Most comets at this distance are extremely faint, and show no discernible activity, but Hale–Bopp already had an observable coma. 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. The discovery was announced in International Astronomical Union circular 6187. The following morning, it was confirmed that this was a new comet, and it was given the designation C/1995 O1.
I mean, by the time that telegram got here, Alan Hale had already e-mailed us three times with updated coordinates." Marsden, who had run the bureau since 1968, laughed, "Nobody sends telegrams anymore. He alerted the Central Bureau for Astronomical Telegrams through a Western Union telegram. 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. 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 telescope. 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. 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. The comet had an apparent magnitude of 10.5 and lay near the globular cluster M70 in the constellation of Sagittarius. 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 was discovered independently on July 23, 1995, by two observers, Alan Hale and Thomas Bopp, both in the United States. Accordingly, Hale–Bopp was dubbed the great comet of 1997. It was visible to the naked eye for a record 18 months, twice as long as the Great Comet of 1811, the previous record holder.
It is difficult to predict the maximum brightness of new comets with any degree of certainty, but Hale–Bopp met and exceeded most predictions when it passed perihelion on April 1, 1997, reaching about magnitude −1.8. Comet Hale–Bopp, shortly after passing perihelion in April 1997Ĭomet Hale–Bopp (formally designated C/1995 O1) is a comet that was one of the most widely observed of the 20th century and one of the brightest seen for many decades.Īlan Hale and Thomas Bopp discovered Comet Hale–Bopp separately on July 23, 1995, before it became visible to the naked eye.