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5 December 2013 11:26 am ,
Vol. 342 ,
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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ScienceShot: Reconstructing Galactic History
31 July 2013 1:00 pm
How did our galaxy form and evolve? To find out, astronomers try to ascertain the ages of the Milky Way's oldest components. Especially useful are globular clusters, old, tight-packed stellar gatherings that serve as time capsules preserving conditions from the Milky Way's youth. Now, as astronomers report online today in Nature, Hubble observations of white dwarf stars have nailed down the age of the great globular cluster 47 Tucanae (shown). Located 15,000 light-years from Earth, this cluster is the second brightest globular in the sky, after Omega Centauri. The new data reveal that 47 Tucanae is 9.9 billion years old, plus or minus 700 million years. For a globular, the cluster is metal-rich—its iron-to-hydrogen ratio is a fifth of the sun's—and is 2 billion years younger than a metal-poor globular dated with the same technique. Metal-poor and metal-rich globulars belong to two different components of the Milky Way, so these ages help reconstruct galactic history. Metal-poor globulars are part of the ancient stellar halo surrounding the Milky Way's disk, while metal-rich globulars reside in the galaxy's bulge and thick disk; therefore, the difference in age means that billions of years elapsed from the formation of the stellar halo to the birth of the thick disk.