Astrophysics Satellite Detects Dark Matter Clue?
Written by Anne Minard
The PAMELA satellite may have uncovered a new clue indicating dark matter annihilation.
An international collaboration of astronomers is reporting an unusual spike of atmospheric particles that could be a long-sought signature of dark matter.
The orbiting PAMELA satellite, an astrophysics mission operated by Italy, Russia, Germany and Sweden, has detected a glut of positrons — antimatter counterparts to electrons — in the energy range theorized to be associated with the decay of dark matter. The results appear in this week's issue of the journal Nature.
Dark matter is the unseen substance that accounts for most of the mass of our universe, and the presence of which can be inferred from gravitational effects on visible matter. When dark matter particles are annihilated after contact with anti-matter, they should yield a variety of subatomic particles, including electrons and positrons.
Antiparticles account for a small fraction of cosmic rays and are also known to be produced in interactions between cosmic-ray nuclei and atoms in the interstellar medium, which is referred to as a ‘secondary source."
Previous statistically limited measurements of the ratio of positron and electron fluxes have been interpreted as evidence for a primary source for the positrons, as has an increase in the total electron-positron flux at energies between 300 and 600 GeV. Primary sources could include pulsars, microquasars or dark matter annihilation.
Lead study author Oscar Adriani, an astrophysicist at the University of Florence in Italy, and his colleagues are reporting a positron to electron ratio that systematically increases in a way that could indicate dark matter annihilation.
The new paper reports a measurement of the positron fraction in the energy range 1.5–100GeV.
"We find that the positron fraction increases sharply over much of that range, in a way that appears to be completely inconsistent with secondary sources," the authors wrote in the Nature paper. "We therefore conclude that a primary source, be it an astrophysical object or dark matter annihilation, is necessary." Another feasible source for the anitmatter particles, besides dark matter annihilation, could be a pulsar, they note.
PAMELA, which stands for a Payload for Antimatter Matter Exploration and Light Nuclei Astrophysics, was launched in June 2006 and initially slated to last three years. Mission scientists now say it will continue to collect data until at least December 2009, which will help pin down whether the positrons are coming from dark matter anihilation or a single, nearby source.
Source: Nature (there is also an arXiv/astro-ph version here)
Filed under: Dark Matter, Earth Observation, Physics
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April 1st, 2009 at 11:39 am
Unexpected positrons from an unproven form of matter, from an unproven reaction. Unfalsifiable and untestable.
April 1st, 2009 at 11:52 am
Oh thank you Ian, plasma universe forever!!!!
April 1st, 2009 at 12:03 pm
Ian Tresman said
"Unexpected positrons from an unproven form of matter, from an unproven reaction. Unfalsifiable and untestable."
Total rubbish. Positrons are observable in radio active decay. and have been shown experimentally at Caltech by Chung-Yao Chao in 1930. You can observe them today using a positron emission tomography (PET) scanner.
Note: Look like yet another EU crackpot has joined the fray! The Thunderbolts.Info management's current new plan to discredit current accepted theory and investigation. Expect more of this to come.
April 1st, 2009 at 12:03 pm
Ian , please tell the error of our ways.
April 1st, 2009 at 12:09 pm
Ian. I am in Derby this weekend as luck would have it. how about meeting up for a pint ? or do you have to wait for oilis… to ok that sort of thing duck?
April 1st, 2009 at 12:38 pm
Interesting article-however, I stay neutral in these 'exchange of truths' beliefs.
April 1st, 2009 at 1:01 pm
April fool everyone! (at least still is in Finland)
…
..
.
Ok, maybe not.
Unless the bat news wasn't a joke.
Only one question. How come it was detected only now? After 3 years of running is it really possible that it wasn't noticed before? Or did they find it in old data?
April 1st, 2009 at 1:02 pm
Sorry for double-posting, but it actually turned out to be 3 questions. Just to stand corrected before corrected.
