Sun 'stops chickenpox spreading'

Sun 'stops chickenpox spreading'

"The University of London team found chickenpox less common in regions with high UV levels, reports the journal Virology.  Sunlight may inactivate viruses on the skin, making it harder to pass on. However, other experts say that other factors, including temperature, humidity, and even living conditions are equally likely to play a role.  

The varicella-zoster virus is highly contagious, while it can be spread through the coughs and sneezes in the early stages of the infection, the main source is contact with the trademark rash of blisters and spots.

UV light has long been known to inactivate viruses, and Dr Phil Rice, from St George's, University of London, who led the research, believes that this holds the key why chickenpox is less common and less easily passed from person to person in tropical countries.

It could also help explain why chickenpox is more common in the colder seasons in temperate countries such as the UK - as people have less exposure to sunlight, he said.

He examined data from 25 earlier studies on varicella-zoster virus in a variety of countries around the world, and plotted these data against a range of climatic factors.

This showed an obvious link between UV levels and chickenpox virus prevalence.

Even initially confusing results could be explained - the peak incidence of chickenpox in India and Sri Lanka is during the hottest, driest and sunniest season.

However, Dr Rice found that, due to atmospheric pollution, UV rays were actually much lower during this season compared with the rainier seasons.

He said: "No-one had considered UV as a factor before, but when I looked at the epidemiological studies they showed a good correlation between global latitude and the presence of the virus."

Professor Judy Breuer from University College London said that while UV could well be contributing to the differences in the prevalence of chickenpox between tropical and temperate regions, there were other factors which needed to be considered.

She said: "Lots of things aside from UV could affect it - heat, humidity and social factors such as overcrowding.

"It's quite possible that UV is having an effect, but we don't have any firm evidence showing the extent this is happening." (...)"

in BBC

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Scientists Find a Black Hole the Size of 21 Billion Suns

Scientists Find a Black Hole the Size of 21 Billion Suns

"They're huge. They're voracious. They're blacker than a panther on a moonless night. They're black holes, the mind-bending, space-warping cosmic objects with gravity so insanely powerful that even a beam of light that wanders too close will be sucked in, never to emerge. Einstein's theory of general relativity predicted they might exist, but the great physicist himself doubted it would really happen.

Einstein was wrong. Over the past decade or two, black holes have been discovered all over the place — small ones peppered around the Milky Way and huge ones, impressively called "supermassive" black holes, lurking the centers of galaxies. The one at the core of Milky Way weighs as much as a couple of million stars, and it could swallow the sun without even noticing, the way you'd swallow a pistachio.

But that's positively puny compared with the two new black holes, each about 330 million light-years away or so, just announced in the journal Nature. The smaller one, located inside a galaxy known as NGC 3842, is as massive as 9.7 billion suns, and the other, in a galaxy called NGC 4889, is more than twice as large: if you put it on a very large balance, it would take at least 21 billion stars to even things out. Another way to think about things: even the smaller of the two is nearly 30% bigger than the previous record holder, announced last winter, and it would make for a great storyline if astronomers were surprised, amazed, flabbergasted, blown away by the awesome giganticness of these monsters. Truthfully, though, they kind of expected it. "If we infer the existence of quasar black holes of ten billion solar masses at early cosmic times," Harvard theorist Avi Loeb told Nature's Ron Cowen for the journal's online news blog, "we'd better find their counterparts in the present-day Universe."

Loeb is referring to quasars — beacons of light so intensely bright they can be seen halfway across the universe. When astronomers first spotted them in the late 1950s, nobody knew what they were. Nowadays, everyone pretty much agrees that quasars are supermassive black holes at the cores of young galaxies. The holes themselves aren't visible, of course, but when they suck in surrounding matter, the stuff heats up to millions of degrees, sending bursts of energy shooting across the cosmos.

Back when the universe was young, there was plenty of gas floating around to feed these monsters. Nowadays, much of it the gas is gone, and so are the quasars — but the black holes that powered them should, as Loeb says, still be around (where would they go, after all?). Now, thanks to some of the world's most powerful telescopes, astronomers know that indeed they are. While scientists can't see the black holes directly, they can see stars whipping around at high speeds in the two galaxies' cores — and by clocking those speeds carefully, the astronomers can calculate how big and how dense the object they're orbiting must be. In each of these cases, nothing but a supermassive black hole fits the bill.

Such observations are technically difficult, so in one sense the latest black-hole discoveries are extraordinary. Still, astronomers expected to find such things all along, so it might not seem like such a big deal to space experts. Indeed, Martin Rees, the British astronomer royal, dubbed the new results "an incremental step" in the New York Times, with nary a word about shock or awe. If you've got a professional interest in how black holes were born and how they evolved, this is more grist for the mill.

For the rest of us — well, they're just kind of awesome."

in Time

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