Did that comet have a name?
Lug/Lugh or Cuchulinn, son of Lug/Lugh. (It may have been just a close flyby comet). I'm quoting Mike Baillie. ( I believe this is also referenced in Clube and Napiers book, Cosmic Winter and another book titled Catasthrophe.)
Updated 12:40 PM ET September 8, 2000
LONDON (Reuters) - Something catastrophic occurred on Earth 1,500 years ago that may have led to the Dark Ages and coincided with the end of the Roman Empire and the death of King Arthur, a Northern Ireland scientist said Friday. It could have been a bombardment of cometary debris or the eruption of a super volcano.
But whatever it was, it is clearly etched in the chronology of tree rings from around the world, according to Professor Mike Baillie, of Queen's University in Belfast.
The global environmental event that occurred around 540 AD is not recorded in any history books. But the tree ring chronologies compiled from samples of trees, some preserved in bogs, which date back thousands of years, single out something that was quite extraordinary.
"It was a catastrophic environmental downturn that shows up in trees all over the world," Baillie told a news conference at the British Association for the Advancement of Science conference. "This event is clear in the tree ring records."
(The 540AD event is not recorded, dust/acid layer, in the ice core samples. That's the source of the comet speculation)
">The comet that plunged into the Celtic Sea in 540AD and brought on the Dark Ages
Did that comet have a name?"
That's not what brought on the dark ages. It was the collapse of Roman civilisation and the growing darkness of superstition and paganism of the ruling Catholic Church.