Says Brian Marsden of the Smithsonian Institution's Minor Planet Center: "We're still not completely sure of the orbital period, but Comet Petriew might have passed close to Jupiter in 1982 -- an encounter that could have nudged the comet into its current orbit." Before 1982 Comet Petriew's orbit was probably bigger than it is now. It couldn't have come so close to Earth in decades past, which might explain why it was never spotted before.

Very long ago -- perhaps hundreds of millions of years -- Comet Petriew inhabited the Kuiper Belt, a doughnut-shaped cloud of dormant comets that circle the Sun beyond Neptune. Kuiper Belt comets tugged by the gravity of giant planets in the outer solar system can be nudged closer to the Sun, where they might eventually settle into orbits with periods of only a few years. Comet Petriew appears to be one of these, a short period object that will revisit the inner solar system frequently.

"The comet should be around magnitude 10.5 this weekend," says Petriew. After that it will slowly fade as it recedes from our planet, as well as from the Sun. If the comet is well-behaved, it should remain brighter than 11th magnitude through mid-September. "You will probably need a 6-inch telescope or larger to see it," he added, "although a very keen observer might spot it using a 4-inch."

No doubt plenty of astronomy enthusiasts will haul their telescopes outdoors in the weeks ahead to peer at the new comet. And perhaps some of them will scan the skies for comets of their own. It's worth a try. After all, Vance Petriew is living proof that not every comet's name is LINEAR.