Friday, March 20, 2015

Nova sweeping clean

Over 13 years the blast from GK Persei shows an oddity or two. And "As the shock wave expanded and heated an increasing amount of matter, the temperature behind the wave of energy should have decreased. The observed fading and constant temperature suggests that the wave of energy has swept up a negligible amount of gas in the environment around the star over the past 13 years. This suggests that the wave must currently be expanding into a region of much lower density than before, giving clues to stellar neighborhood in which GK Persei resides."

Maybe that's not so surprising. The current model for novas is that one of a binary star pair becomes a neutron star, and slowly accumulates matter from its companion until enough collects to spark a humongous nuclear explosion. I don't know how long this process would take--that would depend on how close the companion was, among other things. If the cycle is only a few million years, we'd not see the repetition rate (yet), but the blasts would come frequently enough to sweep out a lot of local gas. I think. If the pair is "swimming upstream" in the local galactic gas fresh stuff would blow in pretty quickly. "Quickly" being a relative term...

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