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Flash Physics: US energy agency needs more time, Sun’s runaway twin, chemical analysis of fingerprints

14 Jun 2017 Sarah Tesh

Flash Physics is our daily pick of the latest need-to-know developments from the global physics community selected by Physics World‘s team of editors and reporters

Hot topic: ARPA-E has funded projects that will directly harness the Sun's energy

Threatened US energy agency needs time to deliver

The Advanced Research Projects Agency-Energy (ARPA-E) has the ability to make significant contributions to energy research but must be allowed time to do so, according to a report by the US National Academies of Sciences, Engineering and Medicine. The academies’ report – An Assessment of ARPA-E – says that the agency is making progress towards its goals but cannot be expected to have fulfilled them yet, given that new energy technologies require decades of effort. Operated by the US Department of Energy, ARPA-E was created in 2009 to fund high-risk, high-reward research. The report finds that a quarter of supported projects have received follow-on funding, while around a half have published their results in peer-reviewed journals, with 13% receiving patents. The 18 strong committee that wrote the report recommends that ARPA-E management now develop a way of measuring and assessing the agency’s impact to demonstrate the agency’s value. The report comes just weeks after US president Donald Trump included no money for the agency in his administration’s 2018 budget request.

New evidence says the Sun had a runaway twin

The Sun likely had a non-identical twin that escaped into the depths of the Milky Way a long time ago. This is according to Sarah Sadavoy of the Harvard-Smithsonian Center for Astrophysics in the US and Steven Stahler from the University of California, Berkley, who have theorized that all Sun-like stars are born in pairs. The idea that the Sun once had a twin is not new. The long-lost sibling is called Nemesis and may have kicked out the asteroid that exterminated the dinosaurs. However, astronomers have struggled to find the evidence to support the existence of Nemesis. Now, Sadavoy and Stahler have run a series of statistical models to try and find one that fits the populations of single and binary young stars seen within the Perseus giant molecular cloud during a radio survey. “The only model that could reproduce the data was one in which all stars form initially as wide binaries,” says Stahler, where “wide” refers to a separation of at least 500 AU apart – 17 times the distance between the Sun and Neptune. “These systems then either shrink or break apart within a million years.” In Sadavoy and Stahler’s model, stars with masses similar to the Sun start as wide binaries within star-forming egg-shaped cores. “As the egg contracts, the densest part will be toward the middle, and that forms two concentrations of density along the middle axis,” Stahler explains. “These centres of higher density at some point collapse in on themselves because of their self-gravity to form stars.” 60% of the time, the stars then separate, but for the remaining 40%, the pairs go on to form tight binaries. The work is presented in the Monthly Notices of the Royal Astronomical Society.

Laser lift-off boosts chemical analysis of fingerprints

A new way to analyse the chemical composition of fingerprints has been developed by researchers at Louisiana State University in the US. The system uses an infrared laser to vaporize material that is left behind when a person touches a surface. While this might sound like a violent process, the laser wavelength was carefully selected to heat up water molecules while minimizing damage to biological molecules such as DNA. Material is removed from a region about 0.3 mm in diameter – leaving most of the fingerprint intact – and the vapour is sucked into a filter that captures the molecules of interest. The contents of the filter can then be analysed using a number of different techniques, including mass spectrometry. The system was developed by Fabrizio Donnarumma, Eden Camp and colleagues, who say that it could also be used to work out if a person had been handling explosive materials. Indeed, the technique was able to identify a range of substances including caffeine, antiseptic cream and TNT using mass spectrometry. The team is now working with industry and police agencies to come up with ways to use the portable system to analyse chemical signatures left at crime scenes. The research is described in the Journal of the American Society for Mass Spectrometry.

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