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incorrectly because the organic coating alters their optical (light absorbing or reflecting) and physical-chemical (aerosol-cloud interac- tion) properties. At the time, the Las Conchas fire was the largest in New Mexico history (156,000 acres); however, the following year the Whitewater-Baldy Complex fire became the new record holder (289,000 acres), and Dubey’s team confirmed their dark tarball and coated- soot findings from that fire as well. Emissions from burning biomass include both light-absorbing particles (soot and black carbon) as climate warmers and light-scattering particles (organic carbon and smoke) as climate coolers. Current climate models typically indicate small wildfire contributions to climate because they assume that the warming par- ticles and cooling particles offset each other’s effect. Dubey’s work has shown that not only is the composition of carbon-based aerosols more complex than previously realized, but the rela- tive warming and cooling contributions of each of these types of particles do not necessarily cancel: warming can win. Dubey concludes that global climate models, which only include organic aerosols (cooling) and bare soot (warming), ought to include both kinds of tarballs (warming and cooling) as well as soot coated with organics (more warming than bare soot). Punctuating this recom- mendation is the rising incidence of record- breaking wildfires in New Mexico, the American Southwest, and the rest of the world. It is a ferocious feedback loop: as the climate warms from greenhouse gas emissions, fires will be larger, hotter, and more frequent and will emit an abundance of tarballs and soot. The next challenge is to determine just how much warm- ing is actually canceled by cooling. According to Dubey, it may be less than we thought. —Eleanor Hutterer a windfall. Cas A is a supernova remnant— the stellar debris that remains after the core of a supermassive star implodes and gives birth to a neutron star, but then explodes and blows the rest of the star apart. NuSTAR is NASA’s high-energy x-ray telescope that had been mapping the location of titanium nuclei in the still-expanding debris field, now some 10 light- years across. The windfall, however, begins with NuStar’s older brother spacecraft, the Chandra X-ray Observatory. “The Cas A debris field is turbulent,” says Fryer, “and over the course of several years, Chandra captured beautiful images of turbulent mixing. We hoped we could use the images to test our computer codes, but that wasn’t possible at the time.” Every computer simulation of a supernova includes code that accounts for turbulence in the core and body of the star. But is that code correct, and are the physics models that describe the turbulence correct or even adequate? The only way to be sure is to simulate the system and compare its output turbulence with the signature swirls, whorls, and plumes displayed by the real system. However, the swirls and whorls seen in Cas A today are in part due the shape of the star’s core when it blew up. That shape was unknown, and thus there was too much uncertainty in the simulation to deduce if it reflected reality or not. Interestingly, turbulence also shows up in another system that first implodes then explodes—the plutonium core of a nuclear weapon. Like the astrophysicists, weapons scientists need to validate and verify their com- puter codes that model weapons performance. Unfortunately, it is extraordinarily difficult to obtain data that could be used to test the weapons code. Fryer had proposed using the Cas A data. Wait a minute. Why should the turbulence within a supernova remnant 10 light-years across have anything to do with the turbulence of a detonated nuclear device? The answer is that the underlying physics is the same—and the physics governs the type of turbulence that emerges within each system. “We’ve been able to learn more about how to model a nuclear weapon by modeling supernovae,” says Fryer. Supernovae are perhaps the best examples of how basic science, the cornerstone of the U.S. and the world’s technological powerhouses, can support the weapons program. But it’s not the only example. In many specialized areas of science, where the expertise has traditionally resided behind the security fence, the much larger peloton of academic and private-sector scientists has closed the gap in basic knowl- edge, and as Fryer sees it, has a lot to offer the secretive and traditionally self-contained world of nuclear weapons. Fryer has ties to both the academic and weapons communities. As a member of NuSTAR’s science team, he’s privy to the telescope’s data. The titanium nuclei that were being mapped are only created in the core of a massive star and thus serve as markers for core material. What caught his eye was that the nuclei were distributed in a way that was entirely consistent with the latest models of core collapse and explosion. That meant that astrophysicists had a handle on the shape of the core that created Cas A and could estimate the uncertainties in reproducing the turbulence observed by Chandra. And that weapons scien- tists could to do similar tests with their codes using the Chandra data—for free. —Jay Schecker Supernova for National Security What Los Alamos astrophysicist Chris Fryer realized as he looked at the latest NuSTAR images of Cassiopeia A (Cas A) was that, in a curious way, the country had just been handed A composite image of the supernova remnant Cassiopeia A, combining low-energy (red), medium-energy (green), and high-energy (blue) x-ray images taken by the Chandra X-ray Observatory. The tiny bright dot in the center is believed to harbor a neutron star. CREDIT: NASA/CXC/SAO 29