Milky Way's massive black hole shot its wad 300 years ago
Astronomers have long wondered why the mega–black hole at the center of the Milky Way, weighing as much as four million suns, shines billions of times less brightly than similarly hefty black holes in other galaxies. A new study to appear in Publications of the Astronomical Society of Japan attempts to solve the mystery by probing x-ray flare-ups in a large gas cloud near the black hole, known as Sagittarius A* (pronounced "A-star"). The flare-ups represent an echo of the black hole's activity, because they are triggered by x-rays it emits that take 300 years to travel the intervening distance. Combining data from Japan's Suzaku and ASCA (Advanced Satellite for Cosmology and Astrophyics) x-ray satellites, along with NASA's and the European Space Agency's Chandra and XMM–Newton x-ray observatories, respectively, researchers deduced from the flares that Sagittarius A* shined a million times more brightly three centuries ago than it does today. They speculate that the black hole pooped itself out—and is now resting.
New ion engine gives satellite cruise control
When the European Space Agency launches the Gravity field and Steady State Ocean Circulation Explorer (GOCE) later this summer, it will carry a new type of engine that expels a stream of ions to produce a thrust equivalent to the weight of a postcard, the BBC reports. The T5, designed by QinetiQ, a Hampshire, England–based defense and security technology company, took decades and tens of millions of dollars to develop. Similar ion engines, which extract electricity from solar radiation to accelerate charged particles, have been used before in Smart 1, a European probe that orbited the moon, and NASA's Deep Space 1 spacecraft. The T5 will act as cruise control for GOCE as it maps variations in Earth's gravity from orbit, where winds will buffet it to and fro.
Are we fast enough to mind our brains?
Ten seconds is an eternity when someone has but an instant to make up his or her mind. But a team of German researchers reports in Nature Neuroscience that decisions are actually made in the brain up to 10 seconds before people become conscious of arriving at and acting on them. Study subjects were asked to decide whether to push a button with their left or right hands while their brains were scanned by functional magnetic resonance imaging. The scientists from the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, Germany, say they accurately predicted their choices based on activity in the frontopolar and parietal cortices, brain regions known to be involved with sophisticated decision making. The researchers believe that the frontopolar cortex makes a choice and the parietal cortex notes the result and shuttles it to the conscious mind. Study co-author John-Dylan Haynes, a neuroscientist, says that the new work makes a case against free will. "The question is," he says, "can we still decide against the decision our brain has made?" (The Boston Globe)
Day traders' mid-day testosterone level predicts their successes and flops
It seems that testosterone may be the driver behind buying on margin and tapping inside information when it comes to gaming the market. Cambridge University researchers swabbed the mouths of 17 male traders at a London-based financial institution at 11 in the morning and again at four in the afternoon to measure their levels of the stress hormone cortisol as well as of the male hormone testosterone, which is known to jump when men win and dip when they lose. To their surprise, testosterone not only rose in traders who had better than average days, but the morning levels predicted how they would do. The research team, reporting in Proceedings of the National Academy of Sciences USA, also determined that levels of cortisol (which is secreted by the adrenal glands) spiked, as expected, when traders made particularly high-risk moves. (The Economist)