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19 December 2013 12:36 pm ,
Vol. 342 ,
After 20 years of trying, researchers have finally convicted massive volcanic eruptions in Siberia as the culprit in...
Five federally funded optical and radio telescopes in the United States could be forced to shut down over the next 3...
A 2-year budget agreement pushes back the threat of sequestration but leaves scientists still wondering how much money...
After a decade away from physics, Robert Laughlin, a Nobel laureate at Stanford University in Palo Alto, California,...
Computer scientists and others have teamed up to persuade the 117 state parties to the Convention on Certain...
The swine flu pandemic of late 2009 had a peculiar aftereffect in parts of Europe: a spike in children being diagnosed...
- 19 December 2013 12:36 pm , Vol. 342 , #6165
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ScienceShot: Stars of Heavy Metal
1 August 2013 1:15 am
The most lead-rich stars known to science may represent a brief stage in stellar evolution that scientists have theorized but previously haven’t seen. The small suns, known as HE 2359-2844 (artist’s representation shown) in the constellation Sculptor and HE 1256-2738 in Hydra, were among nine identified as being helium-rich in a previous survey of stars. But new analyses show that these two are doubly unusual because they also sport atmospheres with lead concentrations about 10,000 times those seen in the atmosphere of our sun, the researchers report online today in Monthly Notices of the Royal Astronomical Society. The surface temperatures of these two bluish stars are estimated to be about 38,000°C (far hotter than our sun’s surface temperature of about 5500°C), so hot that lead atoms in their atmospheres have been stripped of three electrons. The stars may be passing through a stage of stellar evolution that lasts no more than a few tens of thousands of years, the scientists say—a phase between red giants (about 30 or 40 times the size of our sun) and blue subdwarfs (stars about one-fifth the size of our sun but seven times hotter and 70 times brighter). The lead surrounding the stars—which was part of the original cloud of gas and dust from which these stars formed, not generated by reactions in the evolving stars themselves—may be dispersed within an atmospheric layer as much as 100 kilometers thick (depicted patchily in pink) that altogether weighs up to 100 billion metric tons.