Description: 当彗星靠近太阳时，太阳辐射会加热彗星表面。表面的冰变成气体（"升华"），同时带走岩石和尘埃物质。由此产生的混合物在彗核周围形成一团云，这就是彗发。一般来说，彗星会有两条尾巴：喷射出的尘埃粒子形成彗尾，彗尾呈典型的弯曲状。它由从表面释放出来的尘埃粒子组成，这些尘埃粒子沿着彗星的轨道绕太阳运行。尘埃尾的长度可达数百万公里或更长。它们反射太阳光，如果条件合适，肉眼能观测到的彗星大部分都是由它们的白色漫射形状组成的。

相当一部分气体被太阳风--太阳发出的带电粒子--吹走并电离。这些离子形成了彗星的离子尾，通常呈蓝色。离子尾总是直指太阳。如果彗星本身正在远离太阳，离子尾就会在彗星之前。

Related Terms:

• 彗发
• 彗星
• 彗核

Term and definition status: The original definition of this term in English have been approved by a research astronomer and a teacher
The translation of this term and its definition is still awaiting approval

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