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On the night of November 14, at the Palomar Observatory outside San Diego, Yale astrophysicist David Rabinowitz '83 and his colleagues programmed the Schmidt wide-field telescope to scour a swath of sky. Every hour and a half, a powerful digital camera developed at Yale recorded an image; during the night, a computer analyzed the pictures.
When the scientists examined the data, they found something surprising: one of the “stars” had moved. The team, Rabinowitz says, had located “the largest new object found in the solar system since the discovery of Pluto in 1930.”
After rechecking their results, Rabinowitz, Mike Brown of Caltech, and Chad Trujillo of the Gemini Observatory in Hawaii announced on March 15 their discovery of a reddish ball of rock and ice, just a bit smaller than Pluto, whose vast orbit greatly expands the size of our solar system. Pluto averages about 4 billion miles from the sun; the new object is currently 8 billion miles from the sun, and its elongated 10,500-year orbit will eventually take it 84 billion miles distant. “The solar system doesn’t end with Neptune and Pluto,” says Rabinowitz. “It goes out at least 30 times farther than we'd thought.” The three astronomers named the object Sedna, after the Inuit goddess of the ocean.
In February, the team garnered headlines with the discovery of 2004 DW, an object slightly smaller than Sedna. In 2002, they found Quaoar, similar to 2004 DW in size and in having an orbit that roughly follows Pluto's. Because of their small size, all three objects are classified as planetoids, or “plutinos,” rather than planets. (Pluto itself would not be considered a planet if it were discovered today.)
The key to this work is Yale’s new QUEST Large Area Camera. The instrument, built under the direction of Charles Baltay, the Eugene Higgins Professor of Physics and Astronomy, weighs 200 pounds and has a 176-megapixel photo capacity (a typical consumer camera can manage only 3 megapixels). It can image large patches of sky with great precision, and the astronomers are using it at Mt. Palomar to undertake the first complete planet survey of the heavens in nearly 75 years.
Scientists believe that the distant objects found by Rabinowitz and company are made of material unaltered since the beginning of the solar system and may therefore hold clues to the origin of the planets. They also believe there are more plutinos out there. “Some of the most significant members of our solar system remain to be discovered,” says Rabinowitz.
Virgins and STDs
Three years ago, assistant professor of sociology Hannah Brueckner published data showing that the virginity pledge works—at least for a while. Teens who pledge to stay virgins until they marry start having intercourse an average of 18 months later than other teens. But Brueckner’s newest research suggests that teens who have taken the pledge may be subject to substantial risks from sexually transmitted diseases (STDs) once they start having sex.
Brueckner and coauthor Peter Bearman of Columbia showed that, as young adults, the would-be virgins are less likely than other young adults to protect themselves from infection. In their analysis of data from the National Longitudinal Study of Adolescent Health, the researchers examined the self-reported behavior of 12,000 teenagers, beginning in 1994, and found that while virginity pledgers have sex later and with fewer partners, they tend to be less aware than their peers of the possible hazards of sexual activity. (However, when Brueckner and Bearman looked at the results of urine tests—which offer a more objective measure of STD prevalence than self-reports—they found that the incidence of infection is equally high in pledgers and non-pledgers.)
Brueckner speculates that teens who promise to abstain may not know how to prepare adequately for sex. “Many abstinence-only curricula create an everything-or-nothing mind-set,” she says. “There’s no acknowledgement that there are ways to have safe sex.”
How can sex educators encourage informed sexual attitudes, without condoning early experimentation? Brueckner says the best approach is an all-inclusive one, focusing on both the benefits of abstinence and the viability of other options. “The virginity pledge can be a useful tool, because it gives kids a mechanism to say no if they don’t feel like having sex,” she says. “But studies are showing a consensus that comprehensive sex education is best. The more you talk openly about sex, the more likely kids are to use condoms and contraception.”
Doctor of decay
Last September, Fauja Singh finished the Toronto marathon in about five hours and forty minutes. That’s long for top marathoners—the fastest times are closing in on two hours—but it was a world record for Singh’s age group. He is, after all, 92.
Ray Fair was delighted. “The time is very close to what I predicted,” says Fair, the John M. Musser Professor of Economics. His work normally involves forecasting economic trends, but for the past ten years he has also been using his mathematical tools to predict something else: the decline of aging but in-shape athletes.
In a draft of a paper posted in February on his web site, http://fairmodel.econ.yale.edu/aging, Fair analyzes data of U.S.-record performances, organized by age, in several sports. He notes that from age 35 until about 70, the decline within a particular category is fairly steady (0.89 percent per year for running, 1.12 percent for swimming, and 1.55 percent for field events). After a “transition point” at 70 or so, the decline starts to accelerate, jumping by an additional 0.20 percent every year. The rates apply to athletes both male and female, world-class and not.
