COSMOLOGY LAB FIREWORKS

COSMIC FIREWORKS

With lots of lawn seats filled an unusual comet puts on a show.

On a Saturday late last month, a speck of light shimmering in the shadows behind Jupiter erupted. And it keeps erupting, with two more jets of material firing into space on Sunday, then a fourth paroxysm on Monday.

As it raged and flared, it became 250 times as bright as usual.

This is not a distant tempestuous star, nor an effervescent world covered in erupting volcanoes. This is comet 29P. And it put on a show that anyone with a powerful backyard telescope could see.

What's causing this comet's riotous cascade ? '' We don't know,'' said Maria Womack, an astrophysicist at the National Science Foundation.

''And that's what makes it so interesting.''

Unlike most comets, Comet 29P does not plunge toward the sun before zipping back out to the solar system's outermost frontier. Instead, it revolves around the sun in the space between Jupiter and Saturn on a near-circular orbit, completing one circumnavigation every 14.6 years.

The comet is in a state of near-constant fury, blasting gas and dust into the enveloping dark. The hyperactivity is perhaps a result of its preponderance of carbon monoxide, which needs only a soupcon of sunlight to heat up and spew gas into space in large volumes.

There are at least seven brightening outbursts per year. But four consecutive outbursts in a few days took the exhibition to a new level.

These eruptions brighten our comet's atmosphere, or coma, by topping it up with sunlight-reflecting dust. [Robin George Andrews].