TAURID FIREBALLS

Sky watchers should be alert for fireballs in the nights ahead. Forecasters say Earth might be heading for a swarm of gravelly debris from comet Encke. If so, meteoroids the size of pebbles and small stones hitting Earth's atmosphere at 25 km/s would produce a slow drizzle of very bright fireballs flying out of the constellation Taurus--hence the name "Taurids." The display is expected to peak with a few fireballs every hour during the nights of Nov. 5-12.

NASA's network of all-sky meteor cameras is already picking up some Taurid fireballs--"7 in the past two nights and 11 altogether since Halloween," reports Bill Cooke of the Meteoroid Environment Office. Here are their orbits: In the orbital diagram, the location of Earth is denoted by a red splat. The orbits of the meteoroids (yellow) roughly match that of parent Comet Encke (orange), confirming their association with the Taurid debris swarm.

"What always strikes me about the Taurids," notes Cooke, "is how deeply they penetrate Earth's atmosphere. On average, they make it to an altitude of 44 miles. Contrast this to the recent Orionids, which burn up at an average altitude of 58 miles. Part of this is due to the speed difference: Taurids are slow (27 km/s) while Orionids are fast (66 km/s). In addition, many Taurids are made up of stronger stuff than the Orionids." http://www.spaceweather.com