What you need to know about cloud backup

Diary marker This year, we have a rare chance to see the alpha Aurigids, the remnants of the ancient Comet Kiess.

On 1 September, the Earth will pass through an extremely fine band of dust and other debris left behind by Kiess when it passed the sun, way back in 83BC, which will light up the skies as the pieces tear into the atmosphere.

Meteor showers are the result of Earth passing through the trail of matter left behind when a comet approaches the sun, and crumbles and boils under its fierce glare. Most trails are left by short period comets, those that orbit the sun in less than 200 years, and have had a chance to build up into a broad band of shooting stars-in-waiting.

But the alpha Aurigids are almost unique because of Kiess' long orbital period. As it only passes near the sun every 2,000 years or so, its trail of cosmic breadcrumbs is very thin, meaning we pass through it much less frequently. Only one other meteor shower is known to be associated with a long-period comet.

Peter Jenniskens of NASA's Ames Research Centre, who along with Jérémie Vaubaillon at Caltech has calculated that we are in for a show, told NS that the band of debris is also influenced by Jupiter and Saturn's gravity, making it much harder to predict when it will return.

Speaking of short period comets, we must also note that this weekend will see the peak of the Perseid meteor showers. Of course, serious star-gazers will have been watching this show for weeks, but the merely star-curious might want to venture outside on Sunday night and tilt their eyes toward the heavens.

The Perseids are an annual show that begins towards the end of July as the Earth moves into the field of debris left behind by the tail of the comet Swift-Tuttle.

The showers are not expected to be anything like as exciting as in 2004, when we passed through a fresh strand of comet detritus and were treated to around 200 shooting stars every hour. But Reg staffers can confirm that the sky is being brightened, even now*, by the extraterrestrial fireworks, so Sunday night should be worth a look. ®

*Obviously, not in daylight

What you need to know about cloud backup