Eclipse News-Astronomers baffled by dark streaks across sky
New Millennium
August 13, 1999
Astronomers baffled by dark streaks across sky
Astronomers admitted yesterday that they are unable to explain a strange
phenomenon which appeared in the sky just before and after the total
eclipse.
Long, dark streaks across the sky baffled watchers, including people on
the Channel Island of Alderney. BBC Radio Guernsey was inundated with
calls yesterday morning from those who had witnessed them. One caller
said she had taken a video recording, but when she watched the tape
later, the streaks had vanished.
Prof Donald Lynden-Bell, an astronomer at Cambridge University, said the
bands appeared at right angles to the direction of the Moon's shadow. He
said: "It appeared to be a line across the sky and a darkening of the
cloud about two fingers wide. It struck me as odd."
Prof Mark Bailey, director of the Armagh Observatory in Northern
Ireland, said: "I haven't seen anything in the literature that could
explain it." Prof Lynden-Bell witnessed the spectacle some 20 minutes
before totality, and saw another band which stretched two thirds of the
way across the sky after totality.
Prof Phil Charles, of Oxford University, said: "I was taking wide-angle
pictures, looking with my 17mm lens, and I saw this dark band that went
across a large fraction of the sky. It puzzled me because it was roughly
perpendicular to the direction of the Moon's shadow."
Paul Sutherland, of the Society for Popular Astronomy, said: "It was
very strange. I didn't know what they were and I have been an amateur
astronomer for years." Some reported that the bands sank gradually
downwards.
Dr Simon Mitton, astronomy specialist at Cambridge University Press,
said the bands must have been shadows cast on to the low cloud by
condensation trails from the two Concordes which tracked the path of the
eclipse. "The uneclipsed Sun is very, very bright and normally there is
insufficient contrast for you to see the shadow of a high cloud being
cast on a lower one.
"The Sun's brightness is greatly turned down because of an eclipse -
which makes the contrast easier. Nobody has ever reported seeing this in
an eclipse. It is a rare meteorological phenomenon."
But Dr Helen Walker, of the Rutherford Appleton Laboratory, in
Oxfordshire, who saw four bands, dismissed this theory. She said: "This
was a uniform band of shadow and there was no shearing. You might get
one such trail, but not four." She believes it resulted from ice
crystals forming in the upper atmosphere due to the sudden drop in
temperature.