A Comet's Tale


Aaron Calhoun

Guest Columnist


Imagine what it would be like being a comet.

You live in a place called the Oort Cloud, a vast sphere composed of trillions of other comets located almost halfway from the Sun to the next-nearest star. You have plenty of neighbors out there – but the neighborhood is so large, and so far away, that the Sun is just a bright speck and your nearest neighbor is about as far away as Saturn is from the Sun.

It’s dark out here, and you’re alone and cold. But the cold doesn’t bother you because you’re a “dirty snowball” composed of ice and dust. You don’t know your name – and you may never have one, most comets don’t – but you know what you’re doing out there: you’re waiting. You just don’t know what you’re waiting for.

Suddenly, you feel a push. You don’t know what’s pushing you – it could be the radiation pressure from a passing star, or the Milky Way’s tidal effect on the Oort Cloud – but none of that matters. What matters is that suddenly you’re moving toward that tiny, bright speck in the sky.

Three million years later, you’re still moving toward that speck, which has grown considerably in size, brightness and warmth. You’re in the realm of the planets now, and their gravitational effects will change your life forever. (As if it hasn’t already been changed!)

Eventually, people living on planet Earth notice you, and they give you a name and a nickname. Your name is Comet C/2013 US 10, and your nickname Comet Catalina. You were nicknamed after the group that discovered you in 2013, the Catalina Sky Survey.

When you reached your closest point to the Sun – 76 million miles – on November 15, you were traveling 104,000 mph. And that was fine with you: it was a very hot time. You never developed a long dust tail, but you sweated off a lot of weight.

Your original path to the Sun would have put you in a solar orbit that would bring you back every few million years, but the planets changed all that. Due to their gravitational tugs, you’re now on an “ejection trajectory,” which means that you won’t be back. Ever. You’re destined to spend the rest of time as a lonely little snowball wandering around the vastness of space. So anybody who wants to see you needs to do it now. You’ll move out of their view after January.

The closest you’ll ever come to Earth will be 67 million miles on January 17. You’ll be a fuzzy little ball of light shining at 5th magnitude in binoculars or a small telescope in the pre-dawn eastern sky until January 7. After that, you’ll rise after midnight until the end of January, growing ever dimmer with each passing night.


Aaron Calhoun is a member of the Flint River Astronomy Club which serves Spalding and surrounding counties.