Scientists reported that in the wee hours of July 14, dozens of meteors streaked across the dazzlingly clear starry sky over Maunakea, Hawaii. The event was broadcast to hundreds of people around the world with a Subaru Asahi camera.
“At first I thought it was just a series of small meteors,” Fukuro, an eyewitness, explained.
“But when I double-checked to count, I was amazed to notice that several small meteorites were visible simultaneously from the same direction.”
At 3:58 a.m. local time, all of these meteors flew out of the same point in the sky within 10 seconds. This is not the usual pattern seen during meteor showers, which usually appear more haphazardly in our skies as the Earth orbits the remnants of a comet’s tail.
An excited online discussion about the phenomenon alerted Subaru Telescope Camera Administrator Ichi Tnaka, who contacted astronomers who are now analyzing the data (thank the occasion that ordinary people were watching live, or we would never have heard about this event from astronomers).
“The scientific significance of capturing such a rare phenomenon is extremely high, and it is especially significant because the total duration of the event was longer than in previous cases,” said planetologist Junichi Watanabe, deputy director of the National Astronomical Observatory of Japan.
“The fact that the camera was located on Maunakea, one of the best observing sites in the world, was also an important factor in capturing such a rare event in addition to recent advances in camera technology.”
Since the phenomenon was first detected in 1997, only a handful of similar meteoroid clusters have been recorded, including one caught earlier this year by cameras at the University of Arizona in San Diego. This cluster of seven meteors occurred within 3 seconds of each other.
Watanabe and his colleagues described a mechanism to explain these kinds of meteor clusters back in 2003, based on data from the Leonida meteor showers.
The researchers calculated that in order for these pieces of space rock to appear so close together in time and distance in our sky, they would have had to have an unrealistically small difference in velocity between them – if they had cracked immediately or shortly after breaking away from the comet.
Instead, they conclude, this type of cluster is likely due to the fragmentation of meteoroids orbiting the Sun just before they reach Earth. The fragmentation of the meteoroids is probably caused by the additional heat they encounter when they reach the perihelion of their orbit (the closest point to the Sun), which must occur about every 33 years for Leonid meteoroids.
Information just obtained by the Subaru telescope may help clarify this question and possibly provide more information about the structure of meteoroids orbiting near us.