12/05/2021
Comets & Meteors
In this early morning photo, you can see C/2021 A1 ( ) in the upper left and a on the right. I'm often asked about the difference between comets and meteors since both objects appear similar in photographs. Size, distance, apparent motion, and longevity are the most significant distinguishing characteristics. Comets are large, typically several miles in diameter, while meteors are usually about the size of a rice grain. Comets are distant objects, normally getting no closer than tens of millions of miles away from Earth, while meteors are much closer at about 50 miles high in the upper atmosphere. Because of their large distance away, comets appear to move very slowly against the background of stars, shifting less than a few degrees from one night to the next. Due to their proximity, meteors appear to move much faster, traversing several degrees in about a second. Depending on how close they get to the sun, comets can last many thousands of years, while meteors are gone in the blink of an eye.
While comets and meteors are quite different, they are often closely related. Most meteors are the result of debris ejected from comets as they are heated by the sun. As these little bits of cometary material rain down on Earth at speeds of about 50,000 MPH, they interact with the atmosphere. As the meteor burns up it heats and ionizes the gases in the atmosphere, which causes the brief linear flash of light.
The meteor in this photo is likely part of the meteor shower, which peaks on December 13-14. Instead of a comet, this shower is the result of debris from an named 3200 Phaethon. Meteors resulting from asteroid debris tend to be brighter as they release more energy when they burn up. Asteroid 3200 is an odd one though. In some ways, it behaves more like a comet than an asteroid. For instance, it has a tail like a comet, and follows an orbit more typical of comets. Scientists are still trying to figure out its odd behavior.