April 1st, 2009 at 3:20 pm
"Note: Look like yet another EU crackpot has joined the fray! The Thunderbolts.Info management’s current new plan to discredit current accepted theory and investigation. Expect more of this to come."
They DO all sound the same, don't they?! It'd make an interesting case study in social psychology I reckon.
April 1st, 2009 at 3:29 pm
I can has graviton?
April 1st, 2009 at 3:44 pm
Ian Tresman is correct obviously.
Positrons have no more to do with Dark Matter than they do with invisible pink unicorns.
April 1st, 2009 at 4:04 pm
OilIsMastery said;
"Ian Tresman is correct obviously."
No he is just is a deluded as you, being another crackpot and another Thunderbolts.Info cult member.
Q. What the difference between a EU proponent and a battery?
A. A battery has a positive side!
Note: Look like yet the same EU crackpot has joined the fray with a few of his cult followers! (Peratt's Pimps) Here we see the Thunderbolts.Info management’s current new plan to discredit current accepted theory and investigation. Expect more of this nonsense to come.
April 1st, 2009 at 5:59 pm
Salacius,
You're really loving the influx of EU people aren't you?
April 1st, 2009 at 9:58 pm
I think we should SERIOUSLY consider having these articles just link to a discussion thread on the forums.
April 2nd, 2009 at 12:57 am
Salacious B. Crumb wrote: "Positrons are observable in radio active decay. and have been shown experimentally at Caltech by Chung-Yao Chao in 1930."
No dispute. However, dark matter has never been shown to produce positrons (or have any other kind of particle physics). ie. it is not testable.
This is no different to suggesting that galactic faerie dust emits positrons.
April 2nd, 2009 at 12:59 am
OilIsSlippery wrote: "I am in Derby this weekend". Unfortunately we moved from Derby to Cheshire at the end of Decmeber.
April 2nd, 2009 at 2:37 am
After reading the paper itself (thanks for the link, Anne) these investigators deduced the positron excess as being the result of 1) annihilating DM or 2) a nearby pulsar. How to tell which is the origin of this positron excess? Another group using ATIC to measure the electron spectrum have detected something of a dropoff of energetic electrons and positrons around 600 GeV. The paper: http://arxiv.org/abs/0811.3362 by Jeter Hall and Dan Hooper posits that this dropoff of very high energy electrons and positrons is trying to tell us something about the nature of the excess. They propose using ground-based Atmospheric Cherenkov Telescopes (ACTs) like HESS, MAGIC and VERITAS to tease out the details of their 600 GeV feature in the electron spectrum. A steep dropoff of the spectrum favors Kaluza-Klein DM while a smoother decay in the spectrum indicates a pulsar origin. Their short (4 page) paper includes predicted electron energy spectrum diagrams for each possibility. Although ATIC and PAMELA look at different energy regimes, their observations along with WMAP and ground-based ACTs may be combined to solve this mystery, whatever the outcome.(BOT, Back On Topic)
April 2nd, 2009 at 4:26 am
I love this research. The team have not drawn any firm conclusions as yet, but are speculating and offering alternative causes for the data they have. This is all excellent science work in my opinion.
I hope that the team will be able to draw on more data, and that they will indeed be able to confirm that the positron to electron ratio indicates the existence of DM.
Quite apart from changing out perception of the universe and giving us an indirect method of detecting DM – it might (just might), give the EU nutcases on here something to think about.
April 2nd, 2009 at 6:21 am
An interesting, relevant paper appeared today at the arXiv site that analyzes PAMELA, ATIC & WMAP data to examine this question. The paper: http://arxiv.org/PS_cache/arxiv/pdf/0812/0812.0522v3.pdf looks at three possibilities for these observations 1) annihilating DM, 2) decaying DM and 3) nearby pulsar(s). While having a different take on the 600 GeV feature detected by ATIC, the authors rigorously look at all three scenarios and studied the perspective to discriminate among these models by using synchrotron and IC radiation generated by these positrons-electrons. Seems lots of astronomers and physicists are keenly following these lines of research. BTW, I'm with UKDave on this topic. I love a good science mystery, and this is cutting-edge astrophysics.
