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17 April 2014 12:48 pm ,
Vol. 344 ,
Officials last week revealed that the U.S. contribution to ITER could cost $3.9 billion by 2034—roughly four times the...
An experimental hepatitis B drug that looked safe in animal trials tragically killed five of 15 patients in 1993. Now,...
Using the two high-quality genomes that exist for Neandertals and Denisovans, researchers find clues to gene activity...
A new report from the Intergovernmental Panel on Climate Change (IPCC) concludes that humanity has done little to slow...
Astronomers have discovered an Earth-sized planet in the habitable zone of a red dwarf—a star cooler than the sun—500...
Three years ago, Jennifer Francis of Rutgers University proposed that a warming Arctic was altering the behavior of the...
- 17 April 2014 12:48 pm , Vol. 344 , #6181
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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.