Comet Enthusiast

September 14, 2010

Planetary behemoth Jupiter will shine bigger and brighter September 21 than it has in almost 50 years. That's when it lies at opposition, putting it directly opposite the Sun in Earth's sky. On the 21st, the jovian giant will rise at sunset, set at sunrise, and remain visible all night.

This opposition is special because Jupiter, the largest of all the solar system's planets, will soon reach perihelion, the closest point in its orbit to the Sun. That means it's physically closer to Earth during this opposition than a normal one. It will rise below the Circlet asterism in the constellation Pisces the Fish and present its best views high in the sky, when its light travels through less of Earth's atmosphere.

"It'll be a wonderful show this year," said Michael E. Bakich, Astronomy senior editor. "Jupiter is a great target for beginning observers and old pros alike, and it won't get better than this. You'll easily spot its orbiting moons and its northern cloud belt."

The unexpected disappearance of Jupiter's South Equatorial Belt (SEB) earlier this year also makes this opposition unusual. The SEB has vanished from sight before, and its return is often impressive, with dramatic storms erupting suddenly. It may be days or years before Jupiter again looks "normal," just one more reason observers should target the king of planets.

At its nearest, Jupiter will sparkle at magnitude -2.9, and its equator will span 49.9", making it hard to ignore. "Fans of Jupiter won't want to miss it," Bakich said.