Light from nearby blue stars - more energetic than the bright star Antares - knocks electrons away from the gas, which then shines when the electrons recombine with the gas.

• 附近蓝色恒星（能量比亮星心宿二高）发出的蓝光剥夺了周尾气体中的电子，而后当气体又重新得到电子后发光。