Posted on 03/25/2010 6:50:58 PM PDT by zeugma
Found: 90% of the distant Universe
This is fascinating news: 90% of the distant Universe was thought to be missing, but it was recently found. And what’s weird is, it was found to be in the red. Quite literally.
[Note: before you ask, this has nothing to do with dark matter. See below!]
GOODS_deepfield
First, a bit of background. Galaxies are filled with hydrogen gas, and that gas is a major component of the clouds that collapse to form stars. When that happens, the hot stars ionize the gas: the flood of ultraviolet light strips the electron away from the proton, freeing both. If the electron gets near the proton again, they can recombine. Because of quantum mechanics, the electron can only exists in certain energy states, which are a bit like steps in a staircase. You can jump from the third step down to the second, but there is no second-and-a-halfth step.
So it is with electrons. It used to be taught that this levels were like orbits, but that’s not a great analogy; the staircase is better. So if the electron is on the second level and drops to the first, it gives off energy in the form of light (just like when you step down you lose a bit of energy too, and it takes energy to go up a step). For the 2 to 1 step in hydrogen, the photon emitted is in the ultraviolet, and has a special name: Lyman alpha.
Ionized hydrogen gas clouds tend to blast out lots of Lyman alpha. This makes it a good way to search for distant star forming regions; just look for that wonderful wavelength of light associated with the 2 – 1 transition of hydrogen.
As it happens, we know that when the Universe was young, about a quarter the age it is now, star formation was going on at a much higher rate on average than it does now. So astronomers figured, hey, why not do searches for distant galaxies using Lyman alpha? They should pump it out, and make them easy to see.
So they looked. And to their surprise, they only found about 10% of the galaxies they predicted they should!
Uh oh.
This has been a problem for some time. But it’s not anymore: a recent experiment by astronomers shows that the galaxies are there, but they’re hidden!
What they did is look in one part of the sky, using the GOODS South field (part of which is pictured above), trying to find Lyman alpha emitting galaxies. Then they looked at the same region, but looked instead for H alpha, the line emitted when an electron jumps down from the third energy level to the second. And guess what they found: tons of galaxies!
The problem, they surmised, is that the galaxies are actually there and emitting Lyman alpha. But before that ultraviolet light can get out of one of those galaxies, it gets reabsorbed by gas inside the galaxy itself. We never see it.
But H alpha can more easily escape the galaxies once it’s produced. For one thing, it’s red light, and that can penetrate the gas and dust better than the ultraviolet Lyman alpha light can. There are other more complicated reasons as well, but the point is, the galaxies were simply hidden from us before, but not anymore. By extrapolating their results, it looks like they found 90% of the distant Universe!
I’ll note: this has nothing to do with dark matter. As it happens, 90% of the matter in the Universe is in a form that emits no light, but affects other matter through gravity. We know it exists, and you can find out why here. We know it exists locally, in nearby galaxies and clusters of galaxies, too. This new result doesn’t affect that, since the now un-hidden galaxies are very far away, like many billions of light years away. They can’t possibly affect nearby galaxies, so they don’t account for dark matter.
I love this study. It’s a great application of simple logic, though it wasn’t so simple to do: they had to use a lot of time on a monster 8 meter telescope to do it! But they were able to answer a question that has been around for some time, and it really does look like they’ve solved it.
And, as always, it makes me wonder what else is lurking out there in space, hidden but for a leap of logic and technology that will allow us to unveil it. Science is all about thinking around problems, and peeking into dusty corners. Sometimes the most interesting things are found there… including, in this case, the vast majority of the Universe!
I guess these things really do come in threes.
Obama's a red, and the solvency of the United States is in the red.
It's always in the last place you put it...
Can't help with the car keys unless you have a cat. Have you asked him/her?
The missing socks, on the other hand, has been explained. From what I understand, the heat and rotational energy from the dryer, combined with the static electricity caused by the clothes tumbling around inside cause a rift in the space-time continuum. Apparently all missing socks end up somewhere on Vogon, which was the real reason they are so gung-ho about building a hyperspace bypass in this neck of the universe.
There is just so much humor waiting to be written about this Thread.
It's going to be a lot of fun to watach.
Spock: “Gas. Gas, Captain. Under impulse power she expends fuel like any other vessel. We call it ‘plasma’. But whatever the Klingon designation is it is merely ionized gas.”
Uhura: “Well what about all that equipment we’re carrying to catalog gaseous anomalies? Well the thing’s got to have a tailpipe.”
—”STVI:TUC”, Stardate 9523.8
bflr
ping
I have 3 cats and I’m missing 3 car keys. Coincidence? I think not!
Put a decent team on the field and I'll tune in on Sundays to watch no matter who the quarterback is. I think we just put too much stock in quarterbacks. They sure do get a lot of undue attention.
Or Obama’s birth certificate. ;-)
You seem to be forgetting how cute Tony Romo’s dimples are.
How was 90% determined if we don’t know what 100% is?
How can they find a finite per-centage of infinity?
I don’t pretend to be scientific minded, just asking.
Does the word “universe” mean “everything”?
The real question is what is on the outside of the universe?
If I put it into words, I’d just be wrong, but that never stops me. From what I understand, the universe we can observe has a finite boundry. According to most, it is also expanding. What it is expanding into, I haven’t clue #1. There would also seem to be a finite amount of “stuff” in the universe. Personally, I’ve never bought into the whole “dark matter” thing, as it just seems like hand-waving and a way to avoid saying “we don’t know”, which seems to be a failure common to most humans.
Orange jello?
Because of the rotational speed of the metal dryer drum cutting magnetic lines of force, which are everywhere,it initiates an obverse minute tear in the space-time continuum through which single socks are able to slip into the Hozone;
thus your missing socks. If you are able to reverse the rotational direction of the metal drum by the square root of 2 you will force your missing socks to return. Thank you for your attention.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.