EXTRAORDINARY FIREBALL BURST SEEN BY IAA OBSERVERS AT DELAMONT COUNTRY PARK
AT 22.54 BST on 21-9-12 at Delamont Country Park, 1 mile south of Killyleagh in Co. Down, GPS coordinates 531113, 351190, 54deg22'56" N 5deg40'39" W, a group of 12 members from the Irish Astronomical Association during a regular observing session observed an amazing group of fireballs rising from trees 10 to 15 degrees above the eastern horizon to the right of Jupiter as seen from the main car park.
It was immediately thought they might be fireworks but they continued to rise vertically at a steady pace and fan out slightly as they approached us from distance, with their numbers increasing and their brilliant intensity remaining unchanged. The trail was between 3 and 4 degrees wide and 50 to 80 degrees long at zenith. We estimated approximately 20-30 fireballs were seen following the same east to west trajectory each with an estimated brightness between mag. -5 to -7 depending on size, and each left a small/medium trail as they travelled almost directly overhead.
The path of the fireballs was observed to the right of Aldebaran and M45 and rising vertically straight up past Alpha and Beta Cass'. At their highest point, they were some 5-8 degrees off vertical toward the eastern horizon. A group of 4 or 5 larger fireballs were at the front of the group and differences in size were apparent but each burned with a similar brightness and a distinct orange hue. After the fireballs passed the top of the summer triangle, 2 or possibly 3 sonic booms were heard before they passed to the left of the keystone of Hercules and set behind trees at approx 1 mile distance at 5 degrees above the western horizon.
We were able to observe the fireballs for approx’ 1min 30 sec to 2mins from the trees in the east to the trees in western horizon as we had particularly good views in that direction. As the fireballs approached the western horizon their brightness began to fade and their numbers dwindled, possibly due to burning up and/or atmospheric extinction, at least 2 or 3 were seen disappearing behind trees at mag.+1 or +2.
They were travelling at a speed somewhat faster than the ISS but perhaps not as fast as a typical meteorite on entry into the earths atmosphere. Their speed remained constant throughout.
David Stewart, IAA Observing Coordinator
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