was probably the most widely observed and imaged comet of the
20th century, and one of the brightest seen for many decades.A
double exposure of Dorothy and Comet Hale Bopp at Tiki Beach in
Hale Bopp over Tiki Beach
John pointing out Hale Bopp. (As if it
needs pointing out!!!)
Hale–Bopp was discovered on July 23, 1995, separately by Alan Hale and Thomas Bopp prior
to it becoming naked-eye visible on Earth.
Although predicting the
maximum apparent brightness of new comets with any degree of certainty
Hale–Bopp met or exceeded most predictions when it passed perihelion on
April 1, 1997.
It was visible to the naked eye for a record
18 months, twice as long as the previous record holder, the Great Comet of 1811.
Accordingly, Hale–Bopp was dubbed the Great Comet of 1997.
The comet was discovered independently on July 23, 1995, by two observers, Alan Hale and Thomas Bopp, both in the United States.
Hale had spent many hundreds of hours searching for comets without success, and was tracking known comets from his driveway in New Mexico when he chanced upon Hale–Bopp just after midnight.
The comet had an apparent magnitude of 10.5 and lay near the globular cluster M70 in the constellation of Sagittarius.
Hale first established that there was no other deep-sky object near
M70, and then consulted a directory of known comets, finding that none
were known to be in this area of the sky.
Once he had established that
the object was moving relative to the background stars, he emailed the Central Bureau for Astronomical Telegrams, the clearing house for astronomical discoveries
Bopp did not own a telescope. He was out with friends near Stanfield, Arizona, observing star clusters and galaxies when
he chanced across the comet while at the eyepiece of his friend's
He realized he might have spotted something new when, like
Hale, he checked his star maps to determine if any other deep-sky
objects were known to be near M70, and found that there were none.
alerted the Central Bureau for Astronomical Telegrams through a Western Union telegram.
Brian G. Marsden,
who had run the bureau since 1968, laughed, "Nobody sends telegrams
anymore. I mean, by the time that telegram got here, Alan Hale had
already e-mailed us three times with updated coordinates."
The following morning, it was confirmed that this was a new comet, and
it was given the designation C/1995 O1. The discovery was announced in International Astronomical Union circular 6187
Hale–Bopp's orbital position was calculated as 7.2 astronomical units (AU) from the Sun, placing it between Jupiter and Saturn and by far the greatest distance from Earth at which a comet had been discovered by amateurs.
comets at this distance are extremely faint, and show no discernible
activity, but Hale–Bopp already had an observable coma.
An image taken at the Anglo-Australian Telescope in 1993 was found to show the then-unnoticed comet some 13 AU from the Sun, a distance at which most comets are essentially unobservable.
(Halley's Comet was more than 100 times fainter at the same distance from the Sun.)
Analysis indicated later that its comet nucleus was 60±20 kilometres in diameter, approximately six times the size of Halley.
Its great distance and surprising activity indicated that comet Hale–Bopp might become very bright indeed when it reached perihelion in
However, comet scientists were wary – comets can be extremely
unpredictable, and many have large outbursts at great distance only to
diminish in brightness later.
Comet Kohoutek in
1973 had been touted as a 'comet of the century' and turned out to be
unspectacular, as did Halley's Comet, 1P in 1986..
Hale–Bopp became visible to the naked eye in May 1996, and although its rate of brightening slowed considerably during the latter half of that year,
were still cautiously optimistic that it would become very bright.
was too closely aligned with the Sun to be observable during December
1996, but when it reappeared in January 1997
it was already bright
enough to be seen by anyone who looked for it, even from large cities
with light-polluted skies
The Internet was
a growing phenomenon at the time, and numerous websites that tracked
the comet's progress and provided daily images from around the world
became extremely popular.
The Internet played a large role in
encouraging the unprecedented public interest in comet Hale–Bopp
the comet approached the Sun, it continued to brighten, shining at
2nd magnitude in February, and showing a growing pair of tails,
The blue gas tail pointing straight away from the Sun and the yellowish dust tail curving away along its orbit.
On March 9, a solar eclipse in China, Mongolia and eastern Siberia allowed observers there to see the comet in the daytime.
Hale–Bopp had its closest approach to Earth on March 22, 1997, at a distance of 1.315 AU
As it passed perihelion on April 1, 1997, the comet developed into a
It shone brighter than any star in the sky except Sirius, and its dust tail stretched 40–45 degrees across the sky.
comet was visible well before the sky got fully dark each night, and
while many great comets are very close to the Sun as they pass
perihelion, comet Hale–Bopp was visible all night to northern hemisphere observers.
a trip to West Virgina I spotted Comet Hale Bopp in the trees with
binoculars and was able to show it to relatives even before it got dark
outside in the evening twilight.