NASA is preparing to use the Hubble Space Telescope to observe an incredible celestial spectacle: a gargantuan storm on Saturn that is 11/2 times wider than Earth.

"It's creating a lot of excitement. As soon as the space telescope people heard about it, they wanted to point the telescope at it," said Daniel Green of the International Astronomical Union's Central Bureau for Astronomical Telegrams, a reporting agency for discoveries in space.The oval white spot on the solar system's second-largest planet is growing and now measures 12,500 miles wide by 3,100 miles long, New Mexico State University astronomer Reta Beebe said Tuesday.

"It's lovely," she said by phone from Las Cruces, N.M.

By comparison, Earth has a diameter of about 7,900 miles. Jupiter's Great Red Spot, which also is a storm, measures roughly 18,600 miles by 8,700 miles.

Giant white spots near the equator were observed in 1876, 1903, 1933 and 1960, but only the 1933 spot approached the size of the current one, scientists said.

"I'm ecstatic. It's really incredible," said Stephen O'Meara, an associate editor at Sky and Telescope magazine in Cambridge, Mass.

NASA's $1.5 billion Hubble telescope will be used to study the storm early next month if it hasn't disappeared by then, said Rodger Doxsey, science and engineering systems chief at the Space Telescope Science Institute, the organization that schedules observations with the Hubble.