关于彗星的几个问题

1.彗星其实很小

彗星分为彗核、彗发和彗尾三部分,一般我们看到的都是彗尾。

其实,彗星的核心部分是彗核,它并不大,直径可能只有几公里,这就是它们的核心部分,由岩石和冰组成。彗星在接近太阳的时候,才会发生“爆发”,甩出长长的彗尾。

2.彗星其实也很大

虽说彗星的彗核很小,但只要甩出长长的彗尾,那它的范围就非常大了。一条彗尾拖出去几十万公里,那是常有的事。2007年当霍姆斯彗星开始远离太阳的时候,它的彗尾甚至长达几千万公里。而太阳的直径,也只有139万公里而已。

这也不是最长的,最长的彗尾可以达到2亿公里。如果彗核在太阳处,彗尾甚至可以触及火星。

3.彗星更像小行星

其实,彗星的尾巴不是经常有的。在远离太阳的区域,彗星没有尾巴,只有彗核。而彗核的形状,和小行星比较相似。

彗星的轨道一般都很扁,近日点距离太阳非常近,而远日点甚至在海王星轨道以外。因此,绝大部分时间内,彗星都没有彗尾,只有一个彗核。

4.彗星可以有不止一个彗尾

在我们的印象里,彗星都是拖着一个长长的尾巴在空中飞行。

其实,在一些特殊的情况下,彗星可以有不止一个彗尾。比如天文学上比较著名的海尔-波普彗星,就有不止一个彗尾。

首先,彗核的气体在接近太阳的过程中被蒸发,然后在太阳风的作用下被“吹”到身后,形成了一条彗尾。

同时,这些气体被电离的离子和电子在太阳磁场的作用下重新结合,就会发出光来,形成一条新的彗尾。比如海尔-波普彗星的彗尾,就是由一氧化碳形成的蓝色彗尾。

据天文学家描述,这还不是最牛的,官方记录中最牛的彗星,有6条彗尾。

5.彗星每次靠近太阳都更接近死亡

既然我们说,彗星的彗尾是由它的彗核产生的,这也就意味着,每次靠近太阳的时候,就会损失很多的物质。

因此,每当彗星回到近日点的时候,也是它折寿的一趟旅程。终有一天,就会因此而全部蒸发掉。

6.彗星会带来流星雨

彗星损失的部分,有的时候就会进入大气层,坠入地球,就会形成流星雨。比如我们常说的英仙座流星雨、狮子座流星雨、双子座流星雨,都是由彗星产生的。

在20世纪90年代,狮子座流星雨就迎来了巨大的爆发,当时,流星雨最多的时候每小时有上千颗,是观测流星雨的绝佳机会。

7.彗星比小行星更危险

像我们刚才说的,彗星的轨道过于狭长,导致它们在远离太阳的时候难以观测,运行规律也没有小行星那么稳定,难以捉摸。

而且,彗星在从海王星轨道甚至更远的地方飞向太阳,会经历数十亿甚至上百亿公里的持续加速,速度非常非常快。万一它们撞上地球,威力会非常大。

好在,彗星撞击地球这种事,发生的概率非常低。据推测,上一次彗星撞地球,还是6500万年前。

《关于彗星的几个问题》有0个想法

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