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Big bang reconciled with lithium
In brief– Big bang reconciled If you thought you knew the age of the universe… with lithium
NASA
16 | NewScientist | 12 August 2006
FOR a few years now, astronomers have been quietly confident that the universe is 13.7 billion years old, give or take a hundred million years. They are about to learn that the size and age of the universe are not a done deal. Norbert Przybilla of the University of ErlangenNuremberg, Germany, and his colleagues used the 10-metre Keck-II telescope on Mauna Kea, Hawaii, and other telescopes to measure the distance to a so-called eclipsing binary star system in the Triangulum galaxy,
also known as M33. The team measured light, velocity and temperature to find the true luminosity of the two stars, which eclipse one another on every orbit. Comparing this luminosity with their observed brightness gave a distance to the galaxy of 3.14 million light years – half a million light years further away than anyone thought (www.arxiv. org/astro-ph/0606279). “This is the farthest distance that anyone has been able to measure directly,” says Przybilla. “It’s the cutting edge of what can
be done with these telescopes.” Earlier measurements were based on calculations using the Hubble constant, which is related to the expansion rate of the universe, and hence to its size and age. The smaller the constant, the larger and older the universe. The new result implies that the value of the constant used today is 15 per cent too small, making the universe 15 per cent larger and older. “Our result hints that there may be something interesting happening with the Hubble constant,” says Przybilla. FOODPIX/JUPITER IMAGES
ONE of the niggling things about big bang theory is that it predicts the universe should have far more lithium than we can find. Now we can all rest easy. The stars, it seems, have destroyed the lithium. The lightest elements – hydrogen, helium and lithium – were produced shortly after the big bang. The abundances of hydrogen and helium in the atmospheres of the universe’s oldest stars fit the theory, but there should be two or three times as much lithium. One explanation is that the primordial lithium could have diffused towards the centres of stars and never resurfaced, because fusion reactions destroy the element at only about 2 million °C. In contrast, hydrogen fusion starts at about 10 million °C. “Lithium is a very fragile element,” says Andreas Korn from the University of Uppsala in Sweden. To test the feasibility of this idea, Korn and his colleagues used the Very Large Telescope on Cerro Paranal, Chile, to measure the iron, calcium and titanium content in 18 stars at various evolutionary stages in NGC 6397, a 13.5-billion-year-old star cluster. They used the results to calibrate a model predicting how different elements move around in the stars as they evolve. The model shows that the original lithium content of the stars was twice the average value seen today – in line with the big bang theory (Nature, vol 442, p 657).
Brain growth link to schizophrenia A GENE mutation that alters the shape of the brain in some people with schizophrenia could help explain why the disease often strikes at adolescence. Hugh Gurling of University College London tested people with schizophrenia for mutations in the pericentriolar material 1 (PCM1) gene. Those with mutations had a significantly lower volume of grey matter in their orbitofrontal cortex (Archives of General Psychiatry, vol 63, p 844). “This is the first time anybody has been able to separate out a genetic subtype of schizophrenia and show abnormal brain volume and shape correlated with it,” says Gurling. PCM1 plays a role in cell division, which in the brain occurs more actively at adolescence – an age at which schizophrenia is commonly diagnosed. Abnormal PCM1 activity during this time may disrupt cell division, reducing the orbitofrontal cortex volume. “The sort of symptoms that these schizophrenics get – poor judgement, inappropriate social behaviour and not keeping themselves clean – are linked to this area of the brain,” says Gurling.
Fruity hitchhikers leave you heaving BEWARE the mild-mannered melon. Researchers at the US Centers for Disease Control and Prevention (CDC) have found that since 1973 the cantaloupe melon has been responsible for at least 28 outbreaks of food poisoning in the US and Canada that have left more than 1600 people ill and at least two dead. Of these outbreaks, 68 per cent occurred during the last decade, with Salmonella being the predominant culprit (Epidemiology and Infection, DOI: 10.1017/SO950268805005480). The actual number of cases could be far higher, since one-offs often go
unreported, say the researchers. “Fruit and vegetable produce is now a major source of outbreaks, at the same level as we used to see in meat,” says CDC epidemiologist Christopher Braden at the National Center for Infectious Diseases in Atlanta, Georgia. He blames the rise on increased international trade, which lets people eat melons year-round rather than in local season. It could also be due to more cantaloupes being eaten, he says. The problem with cantaloupes is their rough skin, which can be hard to clean. When they are cut open, bacteria on the skin can contaminate the flesh. The US Food and Drug Administration recommends avoiding blemished melons, and scrubbing the skin under cold water before slicing.
