Comets Vs. Asteroids: Are They the Same?

The classification of space matter is difficult to understand, especially if you’re new to astronomy. That’s because there’s different names for matter that seems to be made up of the same material. To further complicate matters, the matter often resembles each other, making it difficult to discern which is which. When it comes to asteroids and comets, they each have specific and unique characteristics which make it easier for scientists and astronomers to tell them apart but which might be more difficult to detect for the regular Joe. By narrowing down some of the basics, you can easily tell the difference between a comet and an asteroid, even with a human eye and without special astronomy equipment.

General characteristics. An asteroid is the label applied to a piece of space rock that orbits the sun in our solar system. Asteroids are broken off from other celestial bodies, like the moon and other planets.  Some asteroids can become so large that they have their own moons and are even classified as dwarf planets. Comets are much different. They’re actually pieces of ice that travel from much colder parts of the solar system toward the sun. They move so quickly and get hotter as they near the sun, resulting in a bright, fiery tail that can sometimes be seen by the human eye. While both asteroids and comets can be seen streaking through the night sky, asteroids become meteors when they enter Earth’s atmosphere, so it’s rare to see an asteroid without a telescope.

Notable bodies. The most famous asteroid is Ceres, which is classified as a planetoid or dwarf planet like Pluto. Ceres has its own moon and resides in the asteroid belt near Jupiter. It’s a quarter of the size of our moon, making it fairly large in asteroid terms. Since there’s millions of asteroids in the belt, larger ones like Ceres are the easiest to see and to classify. When it comes to comets, the most famous is probably Hailey’s Comet. Hailey’s Comet completes an orbit around the sun every 75 years and can be seen with the human eye, which accounts for its fame and popularity. The bright tail that follows it across the sky make it easy to spot and track as it makes its way toward the sun.

Parts and pieces. Asteroids are chunks of rock that also contain minerals and metals that have broken off from other planets and space matter. Asteroids are often pockmarked with craters, thanks to frequent collisions with other asteroids, moons and even planets over time. While some are round and smooth, others resemble a rock that you’d find on the ground here on Earth. Comets have distinct parts that can be easily seen and defined. The top of the comet is known as the coma, and it rounded and bright. The tail, which always points away from the sun, is the bright streak of light that follows the comet as it makes its way during orbit. A bright hydrogen cloud surrounds the nucleus, making the coma and the head of the comet easy to see.

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