APOD: Space Station Detector Finds Excess... (2014 Oct 06)

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APOD: Space Station Detector Finds Excess... (2014 Oct 06)

Postby APOD Robot » Mon Oct 06, 2014 4:08 am

Image Space Station Detector Finds Unexplained Positron Excess

Explanation: Where did all these high energy positrons come from? The Alpha Magnetic Spectrometer (AMS-02) onboard the International Space Station (ISS) has been meticulously recording how often it is struck by both high energy electrons and positrons since 2011. After accumulating years of data, it has now become clear that there are significantly more positrons than expected at the highest energies detected. The excess may have a very exciting and profound origin -- the annihilation of distant but previously undetected dark matter particles. However, it is also possible that astronomical sources such as pulsars are creating the unexplained discrepancy. The topic remains a very active area of research. Pictured here, the AMS is visible on the ISS just after being installed, with a US Space Shuttle docked on the far right, a Russian Soyuz capsule docked on the far left, and the blue Earth that houses all nations visible across the background.

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Re: APOD: Space Station Detector Finds Excess... (2014 Oct 0

Postby Cousin Ricky » Mon Oct 06, 2014 1:11 pm

We're surrounded by anti-matter? I was wondering where Star Trek would find enough of the stuff to power their warp drives. :mrgreen:

Pyrhan

Re: APOD: Space Station Detector Finds Excess... (2014 Oct 0

Postby Pyrhan » Mon Oct 06, 2014 1:41 pm

Er... this might be a detail, but the filename of the picture says "amsiss_sts134_4288.jpg"

However, the STS 134 mission was flown by the space shuttle Endeavour, whereas the shuttle in this picture is Atlantis. Therefore, the picture could only have been taken during STS 135, the only mission flown by Atlantis after AMS 02 was installed (and last mission flown by any space shuttle).

So, perhaps you should correct the picture's filename, just to avoid any confusion.
Thanks.

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Re: APOD: Space Station Detector Finds Excess... (2014 Oct 0

Postby Chris Peterson » Mon Oct 06, 2014 1:58 pm

Cousin Ricky wrote:We're surrounded by anti-matter? I was wondering where Star Trek would find enough of the stuff to power their warp drives.

Yeah. In the same way that when you go swimming in the ocean, you're surrounded by gold (except that the gold is orders of magnitude more abundant than antimatter).
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Re: APOD: Space Station Detector Finds Excess... (2014 Oct 0

Postby Boomer12k » Mon Oct 06, 2014 2:00 pm

Interesting prospects either way....Personally I think Pulsars....just because they are a more known quantity...but I could be wrong...science....will have to Win Out on that.

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Re: APOD: Space Station Detector Finds Excess... (2014 Oct 0

Postby Chris Peterson » Mon Oct 06, 2014 2:18 pm

Pyrhan wrote:Er... this might be a detail, but the filename of the picture says "amsiss_sts134_4288.jpg"

However, the STS 134 mission was flown by the space shuttle Endeavour, whereas the shuttle in this picture is Atlantis. Therefore, the picture could only have been taken during STS 135, the only mission flown by Atlantis after AMS 02 was installed (and last mission flown by any space shuttle).

So, perhaps you should correct the picture's filename, just to avoid any confusion.
Thanks.

The astronaut who took the image was not associated with either STS-134 or STS-135. He flew up on a Soyuz and was part of Expedition 28. The instrument flew up on STS-134, even though the STS-135 shuttle was present at the time this particular image was made.

It looks like the original image may have been named "iss028e016131", but in general I don't think it's a good idea to worry too much about the image name. What's important is that all of the descriptive information is accurate.
Chris

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Re: APOD: Space Station Detector Finds Excess... (2014 Oct 0

Postby Ralph » Mon Oct 06, 2014 2:51 pm

Chris Peterson wrote:What's important is that all of the descriptive information is accurate.


Which is a shame as it says
APOD Robot wrote: After accumulating years of data, it has now become clear that there are significantly more positrons than electrons at the highest energies detected


which is incorrect, there is more antimatter than we expect, but the fraction of antimatter is still peaking at about 0.15 http://journals.aps.org/prl/abstract/10 ... 113.121101

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Re: APOD: Space Station Detector Finds Excess... (2014 Oct 0

Postby Chris Peterson » Mon Oct 06, 2014 3:36 pm

Ralph wrote:
Chris Peterson wrote:What's important is that all of the descriptive information is accurate.


Which is a shame as it says
APOD Robot wrote: After accumulating years of data, it has now become clear that there are significantly more positrons than electrons at the highest energies detected


which is incorrect, there is more antimatter than we expect, but the fraction of antimatter is still peaking at about 0.15 http://journals.aps.org/prl/abstract/10 ... 113.121101

Of course, I was referring only to the mission information in that context.

I agree, the summary of the scientific conclusion appears incorrect in the APOD.

flux.gif
The unexpected results being reported on are related to the different spectral indexes of the electrons and positrons as a function of energy, and of the different behavior in the flux of each above about 10 GeV. It does appear that the actual flux of positrons in the measured range never exceeds about 20% of the electron flux. So there aren't more positrons than electrons at any energy level. As you say, just more than expected.
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Re: APOD: Space Station Detector Finds Excess... (2014 Oct 0

Postby geckzilla » Mon Oct 06, 2014 3:41 pm

I emailed the editors with a link to your posts Ralph and Chris.
Just call me "geck" because "zilla" is like a last name.

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Re: APOD: Space Station Detector Finds Excess... (2014 Oct 0

Postby RJN » Mon Oct 06, 2014 4:04 pm

Yes, the the positron flux, although unexpectedly high, does not exceed the electron flux. I was thrown off by Figure 3 in their PRL paper found here: http://ams.nasa.gov/Documents/AMS_Publications/PhysRevLett.113.121102.pdf , wrongly thinking that spectral index was directly indicative of flux. Thanks for calling this to my attention. I apologize for the oversight, and have now fixed the text. - RJN

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Re: APOD: Space Station Detector Finds Excess... (2014 Oct 0

Postby ta152h0 » Mon Oct 06, 2014 8:33 pm

I am sure the Big Poobah in the Sky has a few more surprizes for the mere mortals , denizens of this earth.
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Re: APOD: Space Station Detector Finds Excess... (2014 Oct 0

Postby JohnD » Mon Oct 06, 2014 9:14 pm

What's that on the right that looks like a carefully packed box of kid's toys?
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Re: APOD: Space Station Detector Finds Excess... (2014 Oct 0

Postby geckzilla » Mon Oct 06, 2014 9:56 pm

JohnD wrote:What's that on the right that looks like a carefully packed box of kid's toys?
JOhn

I saw those too. I would guess that is a container full of space exposure experiments.
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