Near Earth Objects: All About Asteroids, Meteors, and Comets

Updated on September 6, 2019
harrynielsen profile image

Science has always fascinated me. This includes not only the ecological sciences, which I studied in school, but other endeavors, as well.

No comet has struck the earth in recent memory, but a strike is not out of the question.
No comet has struck the earth in recent memory, but a strike is not out of the question.

View From Planet Earth

As any stargazer will tell you, our solar system is an active place. Not only is there the movement of the planets around the sun and the various moons around their respective planets, but also, there are a host of smaller objects, which follow their own trajectory around the sun. Most of these fast-moving bits of debris are not visible to the naked eye, but there are a few exceptions.

Most spectacular would be the comets, as they swing around the sun and in doing so produce long showy tails, sometimes visible with the naked eye. Recently, these space travelers along with asteroids have come under increased scrutiny, as we realize that the possibility of an earth strike may be greater than previously thought. When any of these objects gets close to the earth, they are labeled as Near Earth Objects or NEOs.



Comets have been most aptly described by space scientists as dirty snowballs (or perhaps snowy dirtballs), traveling through space at a high rate of speed.

Comets are composed of three parts; a head (or nucleus), a coma and a tail. The head is a concentrated conglomerate of ice, dust, and small rocky particles that form the core and is the densest part of the comet. Streaming out from the head there is usually (but not always) a small circular, coma and then a long, showy tail. The coma is likened to the atmosphere of a planet, as it is a collection of dust and gases that streams out from the nucleus. Further out from the main part of the comet, dust trails can be seen streaming far away from the head. This is the tail of the comet.

Space Rocks Passing Close By Planet Earth

Concerns of asteroids passing close by or actually striking our planet, have become a growing concern among space scientists
Concerns of asteroids passing close by or actually striking our planet, have become a growing concern among space scientists


Besides comets, there is another kind of space object that orbits the sun. These are space rocks that seldom form tails, like a comet. They are named asteroids and can vary in size from a piece of rock, smaller than your fist, to large objects that measure several kilometers across. The large ones concern modern scientists the most, for it's believed that even a close pass-by could possibly set off ripple effects on earth's surface. At present, scientists are not tracking any asteroids that they believe could hit the earth, directly.

Meteroids, Meteors and Meteorites

When asteroids are traveling through space, sometimes they collide. This may sound strange at first, but when you figure that there are millions of asteroids in our solar system and that most of these objects maintain a circular orbit that usually keeps them inside the path of Jupiter, then all of a sudden, the likelihood of an asteroid collision seems much higher. And when asteroids collide, smaller pieces break off.

These pieces are called meteroids. If one of these meteroids, enters our atmosphere, it becomes a bright light streaking across the sky, called a meteor. And if a meteor, makes it through the atmosphere without burning up and strikes ground, then that object is now called a meteorite.

Most of these objects are two small to be tracked by our space instruments, so they are not referred to as Near Earth Objects. However, it is possible for a meteor to explode, as it is traveling through the atmosphere and on rare occasion that explosion can create property damage on earth or even human injury.

A Cigar-shaped Visitor from Another Solar System

The unusual cigar shape of this asteroid had a few observers speculating about extra-terrestrial visitors, image from ESO
The unusual cigar shape of this asteroid had a few observers speculating about extra-terrestrial visitors, image from ESO

An Interstellar Visitor Named Oumuamua

Late in 2017 an interstellar asteroid, traveling at a very high rate of speed, passed within 15 million miles of earth. Though never a threat to actually hit our planet, the long distance traveler is now headed away from the sun and once it leaves our solar sytem, Oumuamua will not return again.

Still, its appearance in our solar system has caught the attention of many scientist and lay observers, for this is the first time that such a space object has been tracked by our observation eqipment.

Snow in Hawaii

Winter at the Haleakala Observatory on top of Hawaii's tallest mountain, can involve snow
Winter at the Haleakala Observatory on top of Hawaii's tallest mountain, can involve snow

What Is Pan-STARRS?

Pan-STARRS or the Panoramic Survey Telescope and Rapid Response System, is an integral part of the Near Earth Object Observation Project that was established by NASA in 2008. It is a complex, physical system of telescopes, astronomical cameras and computers, located at the Haleakala Observatory, which is situated high in the volcanic mountains of Hawaii.

The purpose of Pan-STARRS is to locate, track and provide emergency information, if needed, when an extra-terrestrial object, such as a comet or asteroid comes close to our planet. Pan-STARRS was instrumental in finding and tracking Oumuamua, that interstellar asteroid, which recently captured the attention of many astronomers and amateur sky observers. Fortunately, Oumuamua, which means "a messenger from afar arriving first" in the Hawiian language, flew by without so much as a ripple in the ocean and is now headed safely out of our solar system.

How You Can Keep Track of Near Earth Objects

Purchasing telescopes that can pick up Near Earth Objects is probably beyond the financial means of most people. Fortunately, there is an easy to use alternative, which can help you stay informed on any threats that these space objects might pose to our planet Earth. All you have to do is go here and sign up for twitter alerts from NASA's Jet Propulsion Laboratory. When ever a space object approaches, the good folks at JPL will kindly let you know.

A Fragile Existence

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2018 Harry Nielsen


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    • harrynielsen profile imageAUTHOR

      Harry Nielsen 

      2 years ago from Durango, Colorado

      Actually, they are different names and change of states for the same object, as it breaks off from a larger piece of space rock, possibly enters the earth's atmosphere and possibly hits the earth's surface. In other words, a meteorite was once a meteor. And a meteor was once a meteoroid.

    • K S Lane profile image

      K S Lane 

      2 years ago from Melbourne, Australia

      I had no idea that meteors, meteoroids and meteorites were different things! I suppose I just always assumed that they were different words that described the same thing- thanks for educating me!


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