www.newscientist.com
NASA
16 | NewScientist | 12 August 2006
FOR a few years now, astronomers have been quietly confident that the universe is 13.7 billion years old, give or take a hundred million years. They are about to learn that the size and age of the universe are not a done deal. Norbert Przybilla of the University of ErlangenNuremberg, Germany, and his colleagues used the 10-metre Keck-II telescope on Mauna Kea, Hawaii, and other telescopes to measure the distance to a so-called eclipsing binary star system in the Triangulum galaxy,
also known as M33. The team measured light, velocity and temperature to find the true luminosity of the two stars, which eclipse one another on every orbit. Comparing this luminosity with their observed brightness gave a distance to the galaxy of 3.14 million light years – half a million light years further away than anyone thought (www.arxiv. org/astro-ph/0606279). “This is the farthest distance that anyone has been able to measure directly,” says Przybilla. “It’s the cutting edge of what can
be done with these telescopes.” Earlier measurements were based on calculations using the Hubble constant, which is related to the expansion rate of the universe, and hence to its size and age. The smaller the constant, the larger and older the universe. The new result implies that the value of the constant used today is 15 per cent too small, making the universe 15 per cent larger and older. “Our result hints that there may be something interesting happening with the Hubble constant,” says Przybilla. FOODPIX/JUPITER IMAGES
ONE of the niggling things about big bang theory is that it predicts the universe should have far more lithium than we can find. Now we can all rest easy. The stars, it seems, have destroyed the lithium. The lightest elements – hydrogen, helium and lithium – were produced shortly after the big bang. The abundances of hydrogen and helium in the atmospheres of the universe’s oldest stars fit the theory, but there should be two or three times as much lithium. One explanation is that the primordial lithium could have diffused towards the centres of stars and never resurfaced, because fusion reactions destroy the element at only about 2 million °C. In contrast, hydrogen fusion starts at about 10 million °C. “Lithium is a very fragile element,” says Andreas Korn from the University of Uppsala in Sweden. To test the feasibility of this idea, Korn and his colleagues used the Very Large Telescope on Cerro Paranal, Chile, to measure the iron, calcium and titanium content in 18 stars at various evolutionary stages in NGC 6397, a 13.5-billion-year-old star cluster. They used the results to calibrate a model predicting how different elements move around in the stars as they evolve. The model shows that the original lithium content of the stars was twice the average value seen today – in line with the big bang theory (Nature, vol 442, p 657).
Brain growth link to schizophrenia A GENE mutation that alters the shape of the brain in some people with schizophrenia could help explain why the disease often strikes at adolescence. Hugh Gurling of University College London tested people with schizophrenia for mutations in the pericentriolar material 1 (PCM1) gene. Those with mutations had a significantly lower volume of grey matter in their orbitofrontal cortex (Archives of General Psychiatry, vol 63, p 844). “This is the first time anybody has been able to separate out a genetic subtype of schizophrenia and show abnormal brain volume and shape correlated with it,” says Gurling. PCM1 plays a role in cell division, which in the brain occurs more actively at adolescence – an age at which schizophrenia is commonly diagnosed. Abnormal PCM1 activity during this time may disrupt cell division, reducing the orbitofrontal cortex volume. “The sort of symptoms that these schizophrenics get – poor judgement, inappropriate social behaviour and not keeping themselves clean – are linked to this area of the brain,” says Gurling.
Fruity hitchhikers leave you heaving BEWARE the mild-mannered melon. Researchers at the US Centers for Disease Control and Prevention (CDC) have found that since 1973 the cantaloupe melon has been responsible for at least 28 outbreaks of food poisoning in the US and Canada that have left more than 1600 people ill and at least two dead. Of these outbreaks, 68 per cent occurred during the last decade, with Salmonella being the predominant culprit (Epidemiology and Infection, DOI: 10.1017/SO950268805005480). The actual number of cases could be far higher, since one-offs often go
unreported, say the researchers. “Fruit and vegetable produce is now a major source of outbreaks, at the same level as we used to see in meat,” says CDC epidemiologist Christopher Braden at the National Center for Infectious Diseases in Atlanta, Georgia. He blames the rise on increased international trade, which lets people eat melons year-round rather than in local season. It could also be due to more cantaloupes being eaten, he says. The problem with cantaloupes is their rough skin, which can be hard to clean. When they are cut open, bacteria on the skin can contaminate the flesh. The US Food and Drug Administration recommends avoiding blemished melons, and scrubbing the skin under cold water before slicing.
www.newscientist.com