Also known as the Great Comet of 1997, this impressive
fireball can
already be seen blazing across the sky, although you have
to get up
an hour or two before sunrise to see it. If you're not
an early bird,
wait until the end of March, when the comet will be at
its brightest
and visible to the naked eye just after sunset.
Comet Hale-Bopp briefly became the subject of a bizarre
controversy
late last year when an amateur astronomer in Texas took
a photo of it
through a telescope which seemed to show it was being
accompanied by
a large ''Saturn-like object".
There was some conjecture that the ''dirty snowball" which
forms the
comet's nucleus had broken up into clumps. The subject
was taken up
by a radio talk-show host, and then by UFO enthusiasts
who speculated
that the comet was being accompanied by a massive alien
spaceship.
Don't run for the hills just yet, however, because the
whole
controversy was soon exposed as a hoax. Pictures displayed
on the
Internet purporting to show the accompanying object were
deemed to be
the result of photographic errors, if not outright deceit.
In fact, the appearance of Comet Hale-Bopp is exciting
enough on its
own. It was first sighted by US astronomers Alan Hale
and Thomas Bopp
in 1995 when it was still outside the orbit of Jupiter
the furthest
any comet has ever been discovered. Its brightness was
startling a
thousand times more brilliant than Halley's Comet at the
same
distance.
These first sightings suggested the comet would put on
a great show
as it approached the Earth and Sun this year, and perhaps
even be
visible in daylight. As further data was obtained, those
expectations have
been toned down, but the comet should still shine as brightly
as some
of the brightest stars. Scientists are particularly interested
in
comets because, as remnants of the early solar system,
they can tell
us a bit about what the planets were like when first formed.
In fact,
comets may even hold the key to the origins of life, as
they are
thought to have seeded Earth with some molecules important
to life's
formation.
Hale-Bopp is a relatively large comet its nucleus
is estimated to
have a diameter of 40 kilometres, roughly four times the
size of
Halley's Comet travelling on a long, elliptical
orbit around the
sun. It has passed this way before, a few thousand years
ago.
The sublimating snowball has been zooming up from below the plane
of the
solar system, and is now arcing over the top of the Sun,
to which it
will make its closest approach on April 1, before dropping
back down
into the nether regions of space.
Currently about 240 million kilometres from the Earth,
Comet
Hale-Bopp will not get much closer. It will approach to
within about 194
million km on April 22, but that is still roughly 1.3
times farther than the
Sun is from the Earth. By comparison, Comet Hyakutake
last year came
within 17 million km of the Earth.
One of the more unusual features of Comet Hale-Bopp are
its jets,
long fountains of gas and debris which spurt out of the nucleus as the Sun
burns off the outer layers of ice.
Although the jets in themselves are not unusual, Hale-Bopp
seems to
have many of them and they have been ''turned on" quite
a long way
from the Sun.
Determined comet-spotters can catch a sight of the fireball
by waking
up before dawn and looking low in the sky for a ''fuzzy
star" just
north of due east. It is near the constellation Cygnus,
which is said
to form the shape of a swan but actually looks like a
cross.
The best dates to view the comet will be between March
26 and April
12, when it will rise in the northwest after sunset. Even
in Bangkok,
Hale-Bopp should be visible to the naked eye, complete
with an
elegant tail.
Actually, viewers might get an extra-special treat as the
person with
the best view of the comet astronaut Steve Hawley
aboard the
orbiting space shuttle Discovery reported last week
that Hale-Bopp
had two magnificent tails.