April 2nd, 2009 at 7:58 am
Solacious… he never said positrons didn't exist. He stated they were unexpected.
You really do make a lot of mistakes when you aren't copying and pasting information from a paper or article.
Solacious… you say, "radio active". Is this anything like radioactive? Go ahead, lets hear some rediculous reason as to why you spelled it this way…other than the fact you didn't C&P.
BTW, batteries don't have positive 'sides', they have positive 'poles'… since you like to harrass people who don't get everything just perfect.
Yeesh… and your lack of sense. "…a current new plan…??" New plans replace current plans.
You say something like that, and you call someone else a crackpot. Don't forget to label yourself as a bigoted moron.
April 2nd, 2009 at 8:17 am
Supposed "evolution" supporters will try to tell you that humans evolved from chimpanzees over millions of years. Yeah right, try looking at reality for once. Last time I checked chimpanzees don't live any where near even one million years.
April 2nd, 2009 at 8:34 am
InfoMan,
You should read up on what evolutionary biologists actually say about our evolutionary tree. Either you're ignorant or you're trolling.
Or you're OilIsMastery using another name yet again.
April 2nd, 2009 at 9:32 am
From the paper:
"Our high energy data deviate significantly from predictions of
secondary production models, and may constitute the first indirect evidence of dark matter particle annihilations, or the first observation of positron production from near-by pulsars. We also present evidence that solar activity significantly affects the abundance of positrons at low energies."
"Positrons are believed to be mainly created in secondary production processes resulting from the interaction of cosmic-ray nuclei with the interstellar gas."
"Although too statistically limited to draw any significant conclusions, the most recent high energy measurements indicate
a flatter positron fraction than expected from secondary production models."
"Drift effects are at their largest during solar minimum conditions and mostly affect low mass particles such as electrons and positrons, with electrons being favoured in the current solar cycle. A balloon-borne experiment which flew in June 2006 has also observed a low positron fraction at low energies, but with
large statistical uncertainties."
"A rise in the positron fraction at high energy has been postulated for the annihilation of dark matter particles in the galactic halo. The production of positrons through pair production processes in the magnetosphere of near-by pulsars would also yield a similar positron signature. We note, however, that none of the published
models fit our data well and the reason for the rise remains unexplained."
"At low energies (below 5 GeV) the PAMELA results are systematically lower than data collected during the 1990’s and at high energies (above 10 GeV) the PAMELA results show that the positron fraction increases significantly with energy."
I think we all know about the current solar minimum:
"The average pressure of the solar wind has dropped more than 20% since the mid-1990s," says Dave McComas of the Southwest Research Institute in San Antonio, Texas. "This is the weakest it's been since we began monitoring solar wind almost 50 years ago."
There is nothing conclusive in this. The data deviate significantly from predictions. Sensationalist headlines over data that remains "unexplained" by the researchers, yet could very well be explained by the significant decrease in solar wind pressure without invoking "dark matter" to fill the gaps between prediction and observation.
April 2nd, 2009 at 9:53 am
Just as they were going to loose their toy they find something?
April 2nd, 2009 at 12:33 pm
Good discovery, badly titled. They have found more high-energy positrons than expected. The original paper says that it could be explained by dark matter _or_ pulsars. I'm betting on the pulsars. CERN should be able to tell us something about dark matter in the next few years.
April 2nd, 2009 at 8:16 pm
The excess positron flux suggests a decay process for the neutralino, which is a mixed state of the supersymmetric partner for the Higgs, photon and neutrino. The energy range for this dark matter particle, or neutralino is within the experimental reach of the LHC.
Lawrence B. Crowell