It's commonly admitted that about 80% of the Universe is made of 'dark matter.' But we had only rudimentary ways to detect it, such as high flying balloons. Now, the first satellite designed to detect both antimatter and dark matter has been launched last week. Nature writes that this antimatter observatory, PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics), will catch antiprotons and positrons for the next three years at least. This 470-kilogram satellite is the result of a collaboration between Russia, Italy, Germany and Sweden and the project has only cost about US$32 million. But read more...
Here are some quotes from the Nature article.
The first satellite built to detect antimatter in space launched safely yesterday, boosting the chances of identifying the mysterious 'dark matter' that makes up more than 80% of the stuff in the Universe.
The probe will spend three years in space, and should catch thousands of antiparticles during its mission. "It's the first serious, dedicated space experiment to detect cosmic rays," says Felix Aharonian, an astrophysicist from the Max Planck Institute in Heidelberg, Germany.
"The PAMELA apparatus has an overall height of about 1.2 m and includes a transition radiation detector (TRD) to identify electrons and positrons and a spectrometer based on a permanent magnet equipped with a silicon microstrip tracker to measure particle tracks" as you can see on the image below (Credit: INFN Trieste). Here is a link to a larger version of this illustration.
And below is another recent representation of all the components of the PAMELA probe (Credit: INFN Napoli). Here is a link to a larger version of this diagram.
In "Antimatter and dark matter are new probe's prey," New Scientist gives additional details about this space probe.
"We can recognise the particles' charge, momentum, energy and everything," says team member Piergiorgio Picozza of the University of Rome in Italy. "It is the best detector ever constructed and we will use it for a long period."
PAMELA will be able to detect cosmic rays from ordinary sources, such as supernovae, and possibly exotic sources -- such as stars made of antimatter. Previous cosmic ray detectors sensitive to antimatter have flown on high-altitude balloons or on the US space shuttle, but they have taken data for no more than a week or so.
PAMELA will stay for several years in space and will have plenty of time to find antimatter -- and maybe more...
PAMELA will also search for signs of dark matter, which has been detected only by its gravitational effect on normal matter. Its nature is unknown, but the leading candidate for dark matter is a particle called a neutralino that has a mass of about 100 protons. Neutralinos are thought to annihilate each other to produce proton-antiproton pairs or electron-positron pairs of particular energies.
Let's come back to Nature which tells us why the cost of this project is so low.
Unusually, the big space agencies ESA and NASA have had very little to do with [the project], possibly because PAMELA has always been led by particle physicists rather than space scientists, explains Wolfgang Menn, a physicist at the University of Siegen, Germany, and part of the PAMELA team.
"And we always had good contact with the Russians; it's a lot cheaper to fly on one of their launchers," he adds. The team estimates that the project has cost around 25 million [euros] (US$32 million), at least a tenth of what a similar NASA probe might have cost.
But for the results of this mission, you'll have to wait for several years.
Sources: Mark Peplow, Nature, June 16, 2006; Maggie McKee, New Scientist, June 15, 2006; and various web sites
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