APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Comments and questions about the APOD on the main view screen.
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APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by APOD Robot » Tue Jan 02, 2018 5:05 am

Image Unexpected X-Rays from Perseus Galaxy Cluster

Explanation: 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: flourescent 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.

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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by Ann » Tue Jan 02, 2018 8:22 am

From my amateur viewpoint of ignorance, I must ask:

The X-rays appear to be centered on Perseus A, NGC 1275. NGC 1275 consists of a large elliptical galaxy and a smallish spiral galaxy that is colliding with it. We are talking about a titanic cosmic collision, which is likely driving a lot of gas and dust into the central black hole of Perseus A.

So, isn't it possible that the X-rays are another product of this collision and the consequent goings-on at the feeding supermassive black hole?

Ann
Last edited by Ann on Tue Jan 02, 2018 10:03 am, edited 1 time in total.
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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by moonshadow1 » Tue Jan 02, 2018 9:52 am

Check the spelling of fluorescent.

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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by moontrail » Tue Jan 02, 2018 10:21 am

Maybe the explanation would be more readable in a two columns format. It's difficult for me sometimes to read it in the one column format.

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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by rstevenson » Tue Jan 02, 2018 2:38 pm

moontrail wrote:Maybe the explanation would be more readable in a two columns format. It's difficult for me sometimes to read it in the one column format....
There have been previous suggestions to update the APOD page code, in part for exactly this reason, to make it more readable on a greater variety of screens and for a greater variety of humanoids. But so far, there's been no movement in this direction. I even worked out sample page code a few years ago, to no avail. The keepers of the APOD flame have their reasons, of course, for leaving it as is.

It's possible to use a custom style sheet for individual web sites, if it's worth the bother to you to set one up. I tried it once, but didn't find it all that helpful or easy to use, and the browser add-on that made it happen didn't survive a later system and browser update.

A quick fix that you might find useful: temporarily narrow the page (the entire browser window) as far as required. The text will narrow along with the page, of course.

[edit]
I just downloaded and installed Stylish, a popular add-on for customizing your view of particular sites. It served to remind me why the APOD page needs some rebuilding, even to make it possible to sensibly customize the style for your own viewing needs. The page has effectively no modern structural elements in it, so it's nearly impossible to re-position or style in other ways any of its content elements independently of any other element. For example, it was easy to shrink the description paragraph's width, but it hugged the left page edge. Applying a margin to push it over inexplicably pushed over and shrank the image above it. And so on.

Rob
Last edited by rstevenson on Tue Jan 02, 2018 3:10 pm, edited 1 time in total.

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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by BDanielMayfield » Tue Jan 02, 2018 3:04 pm

Ann wrote:From my amateur viewpoint of ignorance, I must ask:

The X-rays appear to be centered on Perseus A, NGC 1275. NGC 1275 consists of a large elliptical galaxy and a smallish spiral galaxy that is colliding with it. We are talking about a titanic cosmic collision, which is likely driving a lot of gas and dust into the central black hole of Perseus A.

So, isn't it possible that the X-rays are another product of this collision and the consequent goings-on at the feeding supermassive black hole?

Ann
A very reasonable question Ann. Wouldn't such an ordinary, simple explanation like what Ann has come up with need to be ruled out before calling up a heretofore unheard of explanation like fluorescent dark matter?

Bruce
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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by Joules » Tue Jan 02, 2018 3:06 pm

Practically a Yin-Yang.
The lack of fine structure is remarkable, and exactly what you'd expect for non-collisional particles.

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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by bystander » Tue Jan 02, 2018 3:11 pm

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alive to the gentle breeze of communication, and please stop being such a jerk.
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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by Chris Peterson » Tue Jan 02, 2018 3:20 pm

Ann wrote:So, isn't it possible that the X-rays are another product of this collision and the consequent goings-on at the feeding supermassive black hole?
I believe the problem comes from the fact that the x-rays appear only at a narrow wavelength, like an emission source. The x-rays produced by thermal sources like collisions are broadband, looking like blackbody or graybody emission. The narrowband source suggests a different sort of underlying physics. (My initial guess would have been a natural x-ray laser, but this isn't an area I know much about.)
Chris

