Astronomers Find Star-Less Galaxy

Wohngebaeudeversicherung writes "Astronomers have discovered a galaxy about 50 million lightyears away from earth that appears to be composed entirly of dark matter. This galaxy, dubbed VIRGOHI21 is rotating like a real galaxy, at speeds only explainable through massive amounts of matter, thought no single visible star could be detected."

Comments

Re: Dark matter is sciences god

[Black Parrot]

> ark matter is just another word for "we have no idea"

I think you meant to say that you have no idea.

Re:Dark Matter

[Agent Orange]

They observed the neutral hydrogen gas (HI), which emits radio waves at the well-known 21cm wavelength. This is not dark at all. From the rotation of the gas, we can work out, with a few assumptions, how big the gravitational potentional would be required in order that the gas is bound. This extra mass is assumed to be dark matter.

Re:Black holes?

[ajs]

There are a few mistakes in your conjectures. First off, we're not talking about "a star". You would most likely not be able to make out a single star in such a remote galaxy unless it were astoundingly bright.

What this tells us is that the density of visible stars in that galaxy (assuming a normal distribution of magnitudes) is low enough that we cannot detect any of them. Someone else care to do the math and tell us what that density threshold is?

When you see "stars" in distant galaxies like Andromeda, what you're really seeing are clusters of stars, though perhaps modern technology has allowed us to resolve single very bright stars, I'm not sure.

As for something blocking our view... that's unlikely, as the dark galaxy was detected by viewing its hydrogen signature in radio wavelengths, so there's no problem seeing it in the correct wavelength.

Most likely (my untrained opinion), this is a galaxy composed of either very small stars or very old (burned out) stars. I'm sure there are good models for describing either. In the first case, for example, I would think that a low initial density of stellar material (mostly hydrogen) would lead to the formation of smaller-than-average stars.

What I think this observation proves is that galactic magnitudes can dip below our viewing threshold in the visible spectrum, and therefore any estimates of the mass of the universe based on visual surveys can be discounted. This makes the closed theory of universal expansion far more likely (e.g. that the universe will expand to a certain point, and then begin to contract until it collapses back into a singularity from which a new Big Bang would arise).

Ok, real astronomers ready your red ink! ;-)

Re:Anyone Question the Existence of Dark Matter?

[Kainaw]

...our understanding of gravity, which has worked extremely well for us for hundreds of years...

Keep in mind that our understanding of gravity is that we have no clue what it is. However, our understanding of the effect of gravity has been working fine. The effect of gravity and gravity are two different things. It could very well be that there is absolutely no such thing as gravity and the effect of gravity is actually a side-effect multi-dimensional distortion, or subatomic radiation, or pure heavenly magic. That is why there is a 'theory of gravity' and a set of 'laws of the force of gravity'.

Re:I like the picture

[franl]

What got me about the picture was the amount of stars visible BEHIND the supposed dark matter galaxy.

The thing is 50 million light years away. The stars you see in the picture are in our galaxy, and thus in the foreground. The only things you would see behind it are normal galaxies.

Re:Black holes?

[The_REAL_DZA]

Still seeing only "clusters" of stars? Check out this view from our old friend Hubble!

This image and the TERAbytes of data like it that have been collected over such a short time are testimony to why losing Hubble is going to be such a tragedy -- whether or not we understand or accept the reasons it's going to happen.

Re:Dark matter is sciences god

[Jussi K. Kojootti]

Isaac Newton and whole host of other Giants in the world of Science would most certainly disagree.

Well, sure. A lot of them would also have been thrown in jail if they would have done anything else... If you have a reference for that school of thought that says without Christianity a lot of Scientific discoveries would have been a really late in coming, I'd like to see it. Not trying to annoy you, I'm just curious.

[Christianity is] largely respobsible for driving out superstion in a lot of cultures.

May I rephrase: "Christianity is largely responsible for replacing a lot of superstitions with other ones".

I'm sorry if I sound aggressive. I'm not dismissing the idea of the supremacy of Christianity as an ideology altogether, I just find it very, very arrogant that someone would support that without extremely good scientific proof.

The grandparent didn't express his views with good manners, I'll give you that - but the core idea of his post is still true: The church has through the years made up 'truths' and tried suppress scientific research that tests those 'truths'. Isaac Newton or other christian scientists might have believed in the scientific method, but it seems that the church as an entity does not...

Energy is conserved

[Engineer-Poet]

A galaxy full of Dyson spheres would be radiating the same amount of energy, but in the IR. If that was the case, Keck would see it glowing merrily away.

What I find most interesting about the "dark galaxy" is that it's got plenty of hydrogen but it somehow has not managed to form stars.

Re:Dark matter is sciences god

[phyruxus]

>>It kills me how people seem to think religion means an automatic closed mindedness.

The problem isn't that everyone who is religious has a closed mind; there are religious people with open minds (even more now that it won't get your burned for heresy). The problem is that some people, who are *very* closed minded use religion as an excuse to believe- or not believe - arbitrary things. I can't say for sure whether these bottom of the barrel "I'm right no matter what" types are products of religion or are merely drawn to it, but I can say that they annoy me, that they fester unchecked in many places, and that they successfully supplant knowledge of reality with fantasy and falsehood to further their agendas.

>>That'a matter for discussion but Religion most certainly does not mean an automatic close minded approach.

True enough in an academic sense, but in the US at least, church and politics are closely tied, and "faith" is frequently used to close people's minds to one thing and/or focus their minds on another thing. I'm not by this saying that religion exists only for that purpose (real religion is imho not about that) but that in practice, it happens, and in my experience, a lot all the time.

>>There is even a school of thought that says without Christianity a lot of Scientific discoveries would have been a really late in coming. Since it's largely respobsible for driving out superstion in a lot of cultures.

Drove out superstition? So, leprechauns are superstition, but angels aren't? Looks to me like christianity replaced one superstition with another. Christianity may (for the sake of argument) be a more advanced form of superstition than faeries and elves and dwarves, but it's still not literal. One may be able to "interpret" religion to find guidance with your life, but the literal view is blatantly superstitious. How is one god better than 10? How are two magical, hidden worlds more real than ghosts walking this world? Sorry to have to ask you that, but I find it outrageously foolish to state that today's religion is less absurd than yesterday's just because the flavor changed.