- Astronomers Weigh Heaviest Black Hole Yet
- ‘Cuddle Chemical’ Also Fuels Favoritism, Bigotry
- WikiLeaks Reveals International Intrigue Over Science and Environment
- Songbird’s Sex Hormone Surges at Sight of Flowers
Posted: 12 Jan 2011 08:46 PM PST
SEATTLE — The black hole in the nearby galaxy M87 weighs in at 6.6 billion suns, making it the local universe's heavyweight champ.
"This is the biggest black hole in the nearby universe," said astronomer Karl Gebhardt of the University of Texas at Austin in a press conference today here at the American Astronomical Society meeting.
The behemoth's bulk, plus the fact that it lives just 50 million light-years away, makes M87 the best candidate for future efforts to take a direct image of a black hole's event horizon for the first time.
"In terms of the largest galaxies, it really is in our backyard," Gebhardt said. "Being so close to such a massive black hole allows us a remarkable chance to study what happens around a black hole."
At nearly 6 trillion times the mass of the sun, M87 is the most massive galaxy in the Milky Way's cosmic neighborhood. Astronomers expected it to host a correspondingly huge black hole, but the most commonly accepted estimates — based on measurements from the Hubble Space Telescope — found the black hole weighed just 3 billion solar masses, give or take a billion.
But although Hubble "has taken the lead in terms of black hole measures, it can't do the biggest ones," Gebhardt said.
To pin down the monstrous black hole's mass, Gebhardt and his colleagues used the Gemini North telescope atop Mauna Kea in Hawaii to measure the speeds of stars zipping past the galactic center.
Using a technique called adaptive optics, in which astronomers shine a laser on the sky and use that point of light to subtract out the stars' twinkling, Gebhardt's team was able to measure the velocities of stars within about 2 light-years of M87's center using the Gemini telescope. The scientists also took data with a telescope at the McDonald Observatory in Texas.
The closer stars got to the center of the galaxy, the faster they moved, indicating that a huge hunk of mass lurks at the center to speed stars up. Gebhardt and colleagues used supercomputer models to calculate the black hole's true heft: 6.6 billion suns, give or take 0.25 billion. For comparison, the black hole at the center of the Milky Way is a mere 4 million solar masses.
Most of that mass probably came from gas and stars the black hole has devoured over the millennia. But the trajectories of the stars orbiting the black hole suggest that the solo monster that exists today is the product of two smaller black holes merging into one.
It probably took a few hundred such mergers to build the beast in M87, said Caltech astronomer George Djorgovski, who was not involved in the new work. In the same press conference, Djorgovski announced 16 new black hole pairs that will probably merge in the next few million years.
Big black holes also have big event horizons, the point at which a black hole's gravity is so great even light can't escape. The black hole in M87's event horizon is about 12 billion miles across, three times the size of Pluto's orbit.
"This black hole could swallow our solar system whole," Gebhardt said.
That extensive event horizon would cast a dark shadow on the galactic dust behind it. Future observations with a worldwide network of telescopes looking at wavelengths of light smaller than a millimeter could potentially take a picture of that shadow, proving once and for all that black holes exist.
"We don't know whether black holes are black holes," Gebhardt said. "To actually determine whether an object is a black hole, you need to have some type of proof of the event horizon. That doesn't exist yet. To have an object where we might be able to image it, it's remarkably important."
Image: An artist's rendition of what the black hole's shadow might look like. Credit: Gemini Observatory/AURA illustration by Lynette Cook
Posted: 12 Jan 2011 02:51 PM PST
Men given a dose of oxytocin, a hormone known to promote feelings of love and trust, have revealed the chemical's dark side: It made them more ethnocentric.
When asked to resolve a moral dilemma, such as choosing to save five lives from a runaway train by sacrificing one life, oxytocin-sniffing Dutch men more often saved fellow countrymen over Arabs and Germans than those who didn't get a hormonal whiff.
"Earlier research of oxytocin paints a very rosy view of it. We thought it was odd a neurological system that survived evolution would make people indiscriminately loving toward others," said social psychologist Carsten De Dreu of the University of Amsterdam, co-author of a Jan. 10 study in the Proceedings of the National Academy of Sciences. "Under oxytocin we saw an increase of in-group favoritism, which has the downside of discrimination against people who are not part of your group."
Oxytocin is a hormone made in the brain and some reproductive organs. The body releases the biggest doses of it into the bloodstream during intimate situations (such as caressing), and from there it can dampen fight-or-flight instincts and calm down organs such as the heart.
As a neurotransmitter, it's also intricately involved in social behaviors such as mother-child bonding, feelings of trust and love, and group recognition.
De Dreu's "research flies in the face of how we've thought about oxytocin for decades. It's not all about free love and warm fuzzies," said neuropsychologist Sarina Rodrigues of Oregon State University, who was not involved in the study. "It complements recent data showing oxytocin can promote envy when someone you don't like wins something, or gloating when you win over someone you don't like. It's key to defining where and who we are in society."