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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by BDanielMayfield » Tue Jan 02, 2018 4:11 pm

Chris Peterson wrote:
Ann wrote:So, isn't it possible that the X-rays are another product of this collision and the consequent goings-on at the feeding supermassive black hole?
I believe the problem comes from the fact that the x-rays appear only at a narrow wavelength, like an emission source. The x-rays produced by thermal sources like collisions are broadband, looking like blackbody or graybody emission. The narrowband source suggests a different sort of underlying physics. (My initial guess would have been a natural x-ray laser, but this isn't an area I know much about.)
Ah, an unknown narrow emission makes the seek for a new physical source much more reasonable.
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axinte

Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by axinte » Tue Jan 02, 2018 4:15 pm

moonshadow1 wrote:Check the spelling of fluorescent.
I come here to say the same.
Funny thing it was ”corrected„ not on the web page but here on the copy text. florescent was corrected with flourescent. You can delete this after correction is done

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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by neufer » Tue Jan 02, 2018 4:16 pm

Chris Peterson wrote:
Ann wrote:
So, isn't it possible that the X-rays are another product of this collision and the consequent goings-on at the feeding supermassive black hole?
I believe the problem comes from the fact that the x-rays appear only at a narrow wavelength, like an emission source. The x-rays produced by thermal sources like collisions are broadband, looking like blackbody or graybody emission. The narrowband source suggests a different sort of underlying physics. (My initial guess would have been a natural x-ray laser, but this isn't an area I know much about.)
The hydrogen Lyman-alpha UV line: 121.567 nm = 3/4 Rydberg constant = 10.2 eV
represents (essentially) the highest energy hydrogen line.

For silicon this would correspond to ~ 2 keV = 142 x 10.2 eV
For iron this would correspond to ~ 6.9 keV = 262 x 10.2 eV

Iron is probably the only atom abundant enough to produce strong X-ray lines in the 3.5 keV region.
https://en.wikipedia.org/wiki/NGC_1275 wrote:
<<NGC 1275 corresponds to the radio galaxy Perseus A and is situated near the center of the large Perseus Cluster of galaxies. NGC 1275 consists of two galaxies, a central type-cD galaxy in the Perseus Cluster, and a so-called "high velocity system" (HVS) which lies in front of it. The HVS is moving at 3000 km/s towards the dominant system, and is believed to be merging with the Perseus Cluster. The HVS is not affecting the cD galaxy as it lies at least 200 thousand light years from it. however tidal interactions are disrupting it and ram-pressure stripping produced by its interaction with the intracluster medium of Perseus is stripping its gas as well as producing large amounts of star formation within it>>
Hydrogen gas proton rest mass = Mc2= 938 MeV
Proton kinetic energy (3000 km/s) = Mv2/2 = 938 MeV (.01)2/2 = ~ 47 keV

Ergo: Ram-pressure stripping of iron atoms by (abundant) hydrogen gas could provide the energy source.
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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by RJN » Tue Jan 02, 2018 7:11 pm

moonshadow1 wrote:Check the spelling of fluorescent.
Thank you. I have now corrected the spelling of "fluorscent" on the main NASA APOD. After pointed out by an emailer, I also lower-cased the "k" in keV. I apologize for the oversights.

- RJN

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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by Chris Peterson » Tue Jan 02, 2018 7:20 pm

neufer wrote:Ergo: Ram-pressure stripping of iron atoms by (abundant) hydrogen gas could provide the energy source.
I think the problem is that such a mechanism doesn't explain the nature of the observed spectrum. While there are well understood processes that result in x-ray emission lines, those lines exist against a continuum, and multiple lines are present. It seems like what we have here is a monochromatic source.
Chris

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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by neufer » Tue Jan 02, 2018 7:23 pm

