Fluorescent Dark Matter

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Tiassa, Jan 2, 2018.

  1. Tiassa Let us not launch the boat ... Staff Member


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    Because of course it does.

    Why does the Perseus galaxy cluster shine so strangely in one specific color of X-rays? No one is sure, but a much-debated hypothesis holds that these X-rays are a clue to the long-sought identity of dark matter. At the center of this mystery is a 3.5 Kilo-electronvolt (KeV) X-ray color that appears to glow excessively only when regions well outside the cluster center are observed, whereas the area directly surrounding a likely central supermassive black hole is actually deficient in 3.5 KeV X-rays. One proposed resolution—quite controversial—is that something never seen before might be present: fluorescent dark matter (FDM). This form of particle dark matter might be able to absorb 3.5 KeV X-radiation. If operating, FDM, after absorption, might later emit these X-rays from all over the cluster, creating an emission line. However, when seen superposed in front of the central region surrounding the black hole, FDM's absorption would be more prominent, creating an absorption line. Pictured, a composite image of the Perseus galaxy cluster shows visible and radio light in red, and X-ray light from the Earth-orbiting Chandra Observatory in blue.

    Robert Nemiroff and Jerry Bonnell↱ write some challenging paragraphs, but this one is just downright fun. It makes for a great line—Dark matter glows ... because of course it does—that only finds significance because I allowed myself to forget for a moment that if it exists then it radiates°.

    Still, it's a fun moment if you let it be. A video from the Chandra team↱ makes that moment even stranger, because they play up absorption in the typesetting: "A fresh take suggests dark matter particles in the galaxy clusters are both absorbing and emitting X-rays."

    Then again, nothing I've said means anything because apparently the idea of seeing an effect of dark matter in this way is apparently controversial and really hard to explain. That is to say, there must necessarily be some fundamental aspect about the idea of dark matter I am failing to recognize because while I get that we call it dark matter because we can't see it, that just tells me we haven't figured out how to see it. And then, yeah, sure, it becomes a fine joke: Dark matter glows because of course it does.


    ° I also allowed myself to duck a botany joke by correcting the quoted paragraph, because the original copy from Nemiroff and Bonnell used the word "florescent".​

    Chandra X-Ray Observatory. "A Quick Look at the Perseus Cluster". YouTube. 19 December 2017. YouTube.com. 2 January 2018. https://youtu.be/1m7g-DEyTUE

    Nemiroff, Robert and Jerry Bonnell. "Unexpected X-Rays from Perseus Galaxy Cluster". Astronomy Picture of the Day. 2 January 2018. APoD.NASA.gov. 2 January 2018. https://go.nasa.gov/2qbghsa

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