Another red spot, by Jove.

Attention, sky watchers. Jupiter has a second red spot.

Formally called Oval BA, it's about half the length of Jupiter's famous Great Red Spot, and nearly the same color. Oval BA derives from a trio of white storms discovered in the 1930s, which merged to form a single storm center in 2000.

The oval stayed white until December 2005, when it became brown. By February, Oval BA had turned red, reports amateur astronomer Christopher Go of Cebu, the Philippines. Scientists don't know whether its scarlet tinge will be permanent.

About twice as wide as Earth, Jupiter's Great Red Spot is the most powerful storm in the solar system and has remained red for at least 300 years. Scientists aren't sure why the Great Red Spot is red, notes planetary scientist Glenn Orton of NASA's Jet Propulsion Laboratory in Pasadena, Calif. A leading idea is that the storm is powerful enough to dredge sulfur-containing compounds or other materials from beneath the Jovian cloud tops and bring them to high altitudes. At such heights, ultraviolet light from the sun would turn some of the compounds red.

If the same explanation applies to Oval BA, it would indicate that this smaller storm has recently intensified and has begun to churn clouds at high altitudes.

Jupiter is now easy to find in the predawn sky. Before sunrise, look south and up; the planet is the brightest object. Viewers using telescopes with a mirror 10 inches across or larger and a digital camera should be able to track the new red spot.--R.C.