RJN wrote:
moonshadow1 wrote:
Check the spelling of fluorescent.
Thank you. I have now corrected the spelling of "fluorscent" on the main NASA APOD. After pointed out by an emailer, I also lower-cased the "k" in keV. I apologize for the oversights.
https://en.wikipedia.org/wiki/Inflorescence wrote:
<<An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed. The modifications can involve the length and the nature of the internodes and the phyllotaxis, as well as variations in the proportions, compressions, swellings, adnations, connations and reduction of main and secondary axes. Inflorescence can also be defined as the reproductive portion of a plant that bears a cluster of flowers in a specific pattern.
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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by BDanielMayfield » Tue Jan 02, 2018 7:25 pm

neufer wrote:
Chris Peterson wrote:
Ann wrote:
So, isn't it possible that the X-rays are another product of this collision and the consequent goings-on at the feeding supermassive black hole?
I believe the problem comes from the fact that the x-rays appear only at a narrow wavelength, like an emission source. The x-rays produced by thermal sources like collisions are broadband, looking like blackbody or graybody emission. The narrowband source suggests a different sort of underlying physics. (My initial guess would have been a natural x-ray laser, but this isn't an area I know much about.)
The hydrogen Lyman-alpha UV line: 121.567 nm = 3/4 Rydberg constant = 10.2 eV
represents (essentially) the highest energy hydrogen line.

For silicon this would correspond to ~ 2 keV = 142 x 10.2 eV
For iron this would correspond to ~ 6.9 keV = 262 x 10.2 eV

Iron is probably the only atom abundant enough to produce strong X-ray lines in the 3.5 keV region.
https://en.wikipedia.org/wiki/NGC_1275 wrote:
<<NGC 1275 corresponds to the radio galaxy Perseus A and is situated near the center of the large Perseus Cluster of galaxies. NGC 1275 consists of two galaxies, a central type-cD galaxy in the Perseus Cluster, and a so-called "high velocity system" (HVS) which lies in front of it. The HVS is moving at 3000 km/s towards the dominant system, and is believed to be merging with the Perseus Cluster. The HVS is not affecting the cD galaxy as it lies at least 200 thousand light years from it. however tidal interactions are disrupting it and ram-pressure stripping produced by its interaction with the intracluster medium of Perseus is stripping its gas as well as producing large amounts of star formation within it>>
Hydrogen gas proton rest mass = Mc2= 938 MeV
Proton kinetic energy (3000 km/s) = Mv2/2 = 938 MeV (.01)2/2 = ~ 47 keV

Ergo: Ram-pressure stripping of iron atoms by (abundant) hydrogen gas could provide the energy source.
Then I will recycle my earlier comment re Ann's question:
BDanielMayfield wrote:A very reasonable question Ann solution Art. Wouldn't such an ordinary, simple explanation like what Annrt has come up with need to be ruled out before calling up a heretofore unheard of explanation like fluorescent dark matter?

Bruce
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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by neufer » Tue Jan 02, 2018 7:49 pm

Chris Peterson wrote:
neufer wrote:
Ergo: Ram-pressure stripping of iron atoms by (abundant) hydrogen gas could provide the energy source.
I think the problem is that such a mechanism doesn't explain the nature of the observed spectrum. While there are well understood processes that result in x-ray emission lines, those lines exist against a continuum, and multiple lines are present. It seems like what we have here is a monochromatic source.
I'm not dismissing your original laser suggestion.

I'm just thinking that it would probably involve the excitation of iron ions by ram-pressure stripping from (abundant) hydrogen gas protons. No dark matter physics (or even black hole physics) is necessary when one has two galaxies colliding at 3000 km/s (as Ann suggested).
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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by neufer » Tue Jan 02, 2018 7:57 pm

Click to play embedded YouTube video.
BDanielMayfield wrote:
A very reasonable question Ann solution Art. Wouldn't such an ordinary, simple explanation like what Annrt has come up with need to be ruled out before calling up a heretofore unheard of explanation like fluorescent dark matter?
The inflorescence of falling bowl of petunias :?:
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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by BDanielMayfield » Tue Jan 02, 2018 8:11 pm

Were you also making an artful allusion to going out on a limb or over a ledge without much underlying support? That would be a fair comparison to FDM, imho.
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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by ta152h0 » Tue Jan 02, 2018 9:04 pm

Has that evil look, like WR104
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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by neufer » Tue Jan 02, 2018 10:55 pm

