Gravity remains the dominant force on large astronomical scales, but when it comes to stars in young star clusters the dynamics in these crowded environments cannot be simply explained by the pull of gravity.
Hubble Space Telescope image of the young star cluster NGC 1818 in the Large Magellanic Cloud. KIAA researchers found to their surprise an increasing fraction of binary systems as they looked at increasingly larger distances from the cluster center, as illustrated graphically in the inset. Image: Peking University
After analyzing Hubble Space Telescope images of star cluster NGC 1818 in the Large Magellanic Cloud, a satellite galaxy of the Milky Way, researchers at the Kavli Institute for Astronomy and Astrophysics (KIAA) at Peking University in Beijing found more binary star systems toward the periphery of cluster than in the center – the opposite of what they expected. The surprising distribution of binaries is thought to result from complex interactions among stars within young clusters.
In the dynamic environment of a star cluster, high-mass stars are thought to gravitate toward the center of a cluster when they give a ‘kick’ to lower-mass stars and lose energy, explained KIAA Prof. Richard de Grijs, who led the study. This leads them to sink to the cluster center, while the lower-mass stars gain energy and might move to orbits at greater distances from the cluster core. Astronomers call this process “mass segregation.”
However, when the Kavli researchers looked closely at binary star systems within NGC 1818, they found a much more complex picture.
Most stars in clusters actually form in pairs, called “binary stars,” which initially are located so close to one another that they interact, resulting in the destruction of some binary systems. Other binaries, meanwhile, swap partners. Astronomers had expected that the same process that leads a cluster’s most massive stars to gravitate toward the center would also apply to binaries. This is because together, the stars that make up binaries have more mass on average than a single star.
When the astronomers discovered that there were more binaries the farther from the core they observed, they were initially baffled by this unexpected result. They concluded that so-called “soft” binary systems, in which the two stars orbit each other at rather large distances, are destroyed due to close encounters with other stars near the cluster’s center. Meanwhile, “hard” binaries, in which the two stars orbit one another at much shorter distances, survive close encounters with other stars much better, all throughout a cluster. This is why more binaries were seen farther out than close in.
Mapping the radial distribution of binary systems in dense star clusters had never been done before for clusters as young as NGC 1818, which is thought to be 15-30 million years old. This is difficult to do in any case, because there are no young clusters nearby in our own Milky Way galaxy. The new result provides new insights into theoretically predicted processes that govern the evolution of star clusters.
“The extremely dynamic interactions among stars in clusters complicates our understanding of gravity,” team member Chengyuan Li said. “One needs to investigate the entire physical environment to fully understand what’s happening in that environment. Things are usually more complex than they appear.”
Breast cancer patients with high levels of vitamin D in their blood are twice as likely to survive the disease as women with low levels of this nutrient, report UC San Diego School of Medicine researchers in the March issue of Anticancer Research.
In previous studies, Cedric Garland, professor in the Department of Family and Preventive Medicine, showed that low vitamin D levels were linked to a high risk of premenopausal breast cancer. That finding, he says, prompted him to question the relationship between 25-hydroxyvitamin D — a metabolite produced by the body from the ingestion of vitamin D — and breast cancer survival rates.
A study, published today in Nature’s Scientific Reports, identifies a new technology that could see flexible electronics, such as roll-up tablet computers, widely available in the near future. So far, this area of electronic design has been hampered by unreliability and complexity of production.
Researchers from the Univ. of Surrey worked together with scientists from Philips to further develop the Source-Gated-Transistor (SGT) — a simple circuit component invented jointly by the teams. Previously, they found that the component could be applied to many electronic designs of an analog nature, and display screens. Through this current study, researchers have now shown that SGTs can also be applied to next-generation digital circuits.
Millions of high school and college algebra students are united in a shared agony over solving for x and y, and for those to whom the answers don’t come easily, it gets worse: most preschoolers and kindergarteners can do some algebra before even entering a math class.
In a just-published study in the journal Developmental Science, lead author and post-doctoral fellow Melissa Kibbe and Lisa Feigenson, associate professor of psychological and brain sciences at Johns Hopkins Univ.’s Krieger School of Arts and Sciences, find that most preschoolers and kindergarteners, or children between four and six, can do basic algebra naturally.
Federal forecasters predict a warming of the central Pacific Ocean this year that will change weather worldwide. And that’s good news for a weather-weary U.S.
The warming, called an El Nino, is expected to lead to fewer Atlantic hurricanes and more rain next winter for drought-stricken California and southern states, and even a milder winter for the nation’s frigid northern tier next year, meteorologists say.
Paleontologists studying fossilized feathers have proposed that the shapes of certain microscopic structures inside the feathers can tell us the color of ancient birds. But, new research from North Carolina State Univ. demonstrates that it is not yet possible to tell if these structures – thought to be melanosomes – are what they seem, or if they are merely the remnants of ancient bacteria.
Melanosomes are small, pigment-filled sacs located inside the cells of feathers and other pigmented tissues of vertebrates. They contain melanin, which can give feathers colors ranging from brownish-red to gray to solid black. Melanosomes are either oblong or round in shape, and the identification of these small bodies in preserved feathers has led to speculation about the physiology, habitats, coloration and lifestyles of the extinct animals, including dinosaurs, that once possessed them.