Dark Matter Just Got Darker (and Weirder)

Observations by two powerful space telescopes have revealed that the mysterious stuff that makes up nearly 85 percent of the universe’s total matter is weirder than we ever thought.

VIDEO: Dark Matter: It’s Not A Death Ray

By observing massive colliding galaxy clusters, astronomers have been able to deduce how dark matter behaves during these vast encounters. Until now, we’ve studied a handful of cluster smashups, only allowing us a snapshot of dark matter interactions.

But a new survey by the NASA/ESA Hubble Space Telescope and NASA’s Chandra X-ray Observatory has focused on 72 galactic cluster collisions from all angles and at different times during their collisions. This has given us the unprecedented opportunity to see how dark matter interacts with itself over time.

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> On studying what happens to dark matter during these collisions, the researchers realized that, like stars, the colliding clouds of dark matter have little effect on one another.

I was beginning to suspect as much. But then the puzzle over why dark matter shows no density peak in the centre of our own galaxy becomes even more of a puzzle.

> Next, the researchers want to see whether there is evidence of dark matter particles bouncing off one another like billiard balls.

Excellent idea. I hadn’t thought of that.

> There are still several viable candidates for dark matter

Are there? I don’t know of any, most have already been eliminated to the extent that to make any theory fit the data requires mathematical gymnastics.

mollwollfumble said:

> Next, the researchers want to see whether there is evidence of dark matter particles bouncing off one another like billiard balls.

Excellent idea. I hadn’t thought of that.

How would you look for that?

Sibeen?

The Rev Dodgson said:

mollwollfumble said:

> Next, the researchers want to see whether there is evidence of dark matter particles bouncing off one another like billiard balls.

Excellent idea. I hadn’t thought of that.

How would you look for that?

majiq

The Rev Dodgson said:

mollwollfumble said:

> Next, the researchers want to see whether there is evidence of dark matter particles bouncing off one another like billiard balls.

Excellent idea. I hadn’t thought of that.

How would you look for that?

Good question. One possibility is the following. Each galaxy has its own cloud of billiard balls. After they’ve collided, passed through one another, the billiard balls that have bounced off one another will form a diffuse cloud centred on the impact point. If no such cloud then no billiard-ball-like collision.

mollwollfumble said:

The Rev Dodgson said:

mollwollfumble said:

> Next, the researchers want to see whether there is evidence of dark matter particles bouncing off one another like billiard balls.

Excellent idea. I hadn’t thought of that.

How would you look for that?

Good question. One possibility is the following. Each galaxy has its own cloud of billiard balls. After they’ve collided, passed through one another, the billiard balls that have bounced off one another will form a diffuse cloud centred on the impact point. If no such cloud then no billiard-ball-like collision.

Are we able to detect a diffuse cloud of dark matter?

The Rev Dodgson said:

mollwollfumble said:

The Rev Dodgson said:

How would you look for that?

Good question. One possibility is the following. Each galaxy has its own cloud of billiard balls. After they’ve collided, passed through one another, the billiard balls that have bounced off one another will form a diffuse cloud centred on the impact point. If no such cloud then no billiard-ball-like collision.

Are we able to detect a diffuse cloud of dark matter?

The “new survey by the NASA/ESA Hubble Space Telescope and NASA’s Chandra X-ray Observatory” is hoping to. Every cloud of dark matter, no matter how diffuse, will nicely focus light coming from about twice that distance, and distort galaxy images at other distances. That assumes, of course, that there is something in the way of a galaxy at the necessary location. With a deep enough image, similar to the Hubble ultra-deep field, there will be, but that takes an awful lot of observing time to generate.

I’ve never understood exactly what the computer algorithms are that enable astronomers to generate a density map of dark matter from a distortion of background galaxies, if I was doing it I’d set up a trial and error system – guess the distribution of dark matter and compare the result with observations – but it may be possible to use a deconvolution vaguely similar to the one used in interpreting brain scans.