Why do comets have tails?

Generally, comets got kicked out from their home which are the Oort Cloud and the Kuiper Belt. This phenomena occur due to the pull of the gravity by planets or stars. Then, their journey of growing tails begin by moving toward the inner solar system.

Far from the Sun, small comets look the same as small asteroids, completely frozen and this dirty snowball is in solid form. As it approaches the Sun, it starts to heat up and ices begin to vaporize into gas that easily escapes the comet’s weak gravity. A combination of solar radiation pressure and the solar wind (stream of charged particles from the Sun)  sweep the vaporize materials and dust back forming two separate tails :

  1. Ion tail 
  2. Dust tail
Distinction between ion and dust tail by Comet Tail

An ion tail forms when UV from the Sun rips electrons from gas atoms in the coma (cometary), making them into ions through ionization. Then, the solar wind carries these ions  away from the Sun resulting straighter and narrower tail.

On the other hand, a dust tail contains small particles (size similar with cigarette smoke). The reason this tail forms due to the presence of the solar radiation pressure that pushes on these particles, shoving them away from the nucleus of the comets. Due to the relatively weak pressure from the sunlight , the dust particles end up forming a diffuse and curved tail that typically appears white or pink relative from the Earth


 comet GIF
Comet Swan by GIPHY

Apparently, based on recent observations, comets are not the only objects in our solar system that grow tails. These observations stated that asteroids can also sprout dust tails on occasion.


6 thoughts on “Why do comets have tails?

  1. Hi, I’ve never really thought about why Comets have tails! At first thought it seems to be intuitive until I realized that there is no friction in space, meaning nothing should be tailing behind. Thank you for explaining this phenomenon! I have to wonder though, to the gasses that escape the comet change its course at all? Or is it negligible?


    1. I think it totally depends on the space time curvature of our solar system and one more crucial point if the gasses are accelerating, it might have normal and tangential acceleration, so the course might change according the component of the acceleration.


  2. This is a super interesting subject to write about and I’m glad I know more about it now! It’s crazy to think that the sun has a “solar wind” of particles shooting out of it. really puts in perspective how much energy the sun really has.


    1. Yaaaa… I won’t either know this fact until I made some research on the internet. Sun has a lot of impact on our solar system hence we need to study more about our beloved star.


  3. OH MY. I’ve never known this before. I saw this in class just now and I can totally relate it to your post. Nice explanations! Hm, I wonder, what other celestial bodies that have tails too?


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