Since comets are little more than snowballs blazing through space, you never know how spectacular they'll appear to viewers millions of miles distant.
But this week, in the western sky, folks in the Northern San Joaquin Valley could have what one local astronomer says is a once-in-a-decade opportunity: a chance to witness a comet with the naked eye, or at least with a simple pair of binoculars.
Comet Pan-STARRS is expected to put on its best showing tonight and Wednesday evening, immediately after sunset.
It might appear like an early evening star not far from the crescent moon.
Stockton astronomer Rick Mielbrecht said this could be the kind of astronomical event that might occur once every 10 years.
Then again, it might be cloudy this week. Or the comet -- which is on its maiden voyage around the sun, and has never been exposed to that kind of heat -- might melt.
"All the comet experts say the same thing: You just never know with comets," said Stockton Astronomical Society member Trevor Atkinson. "Basically, these things are just big icy snowballs coming from the outer reaches of the solar system. With some of them you get a long spectacular tail that's very easily visible to the naked eye every night for weeks, and some of them just fizzle."
Pan-STARRS is believed to have originated from the Oort Cloud, a comet breeding ground beyond Pluto.
Right now, Pan-STARRS is about 100 million miles from Earth as it travels inside the orbit of Mercury.
Despite the distance, you might be able to spot it. Find a place with few trees or other obstructions to the west. After the sun has fully set, train those binoculars on the area around the moon.
And if you miss it? No worries. A comet with even greater potential, known as Comet ISON, arrives in November. That comet might be visible to the naked eye even during the daytime, perhaps shining as brightly as a full moon.
Then again, as NASA put it, "Possibilities range from 'Comet of the Century' to 'disintegrated dud.' "
California astronomer Tony Phillips said the glare of the setting sun may make it difficult to see this wee's comet.
"All by itself, the slender moon will be super-beautiful. If you can see a comet right beside it ... what a bonus!" he wrote in an email from his home and observatory in the Sierra Nevada.
Next week, the comet should be easier to spot. It will be higher in the western sky and therefore visible for longer once the sun sets. The surrounding darkness, versus twilight, will make it stand out.
"Not a great comet, but still a pretty good one," Phillips noted.
The Associated Press contributed to this report.