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Forum:Free Space
Topic:Space debris sighting over the UK? (Sept. 21)
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Bad Astronomy has more...

YankeeClipper
quote:
Originally posted by Blackarrow:
Did any space enthusiasts see this?
On Friday 21 Sep, circa 23:00 IST (22:00 UTC), I was at Dunsink Observatory here in North Dublin, Ireland, for Dublin Culture Night 2012. I was in line for a viewing through the 1868 12in refractor, when I first spotted this bright light through the dome shutters which were open to the North.

Running outside, we could clearly see a very prominent bright white/yellow meteoric fireball on an East to North-West downward trajectory. During the 15-20sec pass approx. 8-10 smaller yellow/orange lights disintegrated off the main body and trailed downward on the same trajectory before vanishing. Talk about spectacular !!

First thought was that it was either a meteor or a piece of large space debris such as a satellite on re-entry. The observed trajectory doesn't seem to support the theory of a de-orbiting decaying satellite, however, and there was no prior indication of any planned re-entry.

One way or another, it was the perfect spectacle for a night of astronomical observation

BlackarrowThe direction of travel seems to be a puzzle: most reports seem to suggest movement from east or northj-east to west or south-west. Is it plausible that two rocket stages, perhaps in roughly polar orbits, have collided and sprayed debris in odd directions? Are there any rocket-stages in a retrograde orbit? (For example, didn't Israel launch at least two satellites into retrograde orbit? Are any of the final stages still in orbit?)

Although meteors seem an easier explanation, the speed looks all wrong. How would Mr Occam wield his razor on this one?

Rick MulheirnI may have been a little off in my estimation of the direction of travel, but I have seen reports of sightings "directly overhead"... in Llandudno in North Wales.
YankeeClipper
quote:
Originally posted by Rick Mulheirn:
I have seen reports of sightings "directly overhead"... in Llandudno in North Wales.
Llandudno is due East of Dublin, so those reports are entirely consistent with my observation. My initial thought was that any debris may have impacted in the North-West of Ireland or Northern Ireland such was the trajectory.

Robert PearlmanIt wasn't space junk, but rather a meteor — and a historic one at that, Sky & Telescope reports.
For the first time ever, a meteor has grazed in and out of Earth's atmosphere, slowing enough to become a temporary satellite that lasted a full orbit...

Mathematician Esko Lyytinen, a member of the Finnish Fireball Working Group of the Ursa Astronomical Association, has analyzed both sets of sightings and concludes that the two events resulted from a single object encountering Earth that night. He believes a large body grazed the upper atmosphere, dipping to an altitude of 33 miles (53 km) over Ireland before escaping back to space. Because it arrived moving at only about 8 miles (13 km) per second, barely above Earth's escape velocity, it lingered for more than a minute as it crossed the sky. (This explains why some witnesses mistook it for reentering spacecraft debris.)

Lyytinen says the brief atmospheric passage took its toll. As the meteoroid broke apart, its velocity dropped to just 5.7 miles (9.2 km) per second, too slow to make an escape back to space. Instead, it became a temporary satellite of Earth, looping completely around the globe before reentering the atmosphere — this time for good. "It looks now that the fireball witnessed 155 minutes later in U.S. and Canada, may have been one fragment of the British fireball, most probably the biggest one," Lyytinen explains.

YankeeClipper
He believes a large body grazed the upper atmosphere, dipping to an altitude of 33 miles (53 km) over Ireland before escaping back to space.
That might explain why, as I was tracking this fireball downward, it seemed to just vanish in mid-air well-above the horizon. At the time I assumed it had just slowed/burnt up and any debris fallen to earth in the darkness.

domAs someone who lives under its path, should I consider this a lucky escape! Does he mention what would have happened if it hit... are we taking about a Tunguska-sized impact or much smaller?
Blackarrow
quote:
Originally posted by Blackarrow:
I doubt if this was meteor activity... Did any known satellite burn up last night?
I feel really stupid not correctly guessing that this was the first ever known example of a meteor grazing in and out of the atmosphere and becoming a temporary satellite of Earth for a single orbit. D'oh!
YankeeClipper
quote:
Originally posted by dom:
what would have happened if it hit... are we talking about a Tunguska-sized impact or much smaller?
Oh I don't know, depending on the location of the airburst/impact, a Tunguska-style event might have significantly improved the landscape especially in the Cavan border region

Now if you'll excuse me, I'm just going to put on my kevlar helmet, nomex flightsuit, kevlar/ceramic body armour, and climb into a bunker awaiting the flaming replies to that comment!

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