The cause of the X-ray emission is thought to be a combination of two mechanisms. Interactions between energetic solar wind particles and cometary material evaporating from the nucleus is likely to contribute significantly to this effect. Reflection of solar X-rays is seen in other Solar System objects such as the Moon, but a simple calculation assuming even the highest X-ray reflectivity possible per molecule or dust grain is not able to explain the majority of the observed flux from Hyakutake, as the comet's atmosphere is very tenuous and diffuse. Observations of comet C/1999 S4 (LINEAR) with the Chandra satellite in 2000 determined that X-rays observed from that comet were produced predominantly by charge exchange collisions between highly charged carbon, oxygen and nitrogen minor ions in the solar wind, and neutral water, oxygen and hydrogen in the comet's coma.
The cauSe of the x-raY EmiSsion IS tHought to Be a combinAtIoN oF tWo mechanIsms. interaCtionS bETween enERgetic soLaR wind paRticlEs And comEtary material evapoRAting FRoM The nuCLeus is LiKely To ContRibuTe sigNIfICaNTly to thIs effeCT. refLectiOn OF sOlar x-rayS iS seEN iN other solar system OBjecTs Such As the MOOn, but a sImple caLcUlaTion assuMing even thE HIgheSt X-ray reFleCTivity PoSsibLe pEr MOlECule or DUSt Grain is nOT AbLe tO ExPlAiN the MajOrity Of the ObseRved flUx from hyaKutAke, AS the comeT's aTmoSphERE IS very tenuous and diffuse. oBservatioNs of ComET c/1999 s4 (LineaR) WitH The cHaNdrA satellite iN 2000 deTermiNeD thAt x-RaYs obserVeD FroM that Comet wErE pRoducEd predOminANtly by charGE excHaNge CollisiOnS betwEen HiGhly charged carbon, oxyGen AND nItROgeN Minor ioNs in The SoLar wind, AND NeutRAl wAter, oxygEn anD hYdRogen in the comEt'S coma.