To see how oxytocin influenced behavior, De Dreu and his team rounded up several groups of 60 to 70 Dutch men and sat them in front of computers that led them through one of five experiments. All of the experiments were designed to reveal biases toward or against in-groups, such as fellow Dutch, and out-groups, such as Arabs and Germans (people seen as rivals by many Dutch).
In all of the experiments, men who snorted a dose of oxytocin showed stronger and more frequent favoritism towards their countrymen over rival groups. Men who whiffed a placebo still showed signs of favoritism, but less frequently and at weaker levels.
"In a runaway-train scenario, they were more likely to save men with Dutch names than Ahmeds or Helmuts," De Dreu said. The men who sniffed oxytocin were also more likely to sacrifice other nationalities, but not at scientifically significant levels.
De Dreu said the work is a starting point, and that he and his colleague would like to do experiments in more true-to-life settings to see how other conditions affect the oxytocin-induced favoritism and subsequent discrimination.
"We've shown an increase in ethnocentrism under oxytocin, and we tested this in controlled yet artificial conditions," he said. "Oxytocin's effect might be weaker when you're with your friends walking down the street, but it may be stronger. That's something we don't know yet."
Image: Model of oxytocin./NIH
Posted: 12 Jan 2011 02:01 PM PST
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While most of the attention around WikiLeaks' diplomatic cable release involved high-profile geopolitical intrigue, some of the documents involved science and the environment.
Sea Shepherd Whale Deal
The latest of these, reported Jan. 6 by the Guardian newspaper, involve discussions in late 2009 and early 2010 between the United States and Japan over Sea Shepherd, an antiwhaling group that has fought Japan's ongoing hunts on the open seas.
Japan, admitting that Sea Shepherd had effectively limited its kills, asked the United States to investigate the group. The United States agreed and asked Japan to lower its quotas, and to help negotiate lower quotas with Iceland, another whale-killing nation.
The United States eventually asked the International Whaling Commission to pass laws to "guarantee security in the seas," a veiled reference to groups like Sea Shepherd. According to the Guardian, Great Britain and other European countries defeated the proposal.
Image: Sea Shepherd Conservation Society/Flickr.
Posted: 12 Jan 2011 08:00 AM PST
SALT LAKE CITY — As summer heats up, the sight of blooming thistles may give male goldfinches a testosterone kick.
Thistle flowers could signal to American goldfinches that the seeds the songbirds prize for baby food and parent food will soon be abundant, proposes Thomas Luloff of the University of Western Ontario in London, Canada. And in lab setups, male goldfinches housed among blooming Canadian thistles underwent physiological changes that indicate the birds got the "breed now" message from the combination of summery heat and thrilling thistles, Luloff reported January 6 at the annual meeting of the Society for Integrative and Comparative Biology.
What particularly impressed George Bentley of the University of California, Berkeley was that the birds "don't eat the flower — they eat the seeds," he says. Yet the precursor to food still appeared to have an effect.
Biologists still have much to learn about what tips off birds that it's time to breed, says Bentley, who was not part of the research project. Yet, he says, the need to understand those cues is growing as climate change threatens to knock signals out of sync.
Many birds lose what they don't use during the winter, letting hormone concentrations dwindle and reproductive organs shrink. When the breeding season returns, both males and females typically have to recharge and regrow. Much of the earlier work on breeding signals has focused on the broad role of day length or temperature, yet birds can react to other cues too. Species differ in what cues or mixes of cues rev up their breeding biology again.
To see if just looking at thistle flowers would have an effect on goldfinch breeding, Luloff and his colleagues put wild goldfinches, caught during the nonbreeding season, into either of two temperature-controlled rooms. A series of shower curtains allowed birds in both rooms to see either pots of blooming thistles or nonblooming thistles, or no plants at all.
Birds kept in the chill of Canadian spring at 13.5 degrees Celsius during lab daytime didn't experience a testosterone surge in response to thistles. But in the room warmed to a balmy 28 degrees C, birds that could see pots of blooming thistles beside their cage developed twice the testosterone surge found in neighbors screened from blooms with a shower curtain and allowed to see only thistle plants without blooms.
In the warm room, the bloom-viewing males outpaced their bloomless neighbors in testes growth during the early stages of testes expansion. Later, though, the bloomless males caught up.
Bentley raises the question of whether the smell of the thistle blooms inspired the males. Luloff argues that he thinks it's unlikely. Goldfinches don't have much brain area known to be devoted to smelling, and anyway, the shower curtains may have blocked views but let odors circulate.
The idea of a visual food cue isn't completely new, says reproductive biologist Heather E. Watts of Loyola Marymount University in Los Angeles. A 2000 study of antbirds found that the sight of mouthwateringly desirable live crickets affected the male songbirds' physiology and increased their singing.
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