Posted on 02/23/2008 9:47:44 PM PST by LibWhacker
The first stars to appear in the Universe may have been powered by dark matter, according to US scientists.
Normal stars are powered by nuclear fusion reactions, where hydrogen atoms meld to form heavier helium.
But when the Universe was still young, there would have been abundant dark matter, made of particles called Wimps: Weakly Interacting Massive Particles.
These would have fused together and obliterated each other long before nuclear fusion had the chance to start.
As a result, the first stars would have looked quite different from the ones we see today, and they may have changed the course of the Universe's evolution - or at least held it up.
The theory, published in the journal Physical Review Letters, depends on particles that astronomers can't see, but are certain exist, and physicists have never detected. But the indirect evidence for their existence is overwhelming.
"Dark matter particles make up more than three-quarters of the mass of the Universe," says theoretical physicist Katherine Freese from the University of Michigan.
"In fact, billions of them are passing through each of us every second."
In the early Universe, there would have been even more.
Changing course
The nature of the first stars has long puzzled astronomers. Immediately after the Big Bang, the Universe expanded and cooled, so that for millions of years it was filled with dark, featureless hydrogen and helium - and perhaps Wimps.
Astronomers can see that there were normal stars 700 million years after the Big Bang - the Hubble Telescope looking to the edges of the Universe, which is like looking back billions of years in time, can see whole galaxies of them.
But how did the Universe change course?
The leading theory is that gravity pulled balls of dark matter and hydrogen together.
"These 'haloes', as we call them, are about a million times as massive as the Sun, and the first stars formed inside their centres," Professor Freese told the BBC.
It had been thought the hydrogen brought together by these dark matter haloes would collapse to make the first small stars, and would start to make inside themselves the first new elements - carbon, oxygen, silicon and other materials needed by planets and life.
But the new paper says reactions between the Wimps, colliding and annihilating each other, would have generated enough heat to keep the protostars inflated - like hot air balloons. And as more Wimps rained down on them the heating would have kept going.
These giant, diffuse stars could have filled the orbit of the Earth.
The details of what the stars would have looked like have yet to be worked out. But in five years' time, Nasa will be launching its James Webb Space Telescope (JWST), the successor to the Hubble Space Telescope, and that might be able see right back to these "dark" stars.
There is also the intriguing possibility, says Professor Freese, that in some corner of our local Universe, there may be a few survivors lurking unnoticed.
Once, I bit into a cookie expecting it to be a Chocolate Chip cookie. It was a Raison cookie.
I’m still not over it.
Our measurements don’t coincide with reality. Our theoretical basis cannot be wrong so we just make stuff up. Great.
Sounds like the Obama campign.
I am a physicist by no scope of anyone’s imagination. I do agree there is dark matter all around our planet and on our planet for when I look into space, I see matter. I do not understand the terminology but if I remember correctly, Einstein did say gravity was so insignificant as to be negligible. My opinion is, should Einstein have been correct, there appears a portion of gray matter missing from today’s path taken by many of our scientists and physicists. Dark matter, I agree, makes up more than a significant portion of the universe. But from my perspective, the dark matter is significantly more abundant than matter, perhaps on a ratio of 10,000,000,000 to one or greater. The physicist’s observations appear less than accurate, but by no scope of the imagination am I a physicist.
I wonder if any of these scientists are atheists. Parallels with religious faith are striking to me.
Gotta love a theory that predicts you can’t observe any evidence for it ...
http://www.youtube.com/watch?v=gCgTJ6ID6ZA&feature=related
Sincerely, and May the Blessings of Freedom Long Endure,
Way over my head, but interesting. *grin*
Sith Rule!! Even back then...
Science Fiction today can say anything they want to, no need to back it up with evidence or proof. Those things just get in the way of grant money. I say the first stars were not just dark, they were inside out as well. Anyone wish to fund a study? I’ll need a few million $ to think about this more...
My favorite space-spoof! DARK STAR!
I'm afraid nothing, unfortunately. Lots of people are joking around, which is fine by me. I do it myself. But, otoh, there is a small contingent of Freepers that despises science and scientists. I feel sorry for them. They never had the opportunities God gave the rest of us to study science and learn about how the world works. A person needs that in order to perceive His Creation with some small sense of the awe and appreciation it deserves, and which only comes with knowledge and understanding.
