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More dark chatter February 9, 2009

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While Mars and exoplanets stole most of the science headlines in 2008, papers reporting results from a number of cosmic ray detectors gathered a lot of attention in the (astro-)physics community. Excesses in the number of particles detected at high energies (~50 GeV) that could not be explained by theoretical predictions sparked speculations that cosmic ray satellite PAMELA may be picking up the signature of dark matter in the Galaxy. A commonly accepted scenario for the nature of dark matter are the so-called WIMPs, or weakly interacting massive particles, which don’t interact in “regular” processes but may annihilate each other to produce high energy cosmic radiation. A number of cosmic ray and gamma ray detectors have produced intriguing results, leaving scientists with an intricate puzzle of information to assemble into a coherent picture.

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An Early Universe 101 December 23, 2008

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I’ve been learning a bit recently about dark matter, dark energy and the history of the Universe, which are all fascinating. Mark over on Cosmic Variance has writted this interesting post on preheating in the early Universe. This proposed phenomenon has important consequences for the formation theory of dark matter, amongst other things.

While I’m on the topic, one of the best books I read this year was The Inflationary Universe by Alan Guth. I admit I don’t read as many popular science books as I should, and I finish even fewer – but this one is a cracker. Guth builds an excellent story about how he arrived at the theory, in collaboration and in conflict with other scientists around the world. It’s a fascinating account of a great scientific discovery, told in such an anecdotal style that it’s super easy to read. It’s completely rekindled my interest in fundamental physics and cosmology, which explains some recent posts (here, or here) on the topic 🙂

‘Arrested development’ at work in the Universe December 17, 2008

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Left: Composite image of galaxy cluster Abell 85, using X-ray data (purple) from Chandra and optical image from the Sloan Digistal Sky Survey. Right: Snapshots of the Universe's evolution from a simulation by Volker Springel of MPA, at 0.9, 3.2 and 13.7 billion years.

A cross-continental team of astronomers led by Andrei Vikhlinin have used data from the American X-ray space telescope Chandra to help pin down the nature of the most enigmatic stuff in the Universe, dark energy. By observing clusters of galaxies over a range of different ages, the team were able to track how their masses have evolved over the history of the Universe. Using the statistics of this evolution and comparing them with results from several other complimentary studies, they have significantly narrowed the constraints on the precise nature of dark energy.

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The cosmic ray signature of dark matter? November 24, 2008

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Detecting supersymmtric dark matter

Detecting supersymmtric dark matter

A very interesting paper was published in last week’s issue of Nature – I blogged about it before after reading the NASA press release. It’s wasn’t all that helpful without reading the actual paper but the cosmic ray – dark matetr link caught my attention.

Just today a conference paper (i.e. not peer-reviewed) appeared on astro-ph about some preliminary results from PAMELA – another cosmic ray detector that focuses on antiparticles (positrons and antiprotons). Recall that PAMELA was the source of some controversy earlier this year. Another paper on PAMELA data was posted on astro-ph back in October, it’s listed as being submitted to Nature so again, not reviewed yet. But perhaps another cosmic rays Nature paper soon, and there’s certainly a lot of buzz!

I had a read through these papers and some background stuff – it’s something I didn’t know much about and it’s very cool. Cosmic rays: inneresting akshually!

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A Cosmic Challenge October 30, 2008

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Galaxies Magnified by Galaxy Cluster Abell 1689's "Gravitational Lens"

Galaxies Magnified by Galaxy Cluster Abell 1689

Cosmology, the study of the Universe on the very largest of scales, is a frustrating business. The vast majority of the matter in the Universe is unaccounted for, and of a large fraction, which we call Dark Energy, we have no idea what it even might look like, let alone how to find it. One important source of information comes from the study of gravitational lenses. When light from the most distant sources travels across the Universe, it is distorted by intervening matter, as predicted by Einstein’s general theory of relativity. By studying the distortions seen in these distant objects, cosmologists gather information about the properties of the large-scale matter distribution along the line of sight.

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