PERSEID FIREBALLS: Earth is entering a stream of debris from Comet Swift-Tuttle, source of the annual Perseid meteor shower. Peak rates of 100+ meteors per hour are expected next week when Earth approaches the heart of the debris stream. The display, however, is already underway. “Our network of meteor cameras has picked up more than 78 Perseid fireballs since July 27th,” reports Bill Cooke of NASA’s Meteoroid Environment Office. He prepared this solar system diagram showing the orbits of all the fireballs so far:
The green ellipses trace the orbits of Perseid meteoroids. They are a good match to the orbit of the parent comet, shown in purple.
“Comet debris particles a few cm wide are hitting the atmosphere with an average speed of 59.6 km/s (133,350 mph),” continues Cooke. “The average magnitude of the resulting fireballs is -3.7, about as bright as Venus.”
Cooke and colleagues have been monitoring fireball activity for years, and they have found that the Perseids produce more fireballs than any other annual shower.Check out their data.
“Comet Swift-Tuttle has a huge nucleus–about 26 km in diameter,” notes Cooke. “Most other comets are much smaller, with nuclei only a few kilometers across. As a result, Comet Swift-Tuttle produces a large number of meteoroids, many of which are hefty enough to produce fireballs.”
More fireballs are in the offing as Earth moves deeper into the debris stream of Comet Swift-Tuttle. Stay tuned!