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Researchers ‘look inside’ antimatter
EUROPEAN scientists have carried out the first experiments on antimatter.
Researchers in Geneva, Switzerland, have been able to trap and control anti-hydrogen atoms in a chamber at a sufficiently low temperature to begin studying their physics in detail.
They say the development should help them get a better understanding of how antimatter differs from normal matter and why the latter has come to dominate the Universe around us.
According to mainstream thinking, equal amounts of matter and anti-matter should have been created in the Big Bang at the beginning of time — and then annihilated each other in a flash of energy.
Quite why one form won out over the other has yet to be explained.
Large quantities: Anti-matter is like a mirror image of normal matter in that their constituent parts have apparently opposite properties.
In the simplest normal element, hydrogen, a negatively charged electron orbits a proton nucleus; but in an anti-hydrogen atom, a positively charged particle — a positron — orbits an anti-proton nucleus.
Researchers at the European Nuclear Physics Research Centre (Cern) recently announced they had the ability to make anti-atoms of hydrogen in substantial quantities. Now they say they can store these fragile objects for study as well, allowing them to conduct simple experiments.
Mike Charlton, who works at Cern, told the media: “This work is important because it will enable us to understand why there is any matter at all in the Universe. This is one of the great mysteries.
“This work gives us a whole new avenue to explore that didn’t exist a few weeks ago.”
The Cern researchers created the antimatter by accelerating particles to near the speed of light and then crashing them on to a plate.
One in a million of the resulting fragments is suitable for making anti-atoms. Anti-protons are collected and stored in a cloud of low-energy positrons, which act like a fridge, cooling the particles down until they combine into anti-atoms.
Research team member Walter Oelert said: “In 1996 we produced only a few atoms of anti-hydrogen at a velocity close to the speed of light, which is equivalent to a temperature 100,000 times that of the inner part of the Sun.
“You can imagine that this material is too hot to handle. Now, we have anti-hydrogen in much larger quantities as cold as only a few degrees above absolute zero.”
In their first experiments on anti-hydrogen, the research team broke up their newly created atoms using an electric field.
By measuring the strength of the electric field, they hope to tell how tightly an anti-atom is held together and shed light on the differences between normal matter and antimatter that might explain why the Universe exists in its present form.
Cern physicist Jerry Gabrielse said: “Our long-term goal is to try to look very precisely at this anti-atom, and by comparing the world’s simplest antimatter atom and the world’s simplest matter atom to make a very fundamental test of basic physics theories.”
The research is being published in the journal Physical Review Letters.
‘Oldest’ star found
This is the oldest star in our Milky Way yet observed by astronomers. It could date back to the beginning of the Universe, about 14 billion years ago.
The giant star, HE0107-5240, is a rarity because unlike younger stars it is virtually metal-free. It is from the first generation of stars made from the simple elements left over from the Big Bang.
Writing in the journal Nature researchers say, “these old stars provide crucial clues to the star formation history and the synthesis of chemical elements in the early Universe.
They add: “If totally metal-free stars could be found, this would allow the direct study of the pristine gas from the Big Bang.”
After the Big Bang, the Universe consisted of mostly hydrogen, some helium and a little lithium, so the first stars to form would have contained only these elements.
It was the first generation of stars that converted these lighter elements into heavier ones like carbon, phosphorous, iron and lead — collectively known to astronomers as metals.
When those stars exploded they “polluted” the cosmos with these heavier elements, which themselves went into a later generation of stars — like our Sun.
The existence of stars with zero or very low metal content has been predicted for decades, but none has ever been found, leading some to suspect they never existed — until the discovery of HE0107-5240.
The star was spotted in the outer reaches of our galaxy by Norbert Christlieb, at the University of Hamburg in Germany, and colleagues.
It lies in the direction of the southern constellation Phoenix, at a distance of about 36,000 light-years. The star has just 1/200,000th of the metal content of our Sun.
It was initially discovered at the Siding Spring Observatory in Australia. High precision follow-on observations were made at the European Southern Observatory in Chile, using one of the huge, new units of the Very Large Telescope (VLT).
The discovery of HE0107-5240 fills an important gap in theories about how elements form in star, but it also raises some questions.
Why have no stars been found between 1/10,000 and 1/200,000 of the Sun’s metal abundance?
“Only time, and the extension of new surveys to even fainter stars will tell,” says Catherine Pilachowski, an astronomer at Indiana University in Bloomington, USA. — Dawn Sciencedotcom Report
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