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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."
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.
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!
...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'.
The previous comment is purposely vague and generalized, but all of the facts are completely true.
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.
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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...
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.
Sustainability and energy independence essay