Fed2 Star - the newsletter for the space trading game Federation 2

The weekly newsletter for Fed2
by ibgames

EARTHDATE: October 22, 2017

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by Hazed

Scientists making models of the universe have known for a while that there is a lot of matter they just can’t find. Much of that is known as dark matter, a mysterious substance which can only be detected thanks to its gravitational pull. But the models also say there should be about twice as much ordinary matter as well: that is, protons, neutrons and electrons.

Now two separate teams have found some of that missing matter – roughly half of it. It is made up of particles called baryons that link galaxies together through filaments of hot, diffuse gas. This gas is very tenuous and it’s not quite hot enough for X-ray telescopes to detect, so up till now nobody had been able to see it.

That means the two teams, from the Institute of Space Astrophysics in Orsay and the University of Edinburgh, UK, had to find another way to show that these threads of gas, which had previously been pure speculation, really did exist.

They did this by using a phenomenon called the Sunyaev-Zel’dovich effect. (Catchy!) This happens when light left over from the big bang passes through hot gas, and some of it scatters off the electrons in the gas, leaving a dim patch in the cosmic microwave background.

The Planck satellite created a map of this effect in 2015, but the dim blotches were too slight be seen directly on the map because the tendrils of gas are so very diffuse. So the two teams stacked up signals for a chosen area between two galaxies, and that made the individually faint strands become detectable.

So that’s half the missing matter found – now what about the other half? And when are we going to find the elusive dark matter?

Source: https://www.newscientist.com/article/2149742-half-the-universes-missing-matter-has-just-been-finally-found

Footnote: when Alan read the draft of this week’s news he commented on this story. Here’s what he said:

Your piece on missing matter seems a little confused about exactly what Baryons are. So....

Baryons are matter which is made up of three quarks. The best known baryons are protons and neutrons.  Baryons are just a category of matter. For the record, the baryon I like the sound of best is called the 'charmed double bottom omega'. No one has ever found one yet, but if I'd known about it when Fed was first written, I would have found some way to put it in!

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