“What’s encouraging is how small the slowdown is,” says Fair, who is 61 and a veteran of 18 marathons. “If you stay in good shape, the rate of deterioration is less than you'd think. It takes roughly until your mid-80s for times to double.”
Fair bases his analyses on the “least squares” method developed in the nineteenth century by Karl Friedrich Gauss, in part to predict the orbits of asteroids, and refined it. In a recent book, Predicting Presidential Elections and Other Things, he applies his methods to wine quality, interest rates, college grades, and even the likelihood of people having extramarital affairs. (“An extra ten years of marriage . increases the number of sexual encounters per year by between five and six.” But the effect is offset by other factors, such as age.)
“The game is to find a line that best fits the data,” explains Fair. In the case of sports, the “line” represents the theoretical best performance. On his web site, Fair provides a calculator that allows runners, track and field athletes, and swimmers to determine what their age-corrected best efforts should be. “The goal is to stay on your regression line,” he says.
But it’s not that easy—and Fair would know. By his own estimate, he should have finished last November’s Philadelphia marathon in 3:24:05. He came in 20 minutes late. So he’s training harder, and looking forward to October.
Atkins and risk
New findings by Yale epidemiologist Tongzhang Zheng might give pause to Atkins Diet devotees: for women, a diet high in fat or protein—Atkins staples—significantly increases the chances of developing non-Hodgkin’s lymphoma. A high-fiber diet reduces the risk.
“If you have a higher intake of fat, particularly saturated fat, your risk almost doubles,” says Zheng, who studied the diets of and disease incidence among 1,300 Connecticut women from 1995 to 2001. “For the most prevalent and deadly non-Hodgkin’s lymphoma, your risk almost triples.” High protein consumption also resulted in increased risk, while eating fruits and vegetables cut the risk by 40 to 60 percent, Zheng wrote in a paper published in the American Journal of Epidemiology.
Zheng himself steers clear of the debate about the benefits and drawbacks of the Atkins plan. “My suggestion is a balanced diet,” he says. But Zheng has personal experience with its popularity. Visiting family in central China, he found two of his three sisters following Atkins.
Under the influence
“Party membership, “ says social psychologist Geoffrey L. Cohen, “can bend the way you see the world.”
We like to think of our political beliefs as bedrock principles. But in research published last winter in the Journal of Personality and Social Psychology, Cohen showed how powerfully group influence can sway them. He conducted several experiments with undergraduate subjects from Yale, Stanford, and the University of Washington—151 liberal Democrats and 62 conservative Republicans in all. Cohen began by asking each student to evaluate two very different versions of a state welfare proposal. Predictably, the liberal students favored the more generous policy, the conservatives the more stringent one.
But when Cohen told liberal students that Democrats were pushing for a harsh policy, something bizarre happened: the liberals adopted the new party line. Conversely, conservative students who were told that Republicans had loosened the purse-strings suddenly found a generous stance on welfare acceptable. Both liberals and conservatives even wrote thoughtful essays espousing positions they had opposed until their respective political parties supposedly embraced them.
Nor were the students aware of this belief-bending effect. “They denied being influenced themselves,” says Cohen, “but they believed their political adversaries and even their allies were under the sway of their party.”
Because Cohen examined the phenomenon in only one age group and has not explored it among political independents, he is not ready to declare that it applies to everyone. Still, the existence of a pervasive, if largely invisible, shaping of political beliefs makes sense. “Humans are a very social species, and we may have evolved to be responsive to the needs of our group,” says Cohen, who suggests a bit of humility may be in order whenever we assert our objectivity. “A person’s sense of identity is tied to the group, and when there’s cognitive dissonance between reality and the group, people tend to go with the group more than they think.”
When a senior citizen living independently becomes disabled, what are the odds for a return to self-sufficiency? Better than the experts thought, says Susan E. Hardy, a geriatrics researcher at the Medical School. In the April 7 Journal of the American Medical Association, Hardy and Yale geriatrician Thomas M. Gill report that in a group of New Haven seniors, 81 percent were back on their feet within a year, and more than half of those remained independent for six months or longer.
Neurobiologist Tamas L. Horvath offers new evidence that the adult brain is not a fixed entity. In the April 2 Science, Horvath and his colleagues report on their study of transgenic mice that can’t produce leptin, a hunger-blocking hormone. The defect leads to obesity in the animals, but giving the rodents leptin led to a “rapid rewiring” of the appetite control center of the brain. Since it also resulted in a decrease in overeating, dieters hope the finding applies to humans.
Epidemiologist Michael B. Bracken and his colleagues argue that much animal research on clinical treatments “is wasted because it is poorly conducted.” In the February 28 British Medical Journal, the Bracken group called for more rigor in the design of the experiments and for systematic reviews to “improve the precision of estimated treatment effects.”
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