BDanielMayfield wrote:
neufer wrote:
Aloe hereroensis, showing
inflorescence with branched peduncle
Were you also making an artful allusion to going out on a limb or over a ledge without much underlying support? That would be a fair comparison to FDM, imho.
  • A-ledgedly.
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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by moontrail » Wed Jan 03, 2018 8:22 am

rstevenson wrote:
moontrail wrote:Maybe the explanation would be more readable in a two columns format. It's difficult for me sometimes to read it in the one column format....
There have been previous suggestions to update the APOD page code, in part for exactly this reason, to make it more readable on a greater variety of screens and for a greater variety of humanoids. But so far, there's been no movement in this direction. I even worked out sample page code a few years ago, to no avail. The keepers of the APOD flame have their reasons, of course, for leaving it as is.

It's possible to use a custom style sheet for individual web sites, if it's worth the bother to you to set one up. I tried it once, but didn't find it all that helpful or easy to use, and the browser add-on that made it happen didn't survive a later system and browser update.

A quick fix that you might find useful: temporarily narrow the page (the entire browser window) as far as required. The text will narrow along with the page, of course.

[edit]
I just downloaded and installed Stylish, a popular add-on for customizing your view of particular sites. It served to remind me why the APOD page needs some rebuilding, even to make it possible to sensibly customize the style for your own viewing needs. The page has effectively no modern structural elements in it, so it's nearly impossible to re-position or style in other ways any of its content elements independently of any other element. For example, it was easy to shrink the description paragraph's width, but it hugged the left page edge. Applying a margin to push it over inexplicably pushed over and shrank the image above it. And so on.

Rob
Thanks for the complete information and suggested methods to skip the difficulty.

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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by Ann » Wed Jan 03, 2018 9:32 am

neufer wrote:
BDanielMayfield wrote:
neufer wrote:
Aloe hereroensis, showing
inflorescence with branched peduncle
Were you also making an artful allusion to going out on a limb or over a ledge without much underlying support? That would be a fair comparison to FDM, imho.
  • A-ledgedly.
Thanks for the free entertainment, Art and Bruce! :D :lol2:

Ann
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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by Chris Peterson » Wed Jan 03, 2018 3:10 pm

neufer wrote:
Chris Peterson wrote:
neufer wrote: Ergo: Ram-pressure stripping of iron atoms by (abundant) hydrogen gas could provide the energy source.
I think the problem is that such a mechanism doesn't explain the nature of the observed spectrum. While there are well understood processes that result in x-ray emission lines, those lines exist against a continuum, and multiple lines are present. It seems like what we have here is a monochromatic source.
I'm not dismissing your original laser suggestion.

I'm just thinking that it would probably involve the excitation of iron ions by ram-pressure stripping from (abundant) hydrogen gas protons. No dark matter physics (or even black hole physics) is necessary when one has two galaxies colliding at 3000 km/s (as Ann suggested).
It wasn't really a suggestion. Just a comment about the first thing I would normally think of when considering a monochromatic source.

It seems like in this case it's easier to say what we aren't looking at then what we are.
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Re: APOD: Unexpected X-Rays from Perseus... (2018 Jan 02)

Post by geckzilla » Wed Jan 03, 2018 4:00 pm

rstevenson wrote:[edit]
I just downloaded and installed Stylish, a popular add-on for customizing your view of particular sites. It served to remind me why the APOD page needs some rebuilding, even to make it possible to sensibly customize the style for your own viewing needs. The page has effectively no modern structural elements in it, so it's nearly impossible to re-position or style in other ways any of its content elements independently of any other element. For example, it was easy to shrink the description paragraph's width, but it hugged the left page edge. Applying a margin to push it over inexplicably pushed over and shrank the image above it. And so on.
Try this. Though there are no class definitions, there are still ways to get around it. I have done more complicated things by using the order of elements themselves to select what I want... although that still broke sometimes because the links at the bottom of the page are sometimes there, and sometimes not. Anyway, this, so far, has not broken. First two lines optional.

Code: Select all

p, h2, h3, center { font-family: sans-serif; }
h1{ font-weight: normal; font-family: serif; }
p { max-width: 800px; margin: 15px auto; line-height: 130%; }
center p:nth-child(3) { max-width: none; }
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