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What Are Comets? What Are They Made Of?

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Night scene with a comet

If you think that the ice sitting behind your local ice-skating rink is gross, wait until you learn about comets. Comets are large, dirty cosmic snowballs that orbit around the Sun. These snowballs are made up of rock, dust, and ice, hence the nickname “dirty cosmic snowball.” 

To learn more about what comets are and what they are made out of, keep reading.

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What Are Comets?

NASA defines comets¹ as the frozen leftovers of the Solar System’s formation. As the leftovers, comets are made up of a conglomeration of ice, rock, dust, and debris. Although we do not know for certain where these comets come from, scientists have pretty good guesses.

It is believed that comets orbit our Sun from the Kuiper Belt or the distant Oort Cloud. Although there are only 3,743 known comets, scientists believe that there might be billions of comets out there.

Regardless of how many comets there are, all of them do one thing: they orbit the Sun. As the comet gets closer to the Sun, its speed increases, which causes its head to heat up and spew dust everywhere. As a result, the tail of the comet is formed.

Comet Neowise as seen in Canada
Image Credit: Jim Cumming, Shutterstock

What Are Comets Mainly Made Out Of?

Scientists have been able to test what comets are made out of by studying the comets that have come into our Solar System and planet. Scientists can also determine what materials comets consist of by studying the reflection of the comet. A few space missions have even been able to collect comet samples for further clarification.

Studies¹ have found that comets are made up primarily of ice, various gases, dust, rock particles, and even small amounts of organic material. The most common gases found in comets include carbon dioxide, ammonia, and methane. Hydrocarbons and trace elements are present as well. Although comets are all made up of the same materials, the proportion of these materials differ.

comet with tail in space
Image Credit: Nazarii Neshcherenskyi, Shutterstock

What Is the Comet’s Tail Made Out Of?

The most breathtaking part of the comet is its tail. The tail is the bright light that trails behind the comet’s head. Comet tails come in two parts: the dust tail and the plasma tail¹. The dust tail is made up of tiny particles that reflect sunlight. These particles are from the head of the comet. The plasma tail turns blue because of how hot it is. It contains carbon monoxide ions.

Whenever you see a shooting star or a falling star¹, you are actually seeing the tail of the comet hitting the earth’s upper atmosphere and vaporizing. In other words, this beautiful sight is caused by the vaporization of dust and gas from the comet.

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Final Thoughts

Next time you see a comet, remember that you are looking at a dirty cosmic snowball. Much like the gross pile of snow beside a Zamboni parked outside a skating rink, comets are made up of different amounts of dirt, debris, ice, and gas.

Although the materials that make up a comet are pretty dirty when you think about it, comets are breathtaking from our point of view, especially as they approach the Sun, heat up, and develop long tails that sometimes turn into falling stars.

Featured Image Credit: Triff, Shutterstock

About the Author Robert Sparks

Robert’s obsession with all things optical started early in life, when his optician father would bring home prototypes for Robert to play with. Nowadays, Robert is dedicated to helping others find the right optics for their needs. His hobbies include astronomy, astrophysics, and model building. Originally from Newark, NJ, he resides in Santa Fe, New Mexico, where the nighttime skies are filled with glittering stars.