Center for Combustion Energy and Department of Thermal Engineering, Tsinghua University, Beijing 100084, China.
Phys Rev Lett. 2011 Oct 21;107(17):171102. doi: 10.1103/PhysRevLett.107.171102. Epub 2011 Oct 18.
The accelerative expansion of the Crab Nebula's outer envelope is a mystery in dynamics, as a conventional expanding blast wave decelerates when bumping into the surrounding interstellar medium. Here we show that the strong relativistic pulsar wind bumping into its surrounding nebula induces energy-generating processes and initiates a detonation wave that propagates outward to form the current outer edge, namely, the shock front, of the nebula. The resulting detonation wave, with a reactive downstream, then provides the needed power to maintain propagation of the shock front. Furthermore, relaxation of the curvature-induced reduction of the propagation velocity from the initial state of formation to the asymptotic, planar state of Chapman-Jouguet propagation explains the observed accelerative expansion. Potential richness in incorporating reactive fronts in the description of various astronomical phenomena is expected.
蟹状星云外壳的加速膨胀在动力学上是一个谜，因为常规的膨胀激波在与周围星际介质碰撞时会减速。在这里，我们表明，强烈的相对论性脉冲星风与周围的星云碰撞会引发能量产生过程，并引发爆震波向外传播，从而形成星云当前的外边缘，即激波前沿。由此产生的爆震波及其下游的反应，然后提供维持激波前沿传播所需的动力。此外，曲率引起的传播速度从初始形成状态到Chapman-Jouguet 传播的渐近平面状态的减小的弛豫，解释了观测到的加速膨胀。预计在描述各种天文现象时，反应前沿的丰富性将会得到体现。