They're good people. I do believe that. They just don't know what they're missing.
I don't think it's the dark matter that's in question, more like the "can't see but are certain exist" and "indirect evidence for their existence" parts that are being commented on.
It's the same kind of thing I see creationists and ID'ers criticized for; believing that something exists without solid, physical evidence.
From JasonC answering a question on "event horizons":
The term event horizon refers to the boundary region around a black hole within which gravity is so strong even light cannot escape. Events within that horizon are thus barred from interacting with events outside it, as no signal can travel outward successfully (up to a quibble about quantum effects right at the boundary).
JasonC discusses "First Light"
What you are thinking of is the epoch when the universe became transparent. Originally theory says it was a plasma - like a fireball, all particles "ionized" or in other words stripped of their electrons which fly around free themselves - which would not transmit light, since any photon would collide with something (usually one of the electrons) before getting far, and be scattered again.
That is as far back as one could theoretically "see" in time with "old light", because light earlier than that couldn't travel. Once the universe cools enough that electrons are captured by atoms, it becomes transparent to light, and light emitted from that point on might reach us now, if it started far enough away.
The cosmic microwave background radiation - a diffuse, nearly uniform microwave "hum" seen in all directions, at an absolute temperature of 3 degrees kelvin worth of energy, is thought to be the afterglow of that epoch, or the "first light" that could get to us now. Not that there wasn't any earlier, but it would have been totally scrambled by multiple absorptions and re-emissions (aka collisions or scatterings) in the plasma etc.
This is usually called the epoch of transparency or something similar, but not "event horizon".
700 million years is long after it is thought to have occurred, though.
The distance between all objects is increasing with time. The farther apart they are, the faster this "runs". Space itself is expanding. We conclude this because in every direction we look, distance objects are receding from us, which we can tell because the light from them is shifted toward the red end of the spectrum (longer wavelength). This is the same doppler effect that changes the sound pitch as a train goes by - you can tell by the sound difference whether it is approaching or receding.
We can measure whether light from distant stars is redshifted or blueshifted, because different atoms emit definite spectral lines in a clear pattern. If you line up the pattern seen in a lab from e.g. glowing hydrogen, with the pattern seen from a distant star, they are the same distance apart and the same line widths, but all moved toward red by the same amount. Ergo, that star is moving away from us, at a velocity we can measure by how much the light-pattern moved.
For nearby objects, some are redshifted and some are blueshifted, because they all have "proper motions" toward or away from us. But go far enough away, and there aren't any objects headed toward us anymore. Everything is receding, and faster and faster the farther it is away.
One might imagine this is because we are smack at the center of everything, and everything is specifically moving away from this one and only spot, at higher and higher speeds, because gosh nothing wants to be here.
But scientists don't accept explanations that "ad hoc". The other possible conclusion is that anywhere you are, you'd see that - because space itself is expanding. That is the current accepted theory, to explain the red shift seen in the color spectra of distant objects.
JasonC explains the conceptual "historiscope"
Here is another related one I quite like, from a writer named Harry Mulisch. It is the idea of an "historiscope". Since as we look farther away, we are looking backward in time, the idea is to exploit this to look backward in time right where we are, aka to literally see our own history. All it would require is something shiny and reflective enough at a great enough distance, combined with a powerfully enough telescope to see the reflection.
Imagine a giant mirror 1000 light years away, directly aligned to face us, and a monster telescope array the size of a whole solar system or something similar. Focus the telescope on the mirror. Then the light impacting the telescope this instant, will be photons that left the mirror 1000 years ago. But some of those are photons that left earth 1000 years before *that*, travel to the mirror for a thousand years, hit it and bounced, and have now spent another thousand years on the return journey. So as you looked in the mirror, you would literally see the earth 2000 years ago.
The beautiful thought involved in this is that the past is not gone. Information about it is streaking off into space at the speed of light, and bouncing in ripples off everything it touches, and some of those ripples can come right back here. The past is in principle directly observable. Not just the light years distant, astronomical past, but in principle even local happenings.
Of course the practicalities of actually exploiting this are daunting. Very few photons hit any given object a long way away, most things aren't that shiny and aren't aligned, few of the scattered photons come back to any local detector, etc. But the principle of the thing is still mindblowing, in my humble opinion, and indescribably beautiful.
Told you I saved these, Jason - lol! : )
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