A spectacular outburst of shooting stars yesterday has given astronomers new information about what lies at the edge of the solar system.
Scientists had predicted that, on September 1, the Earth would run through a stream of debris ejected by an ancient comet as it passed close to the Sun about 2,000 years ago.
The celestial wanderer itself, called Comet Kiess, was next seen in 1911. Experts calculated that the dust cloud it threw off two millennia ago would move into our planet’s path this year.
The forecasts came after surprise meteor bursts were seen from the dust stream in 1935, 1986 and 1994. The peaks were short-lived but witnesses counted tens of brilliant meteors in just a few minutes.
The meteors were called the Aurigids because they appeared to radiate from the constellation of Auriga, the Charioteer, as they streamed into the atmosphere.
Meteor experts Esko Lyytinen, Peter Jenniskens and Jeremie Vaubaillon predicted that this year’s outburst would occur around 11.38 UT and be visible from the western USA and Pacific region shortly before dawn.
Stargazers who got up early to check the skies were rewarded with a fine display of meteors, though not in the hundreds that some were speculating. One blogger, for example, reported seeing 15 “really good ones” in half an hour which is a very healthy rate.
Peter Jenniskens, a research scientist with the Carl Sagan Center of the SETI Institute, flew with 23 colleagues aboard a Nasa Gulfstream jet to check on the shower and analyse what the meteors were made of by photographing their spectra.
Their flight over the Pacific was a great success and showed that the predictions for the outburst were remarkably accurate – it lasted at least two hours and peaked at around 11.15 UT, 18 minutes earlier than forecast.
Jenniskens said, on landing: “As expected, many Aurigids were as bright as the brighter stars on the sky. Some meteors were bluish or greenish in color, as reported for the 1994 return.
“Many, many meteors were recorded during the mission, and a large number of spectra were measured. This is the first time in history that an Aurigid shower was predicted, and the result has been a feast for data-starved astronomers.”
Astronomers believe the rare encounter with a long-period comet will tell them more about the make-up of Comet Kiess and deep-frozen material in the Oort cloud at the edge of the solar system, beyond Pluto.
Photo: Kat de Kleer, Nasa/Seti Institute.
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