Comet pan-STARRS C/2011L4 and comet ISON dates, schedule: Two comets to light up skies this year

In what should be a stargazer's delight, two of the brightest comets to be seen from Earth in the past three centuries will grace the night skies later this year.

The first, called pan-STARRS C/2011L4, is expected to arrive March 8 and remain visible for about a week in the western sky after sunset.

The second, called ISON, even brighter, is scheduled to make an appearance shortly after Thanksgiving and linger into December. It will be seen in the eastern sky in the early-morning hours.

"It's the year of the comet," said Eric Vandernoot, astronomy coordinator at Florida Atlantic University in Boca Raton. "Both should be really cool."

The reason both will be so bright: Both will draw extremely close to the sun, and it's the sun's light reflecting off the comets' vaporous gases and clouds that make for spectacular viewing, said Bill Dishong, producer of the PBS television show "Stargazers."

The pan-STARRS comet will slide within 30 million miles of the sun, or even closer than the planet Mercury's orbit. ISON will sneak within 9 million miles, so close that it could potentially disintegrate from the heat.

"What we'll see is like a big tail, pointing up from the horizon," said Dishong, who has worked at the Miami Museum of Science and Planetarium for 43 years. "The tail can be fan-shaped or linear. Sometimes you can even get fingers, or parallel streaks."

However, "bright" is a relative term, he noted. He said the only way to clearly see either comet is far from city lights, for instance out on Alligator Alley or in the northern part of the state. In addition, clouds and other weather conditions could hamper the show.

"If you really want to see them, plan a trip to Vail," he said, referring to the Colorado ski resort.

While the best way to see the comets is with the naked eye, planetariums still plan to offer public viewing with telescopes.