Difference Between Asteroid and Comet

As a kid, we all had this dream of going to space and exploring the unknown. Watching the series on Discovery about space and planets always makes us awestruck. The feeling of being weightless and flying in zero gravity is still something we use to dream in the night. One of the things about space is it is filled with massive objects that are a part of an enormous ballad dancing act. Planets, stars, galaxies all are moving at such a high speed, but none of them are hitting each other. That’s how beautiful space is. From space, we have two things which are not a very common site to humans, the first one is the comet, and then we have asteroids. Both of these are giant rocks that are moving in space with high speed. Still, there are several differences between them, and we are going to discuss these differences between asteroid and comet today in this article. 


What Is Asteroid?

Before we talk about comet vs asteroid, we need to define what does an asteroid means and its proper definition. Asteroids are small and large formations of the rock that orbit the massive bodies in space, such as the sun. They revolve around stars just like planets, but they are quite small in comparison to planets. If you look at our solar system, you will find there are quite a lot of asteroids present in our system. 

Most of the asteroids that we are present in our system resides in the asteroid belt, a region between the orbits of Mars and Jupiter. But don’t think about that’s the only place where you could find an Asteroid, they hang around in other places as well. For example, some asteroids can be seen orbiting the sun on the same path of a planet. Meaning both the planet and the asteroid are following the same way of moving around the sun. Earth is one of the planets that have asteroids like this in its sun’s orbit. 


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(Asteroid on its way to hit the earth, the depiction is fiction based, please don’t consider it to be a real image.)


When talking about asteroids, we need to describe how they formed in the first place. The early signs of our solar system came around 4.6 billion years ago when the big cloud of gas and dust started to collapse inwards. When this was happening, most of the dust particles and dense gases reached the centre of the cloud and formed a star, which we now see as a sun in the day time. 


Other particles that are left behind formed planets in the coming years and those who are left behind were made into small rocks in space, which is called asteroids. 


What Is A Comet? 

In winter, when it is cold you have snow outside, in the same way, space is insanely cold, and thus, some gases come together and form a dusty snowball called comets. These space bodies also orbit around the sun, and they are made up of ice and water for most of the part along with carbon dioxide, ammonia, and methane. 

The centre of the comet is made from ice, and it is covered with a large cloud of gas and dust. It is said that comets are the ones that brought water and other organic compounds that worked as building blocks of life on our earth. 


There’s a special belt of comets in our solar system, which is called the Oort cloud. Comets present in this orbit can take up to 30 million years to complete their single rotation around the sun. Oort cloud has a distance 100,000 times more than the distance between earth and sun.


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(A comet going it way in space, which is close to the earth.)


Every comet has a nucleus in the centre, which is smaller than a few kilometres across the length. As we said it the earlier nucleus of a comet is made from the big icy rocks, frozen gases, and it does have some dust particles also. This sum up all your doubts about what is a comet.


Now, we talk about the tail of the comet, which we make so unique in the night sky. When the comet comes near to earth, it also comes close to the sun. As a result, it starts to develop the atmosphere around itself, as gases and the water begins to melt on the surface. The pressure from the sunlight causes the atmosphere, thus, forming a long bright tail. There are two tails of a single comet, one is the dust tail, and the other one is ion tail, which develops due to gases present inside the comet. These are some of your difference between comet vs asteroid for your better understanding. 

FAQ (Frequently Asked Questions)

1. What are comets made off, which one is the most common comet we can see on earth, and when?

Comets are made of ice, gas, and dust particles, where the centre of the comets is made from ice. Most of the comets that we have in our solar system orbit safely around the sun, meaning they don’t come too close to the sun. On the other hand, we have some comets called sungrazers, that crash straight into the sun if they are big enough or break up and evaporate from the heat as they come close to the sun. Halley’s comet is the most famous comet that we can see from earth. Last time it came close to earth in 1986, the next time it will complete its circle will be 2061, 75 years apart.

2. How big an asteroid needs to be to destroy all the living organisms on earth?

Well, the answer is an asteroid which is just a half a mile long, or smaller than a 1km hits the earth with the speed of 30,000 mph, then no one on earth could survive the impact. Don’t worry, and there are no asteroids in the space that are close to the planet, which is going at such a high speed. So for now, we all safe.