edges of the universe are still expanding and therefore we may observe the particles in that space to be moving faster than light relative to us....but no laws of relavitiy are being broken.

I hope that makes a bit of sense.

**Howie** · 02-27-2005 08:25 AM

Thanks for your comments bradybaker!

Originally posted by bradybaker
As for what you are saying, it makes sense that the edges of the universe are still expanding and therefore we may observe the particles in that space to be moving faster than light relative to us....but no laws of relavitiy are being broken.

That seems contradictory???
When you say - observing relative to us. Does that mean to imply that the particles really are NOT going faster than the speed of light, but appears that way?

**bradybaker** · 02-27-2005 08:59 AM

Pretend you are standing on a train moving at 100mph. You throw a baseball forward at 40mph. Relative to you, on the train, the baseball is moving at a speed of 40mph. However, relative to a stationary observer on the ground, the ball is mvoing at 100 + 40 = 140mph. It's all about your frame of reference.

To an observer running at 10mph beside the train, the ball would be moving at a speed of 130mph relative to them.

In the case of the edges of space, that space itself is the train, the particles are the baseballs and we are the stationary observer.

Originally posted by Howetzer
Does that mean to imply that the particles really are NOT going faster than the speed of light, but appears that way?

They are not going faster than light relative to the space (the train) that they are in. Therefore, no laws of relativity are being broken.

**Howie** · 02-27-2005 09:18 AM

Very well put! Thanks.
However I do remember that the author did state that outside of this universe, because of the fact that even space has some resistance, that this accounts for the reason that these Galaxies can exeed the speed of light.

**Howie** · 02-27-2005 11:40 AM

Originally posted by Howetzer
Very well put! Thanks.
However I do remember that the author did state that outside of this universe, because of the fact that even space has some resistance, that this accounts for the reason that these Galaxies can exeed the speed of light. *

I would like to add some thoughts to my previous post.

From what I understand the closer you go to the speed of light the slower time goes. And the closer you get the more resitance that arises from the mass of the object.
So if our universe is the "train" going at speed that equalls X, then the light inside is going at 186,000 miles a second. This would give the observer (outside of the universe) an observervation of light going at the speed of light + x.
So at that referance point aren't the laws of relativity broken? And if that were true what happens to time

And why don't I try and confuse myself a little more.

**Peregrinus** · 02-27-2005 02:39 PM

This is the expanding balloon analogy of the universe. It's an oldie but goodie.

Imagine you have an expanding balloon. The 3D space of the physical universe is represented by the 2D surface of the spherical balloon. Ants live on this balloon, and they can run really, really fast. Say 186,000 mph is maximum ant speed. As you blow air into the balloon, the skin of the balloon stretches. Even though the ants are running at the same speed of 186,000 mph, as the balloon expands, they are able to run around a smaller fraction of the circumference of the balloon per unit time. At one point in time, they may be able to run all the way around the balloon in an hour, but after a few seconds of expansion, they're only able to make it half way around in an hour, then a quarter of the way around. The "measured velocity" of the ants is still 186,000 mph. If you were standing next to an ant as it raced by, that's the speed you would measure. However, if you're standing a distance away from the ant and watching it run toward you, it will seem to be running slower due to the expansion of the balloon. If the ant were standing still, you'd actually observe it to be receding from your position. If the skin of the balloon is expanding faster than 186,000 mph, then even an ant running at full speed would be seen to move away from you -- that is to say, the "coordinate velocity" of the ant would be negative. Now replace the balloon with the physical universe and ants with photons. This is why we observe a "horizon distance" in the universe. At about 1.3 * 10^9 light years away from us, the universe is expanding so quickly that even the light emitted from those distance sources cannot reach us.

**Joseph_Stalin** · 02-27-2005 07:01 PM

That's some very, very interesting stuff right there. And I must congratulate you on that explanation. That is hands down one of the best "down-to-earth" explanations I've seen in quite a while.

The light will never reach us the rate of expansion...that's what caught my eye the most. Seems quirky, but very logical.

**OpheliaBlue** · 03-02-2005 01:07 PM

Originally posted by baconmastermind
This leaves me with several questions:
Does dark matter taste better than regular matter?

Dark matter tastes the same as regular matter...just has fewer calories.

**baconmastermind** · 03-03-2005 07:58 PM

Originally posted by OpheliaBlue+--><div class='quotetop'>QUOTE(OpheliaBlue)</div>

<!--QuoteBegin-baconmastermind

This leaves me with several questions:
Does dark matter taste better than regular matter?

Dark matter tastes the same as regular matter...just has fewer calories.[/b]

Yeah, I just tried some. I was walking home from school and I tripped over it. I picked it up and drank it, and it really does taste the same.

**nerve** · 03-09-2005 02:20 PM

Originally posted by OpheliaBlue+--><div class='quotetop'>QUOTE(OpheliaBlue)</div>

<!--QuoteBegin-baconmastermind

This leaves me with several questions:
Does dark matter taste better than regular matter?

Dark matter tastes the same as regular matter...just has fewer calories.[/b]

so Dark Matter = Diet Matter?

**Howie** · 03-09-2005 04:46 PM

How can such a good topic go down the shitter so fast?

We all no dark matter taste great but is less filling!

**YourTheManNowDog** · 10-21-2005 07:55 AM

ill believe it when i see it LOL

**Placebo** · 10-24-2005 05:26 AM

As always, if the OP feels that the taste of dark matter discussion has gone too far, he's welcome to PM me to split it into another section

**Oneironaut Zero** · 10-24-2005 09:20 AM

Props to bradybaker for an Very interesting topic, and to Peregrinus for a very well stated explaination.

**Dangeruss** · 10-25-2005 04:32 PM

what a mindfuck. I love this stuff!

I have one question, might be dumb, might be good, but I'll put it out there anyway:

Dark matter is matter that is invisible but has mass and affects light matter galaxies with gravitational pull. Antimatter is matter with the charges switched and the total amount of it should equal the total amount of matter. Both these exotic flavors of matter exist elsewhere in the galaxy.

Is there dark antimatter? It seems like there could be... that there ought to be.

**Tsen** · 10-25-2005 04:54 PM

That's an interesting question. I've still got to do more research on the topic, I'm by no means an expert. Still, I don't know if dark matter classifies as normal matter, so I don't know if it's open to the matter/antimatter law. And there's some speculation that the antimatter/matter balance is tilted to the matter side because of some event or another at the time of the big bang. Don't remember, now I've got to go reread the book again...
It was Lucifer's Legacy, in case any of you want to read as well. It was interesting, mostly talking about symetry (OH MY FREAKIN' GOD. I know I'm a grammar Nazi, but I totally killed that word and I don't know how) Back on topic, it was a pretty good book. Interesting read, at the least.

**TheTruth** · 11-02-2005 02:41 AM

How did the big bang happen, If there was nothing there to start it?

**kimpossible** · 11-02-2005 08:58 AM

Critical Mass

**Oneironaut Zero** · 11-02-2005 09:09 AM

Originally posted by kimpossible
Critical Mass

Could you explain this, further?

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