X-rays From Other Galaxies Could Emanate From Particles of Dark Matter

sciencehabit writes "X-rays of a specific wavelength emanating from the hearts of nearby galaxies and galaxy clusters could be signs of particles of dark matter decaying in space, two independent teams of astronomers report (first study, second study). If that interpretation is correct, then dark matter could consist of strange particles called sterile neutrinos that weigh about 1/100 as much as an electron."

Comments

That's "strange weird" not "strange flavor"

[jfengel]

It took me a second to figure that out. Neutrinos don't participate in the strong force and don't have any flavor. (The names are charming, but kind of annoyingly ambiguous out of context.)

They sure are strange-weird if they don't even participate in the weak force, as other neutrinos do. They're barely there at all (if they ARE there at all).

Re:That's "strange weird" not "strange flavor"

[Anonymous Coward]

I don't understand how something with only 7kEv * c^2 of mass won't be seen already. Even if it shares no property with normal matter, I'd expect it to appear from bare energy + momentum available at accelerators*... Or are people just classifying them as normal neutrinos?

Sterile neutrinos lack the weak interaction of normal neutrinos. The process that allows accelerators and nuclear processes to produce normal neutrinos is through the weak force. In the same way you can't take a photon and turn it directly into a neutrino + anti-neutrino because they don't interact with electromagnetism, you can't take "bare energy and momentum" to produce sterile neutrinos easily in accelerators. More subtle approaches look for them in accelerators, but having a light mass means you need quite a bit of precision to account for missing energy, and a situation distinguishable from say a normal neutrino. Search attempts also involve looking at neutrino oscillations closely, because of various models allowing mixing between normal and sterile neutrinos that could cause them to come up or affect neutrinos emitted from processes that can't emit a sterile neutrino directly.

Re:That's "strange weird" not "strange flavor"

[Anonymous Coward]

Neutrinos don't participate in the strong force and don't have any flavor.

Quarks have both flavour, which defines what type they are, and colour, which defines how they interact with the strong force. Quark flavours are up, down, top, bottom, charm and strange; quark colours are red, green and blue.

Neutrinos do not interact with the strong force, so they don't have colour. But they do come in different varieties, which are (as for quarks) called flavours. The neutrino flavours are electron, muon and tau, corresponding to the type of charged lepton they're associated with. (For example, when you destroy an electron, you have to produce an electron-flavoured neutrino.)

So, you're partly right - neutrinos don't interact with the strong force, but they *do* have flavour.

Interesting Stuff

[rmdingler]

The data they're sorting through is only a 1% bump above the continuum,

but before the shouting about statistical noise begins,

RTFA... it sounds plausible.

Re:Dark matter as likely as ether and phlogiston

[Anonymous Coward]

So can the recently discovered prevalence of "dark worlds", the startling number of planets that are *not* in orbit around a sun, only recently revealed by our best orbital telescopes and their occasional occulusion of other stars. Given such worlds widely spread across entire galaxies of interstellar space, galaxies could easily mass 20% more than expected from pure stellar mapping, which would handily explain most of the anomalies of galactic expansion.

Astronomers working on dark matter theories aren't ignoring that, and in fact were a big push for research into that starting over a decade ago. They expected to see a lot of occlusions to account for dark matter, but did not. The lack of and limited observations of such events sets a clear upper bound on how many such bodies can be in the galaxy and it is way below what is needed to explain rotation curves. The connections you draw to galactic densities and thinking 20% more observed baryonic mass is enough to explain situations suggests you don't really have any clue of the scale of the actual situations. Not only do you need to better examine real data, but you need to more than glance at the headlines as a start.