Powerful Galaxies Found in Infrared

demachina writes "NASA's Spitzer Infrared space telescope has discovered 'a mysterious population of distant and enormously powerful galaxies radiating in the infrared spectrum with many hundreds of times more power than our Milky Way galaxy.' They are 80% of the way back to the big bang. They found them by comparing a visible and infrared scan of the sky and looking at the places where there was a big infrared signature and no visible one. They are shrouded in dust."

Comments

Is Dark Matter just hidden matter?

[Kraemahz]

This begs one to ask, if we keep finding these galaxies that are emitting energy but no light, is this dark matter or is it just normal matter that we just haven't been able to find yet? There might be a hell of a lot more dust out there than we thought there was originally.

Re:Is Dark Matter just hidden matter?

[k4_pacific]

Perhaps they are moving away from us fast enough that they are red-shifted completely out of the visible spectrum. Also, there is much speculation that dark matter is normal matter that is not hot enough to emit light.

Re:Is Dark Matter just hidden matter?

[torpor]

or, are we looking merely at reflections of the universe at an earlier period of time, bouncing around the vast distances of space, a kind of 'holographic echo' of time?

sorta, 'earlier reflections of the universe, bouncing around the universe' ..

Re:Is Dark Matter just hidden matter?

[mbrother]

Even among astronomers, nomenclature gets sloppy. I often refer to observations done at 800 or 900 nm as "visible" because we use the same detectors. Light at those wavelengths is almost impossible to actually see. To me, the infrared starts at 1 micron, because that's where you'd switch and use a different instrument with a different dector. The bandgap for silicon corresponds to 1.1 microns, and somewhere close to 1 micron the response falls very low.

You can see what I mean if you have certain types of black and white digital cameras. You can take a picture and see your infrared TV remote light (940 nm) quite clearly.

Re:Is Dark Matter just hidden matter?

[myowntrueself]

A couple of questions

"observation that clusters of galaxies had to have a lot of mass not shining in the visible spectrum in order to be bound objects"

What is the problem here? Does an Oort cloud 'shine'? If the interstellar spaces were crowded with planet-sized bodies, would these 'shine'? Can't this 'missing matter' merely be rocky or icy crud between the stars? I've often suspected that interstellar navigation might be *extremely* dangerous due to such obsticals, but wouldn't they count as 'dark matter'?

"One of the observational lynchpins of the model is its set of predictions for light element abundances."

So is this setting a limit on how 'crowded with crap' the interstellar medium could be? And if we discover that its thicker than this, then relativity is in trouble?

"it was discovered that the space between galaxies in clusters is filled with a 10-100 million degree gas (well, plasma) known as the intracluster medium or ICM"

Ok so suppose one were in a spacecraft in one of these clouds of 'plasma' and one stuck a thermometer out of the hull, would it *really* show such a high temperature? Would it not be a cold 'vacuum' out there... even thinner and colder than the 'vacuum' of our own solar system?

Or is the high temperature somehow taken as an aggregate temperature for a large volume of space with small quantities of gas particles or ions whizzing about at extremely high speed and therefore the point temperature at any given location in that cloud would actually be quite low?

Re:Is Dark Matter just hidden matter?

[mbrother]

That's right. There's just not much stuff out there. The chances would be tiny.

The one caveat to this concerns the speed of the spaceship. If it approaches relativistic speeds, a pebble can hit like a mountain. In this situation, you'd want to have some kind of active shielding. I describe one such system in my novel Star Dragon, which is out in paperback or available from my website for free download.

Re:Is Dark Matter just hidden matter?

[benmcgruer]

We have very good limits on the Oort cloud density

Really? By very good you mean within multiple orders of magnitude - with lots of hand waving. No one can even agree on the method used to perturb comets from the Oort Cloud into visible orbits, so the statistics are more like guesses. We're only working with a sample space of ~50 comets that have been observed and quantified in all of human history, hardly something that you can base sound stats on. As far as I'm aware the current estimates for Oort Cloud densities vary from 10 earth masses to 1000's of earth masses. And with no hope of being able to observe the Oort Cloud any time in the near future, I'd say the estimates are far from very good.

The Oort Cloud itself is far from a certainty - the theory relies on the existence of another unobservable Inner Oort Cloud which periodically replenishes the Outer Oort Cloud. The density of this inner cloud can only be estimated based on our very poor knowledge of the outer cloud.

I'd say we're a long way from a very good understanding just yet.

Something i have always wondered

[X0563511]

If all the stars and celestial bodies (galaxies, ect.) are all different distances from us, and are all moving in relation to each other...

How do we know where they really are? If any EM radiation takes time to get here... Our night sky view is a view of something that has never happened, is not happening now, and will not happen (at least the particular configuration we see). The same thing goes for our radio telescopes, thermal, x-ray, ect.

That galaxy they found could not even exist now, or it may actually be 180 degrees relative to where we see it now.

Am i just crazy? Or do we have NO hope of actually figuring out where things are unless we figure out how to use quantum mechanics somehow to do it?

Re:Something i have always wondered

[Jim Starx]

The math is actually not beyond us. There have been some very interesting results using ray tracing to simulate what the surroundings would look like if you were to be accelerated to a relativistic speed.

See here and here.

It's kind of wierd to think

[Sheetrock]

About how much space we've mapped and yet... no life appears to be out there. The odds would have you thinking otherwise (given an infinite universe) but nothing found.

Maybe we're just in a particularly lucky section of the Big Bang spew. Or maybe we can't observe light that far away because of gravitational effects on photons. Kind of makes you wonder if it's by design.

Re:Damn pop-ups

[The Hobo]

I've noticed something about sites that people say have popups. I go to these sites, and twice now, I see something similar to this. Notice I made the box on the top left. That's the FlashBlock symbol, which blocks all flash elements on web pages and replaces them with that symbol until you click on them. If I click on the symbol, I get the popup. Therefore, I say a possible way to stop these new popups, for now, is to use FlashBlock. It allows you to have flash installed while avoided flash ads, since most of the websites you visit don't use flash except for ads, and the ones that do have flash content you want you just click on the icon.

galaxies full of dyson spheres?

[Anonymous Coward]

a dyson sphere is said to only radiate infrared. wiki

Re:Large Blobs of Heat?

[mbrother]

There are presumably stars in there, mostly obscured by dust. And likely quasars/actic galactic nuclei. Admittedly, there is speculation here, but educated speculation. What is known is the redshift, the energy flux, which together give us the distance and luminosity. The luminosities are huge -- only galaxies have such huge luminosities. Only massive starbursts or quasars could power these objects. Quasars seem to exist only in the centers of massive galaxies. Ergo, we must have galaxies filled with stars. Also, the dust redenning means there's a lot of dust present, and it takes certain kinds of stars to make dust. Ergo, there are a lot of stars there.

As I said, speculation, but educated speculation. Not a big leap of faith in the arguments above.