Map of the Missing Cosmos
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November 07, 2007

Map of the Missing Cosmos

Darkmatterlg_2 The universe is a very complex place; there’s no doubting that. It continually throws up new questions that scientists have to answer, or answers that we just don’t know the question for. One of these questions is where is all the mass?

To better understand what it is that is going on in this article let’s start off with University of Alabama in Huntsville’s own analogy;

Imagine “if billions of lights thought to come from billions of aircraft carriers were found instead to come from billions of extremely bright fireflies.”

This is the analogy that is framing the problem researchers from the University of Alabama Huntsville are facing. The same group of researchers that, back in 2002, announced to the world that they had found a large fraction of the “missing mass” of our universe has, essentially, retracted that statement.

Let’s explain.

The universe must be a certain mass to fit in to one of the three expansion models proposed in the early 20th century. And, with all the research that has been done, scientists have begun to get an idea of just how heavy the universe is (and by heavy, I mean its mass). But there is a difference between what we measure the universe to be, and what we can observably weigh.

In other words, all of what we can see – the gas, dust, planets and stars – don’t add up to the right mass to provide the answer “stable universe.

So “where is all the missing matter?” is question that has been asked for a very long time.

Dark matter is one of those substances that, while unobservable, is believed to add up to fit the “stable universe” equation. But the UAH researchers, in 2002, found what they believed to be another cohabitating answer; heavy x-rays.

Those x-rays allowed scientists to be a little safer in their answers. But all of a sudden the same researchers have announced that, instead of hefty atoms being expelled, the x-ray emitting clouds are emitting tiny electrons.

"This means the mass of these x-ray emitting clouds is much less than we initially thought it was," said Dr. Max Bonamente, an assistant professor in UAH's Physics Department. "A significant portion of what we thought was missing mass turns out to be these 'relativistic' (travelling at the speed of light) electrons."

And though tiny electrons don’t seem to be all that heavy, the sheer amount of them added up to 10% of the mass that is thought to hold the universe together; keeping it from spinning out of control.

The most logical explanation seems to be that a large amount of the energy comes from electrons that are smashing into other photons instead of from warm atoms and ions, which would have recognizable spectral emission lines. "We have never been able to detect spectral emission lines associated with those detections," Bonamente explained. "If this 'bump' in the data were due to cooler gas, it would have emission lines."

But this latest discovery also exposes the problem that, the lighter x-rays they have discovered, may have been “puffing up” the mass of galaxy clusters in the past. Energy used from galaxy clusters – the universes largest object – helped scientists calculate the mass. Now that such energy is connected to light-weight electrons, those measurements drop as well.

Results of this research by Bonamente, Jukka Nevalainen of Finland'sHelsinki Observatory and UAH's Dr. Richard Lieu were published Oct. 20 in the "Astrophysical Journal. So if you manage to get your hands on it, make sure you contact me! I want to know more.

Posted by Josh Hill

Story Links:

Cartoon credits: Thanks to Jeff Rowland, Overcompensating.com

http://www.uah.edu/News/newsread.php?newsID=958
http://www.sciencedaily.com/releases/2007/11/071102152248.htm

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