w 10 | ive from the Labs cnrsI InternatIonal magazIne L Astronomy New Cosmic Rays Identified BY tomrIdgway q the region of the arches cluster seen w and in the nearin X-rays (contours) A century ago, physicist Victor Franz Hess discoveredthathigh-speedparticles—atomicnu- infrared (background cleiorelectrons—werereachingtheEarthfromthe image) was MilkyWay.These“cosmicrays,”astheywerelater identified as a source called,arebelievedtobesuperchargedwithkinetic cosmic rays.of low-energy energy by the shockwaves of supernovae explo- sions,whichallowsthemtopassthroughsolarwinds P andpenetratetheinnerSolarSystem.Cosmicrays withlowerenergylevels—lessthanhalfabillion electron-volts—have proved harder to find and study as they never reach our System. Now, energy cosmic rays (LECRs) of galactic origin,2 ESA-XMM/NASA-HST/thelow-fromhadronicfirstcolleaguesthehisanddiscoveredTatischeffhave1VincentCSNSMenabling researchers to start looking into their chemical composition, flux, and effects on © theinsterstellarmedium. isparticularlyimportantsinceitprovesthatparticles Orsay TofindasourceofLECRs,Tatischeffandhisteam can be charged with kinetic energy not only by neededtobuildatheoreticalmodelofwhatLECR- supernovae explosions but also by the simple createdX-rayemissionsintheinterstellarmedium movementofstars. wouldlooklike,andcompareitwiththedatagath- “Newobservationsatradioandinfraredwave- eredbyXMM-Newtonsinceitslaunchin1999.They lengthscouldenableustostudythiscolossalfluxof thusidentifiedasourceofLECRsinthevicinityofthe LECRsanditsphysicochemicaleffectsonthedense Archesclusterofyoungstars,about100lightyears gas in the interstellar medium,” says Tatischeff. fromthecenteroftheMilkyWay.“Theparticlesthere “ThisshouldproveinterestinginlightoftheseLECRs’ areacceleratedinthebowshockcreatedbythe possibleinfluenceonstarformation.” cluster’sownmotion,thusgeneratingacharacteris- ticX-rayemissionbyirradiatingtheambientgas 01.(CNRS/universitéParis-Sud). etdespectrométriedemasse csnsm,orsay. Ion:nformatIontactcnucléairespectrométriedeCentre cloud, which we were able to identify using our 02. Tatischeffetal.,“NonthermalX-raysfromlow-energycosmicrays: > vincent.tatischeff@csnsm.in2p3.frVincent TatischeffclusterArchesthefromemissionlinekeV6.4thetoApplication model,”saysTatischeff.ThediscoveryoftheseLECRs region,”A&A,2012.546:A88. TeeTh Fossils KeyTo DieTaryevoluTion BY fuI leeluk w lifelong habitat and dietary changes of found in surrounding bedrock.the Eating habits say a lot about people. they can even reveal biological and social individuals.remarkably, the technique scientists deduced that the hominins traits of our extinct ancestors, as also keeps the teeth relatively intact: the shared the same home range area, close geochemists from thelgl1 and biologists tiny holes made by the beams are to the caves where their bones were from theamIs2 lab have shown.3 By invisible to the eye. excavated.to detect their dietary studying teeth fossils fromsouthafrica’s three hominin genera were content, the team measured the cradle ofhumankind site, the team has examined:Australopithecus africanus enamel’s barium and strontium reconstructed the diets of hominins, (2 to3 million years old),Paranthropus concentrations, known to decrease as a unlocking details on the early humans. robustus (1.2 to2.5 million years old), and mammal goes up the food chain and Lyon Vincent Balter of thelgl likens earlyHomo (Homo sapiens’ precursor starts eating meat. “teeth to trees that produce rings as dating back2.3 to2.4 million years ago). so what did our forbears chew on? they grow, telling a person’s history.” using strontium isotope analysis, the Australopithecus had the most varied using an innovative laser ablation team tracked a specimen’s habitat by diet, scrounging anything from animal technique exposing growth prisms on matching levels of water and plant remains to plant matter.the later two dental enamel, the team traced the strontium absorbed in enamel, to those groups derived from this common
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