THE SUN
▼The lovely Diamond
Ring effect,seen just before
and just after totality.
This photograph was taken
from Java on 11 June 1983
by Dr Bill Livingston.Quiescent prominences may hang in the chromosphere for
many weeks, but eruptive prominences show violent
motion, often rising to thousands of kilometres; in some
cases material is hurled away from the Sun altogether.
They can be seen with the naked eye only during totality,
but spectroscopic equipment now makes it possible for
them to be studied at any time. By observing in hydrogen
light, prominences may also be seen against the bright
disk as dark filaments, sometimes termed flocculi. (Bright
flocculi are due to calcium.)
Shadow bands are wavy lines seen across the Earth’s
surface just before and just after totality. They are due to
effects in the atmosphere, and are remarkably difficult to
photograph well; neither are they seen at every total eclipse.
During totality, the scene is dominated by the glorious
pearly corona, which stretches outwards from the Sun in all
directions; at times of spot-maxima it is reasonably symmet-
rical, but near spot-minimum there are long streamers. It is
extremely rarefied, with a density less than one million-
millionth of that of the Earth’s air at sea level. Its tempera-
ture is well over a million degrees, but this does not indicate
that it sends out much heat. Scientifically, temperature is
measured by the speeds at which the various atoms and
molecules move around; the greater the speeds, the higher
the temperature. In the corona the speeds are very high,
but there are so few particles that the heat is negligible.
The cause of the high temperature seems to be linked with
magnetic phenomena, though it is not yet fully understood.
Eclipse photography is fascinating, but there is one
point to be borne in mind. Though it is quite safe to look
directly at the totally eclipsed Sun, the slightest trace of
the photosphere means that the danger returns, and it is
essential to remember that pointing an SLR camera at the
Sun is tantamount to using a telescope. As always, the
greatest care must be taken – but nobody should ever pass
up the chance of seeing the splendour of a total solar eclipse.▼The annular eclipse of
10 May 1994, photographed
by the author from Mexico. The partial eclipse
of 21 November 1966
photographed from Sussex
by Henry Brinton with a
10-cm (4-inch) reflector. Total eclipse, 11 July 1981;
photographed by Akira Fujii.
The corona was
magnificently displayed. The
shape of the corona varies
according to the state of the
solar cycle; near spot-
maximum it is fairly regular,
while near spot-minimum
long streamers extend fromthe equatorial regions.
During totality the sky
darkens and planets and
bright stars may be seen.
Before the Space Age, total
eclipses were of the utmost
importance to physicists,
because there were no other
opportunities to observe the
outer corona.E152-191 UNIVERSE UK 2003mb 7/4/03 5:42 pm Page 161