螺旋波等离子体是一种高密度的低温低气压等离子体。
Helicon plasma is a kind of high density, low temperature plasma in low pressure.
在螺旋波里，轨道则是逐渐弯曲，所以密度变大的区域是曲线状。
In a spiral wave, the orbits are progressively misaligned, so that the region of enhanced density is a curved line.
另一种说法是，壳状结构如同是池塘中的波纹，是NGC 474与位在其上的螺旋星系正在进行的碰撞所产生的密度波搅动而激起的。
Alternatively the shells may be like ripples in a pond, where the ongoing collision with the spiral galaxy just above NGC 474 is causing density waves to ripple though the galactic giant.
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