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The Discovery of Comet Hale-Bopp



Alan Hale
September 1995

Ron Baalke has asked me to write this up in order to give readers an idea about who the discoverers of Comet Hale-Bopp are, and how we managed to find it.

Disclaimer: While I have not met Tom Bopp personally, I have had several phone conversations with him, and I feel like I know his side of the story well enough to tell it here. Obviously, I know myself and my side of the story better than I know his, and thus my stories below are longer than his, but this is not meant to slight his efforts in any way. Any serious errors or omissions in my descriptions of him or his discovery story belong to me.


I am a native New Mexican who has lived here most of my life, with the exception of four years in Maryland during the late 1970s and six years in California during the early and mid 1980s (including 2 1/2 years during which I worked at JPL in Pasadena). I am a professional astronomer who primarily specializes in the study of sunlike stars and the search for other planetary systems, although I have side interests in the fields of comets and near-Earth asteroids, and in the development of spaceflight. In addition, I have been an active amateur astronomer most of my life, concentrating primarily on the observation of comets, and have observed over 200 of these since I began doing so in 1970. I presently am head of an independent research and education organization, the Southwest Institute for Space Research, based in Cloudcroft, NM.

Tom Bopp lives in Glendale, Arizona, just outside of Phoenix. He presently works as a shift supervisor in the parts department of a construction materials company in Phoenix. He is an active amateur astronomer and has been an enthusiastic observer of deep-sky objects for over 25 years, both in Arizona and in his native Ohio.


[Our discovery stories are remarkably similar to each other, and to top it off, our discoveries were almost simultaneous; they were certainly within a few minutes of each other. In the below stories I am using local time, but please note that, while both New Mexico and Arizona are in the Mountain time zone, New Mexico "springs forward" to daylight savings time, and Arizona doesn't.)

During my normal study of comets it is my practice to observe comets once a week, on the average, and measure their brightnesses. On the night of July 22-23 -- the first clear night here in a week and a half -- I had planned to observe two comets. I finished with the first one -- Periodic Comet Clark -- shortly before midnight, and had about an hour and a half to wait before the second one -- Periodic Comet d'Arrest -- rose high enough in the east to get a good look at. I decided to pass the time by observing some deep-sky objects in Sagittarius, and when I turned my telescope (a Meade DS-16) to M70, I immediately noticed a fuzzy object in the field that hadn't been there when I had looked at M70 two weeks earlier. After verifying that I was indeed looking at M70, and not one of the many other globular clusters in that part of the sky, I checked the various deep-sky catalogues, then ran the comet-identification program at the IAU Central Bureau's computer in Cambridge, Massachusetts. I sent an email to Brian Marsden and Dan Green at the Central Bureau at that time informing them of a possible comet; later, when I had verified that the object had moved against the background stars, I sent them an additional email. I continued to follow the comet for a total of about 3 hours, until it set behind trees in the southwest, and then was able to email a detailed report, complete with two positions.

That same night Tom Bopp had traveled to Vekol Ranch, a desert dark-sky site near Stanfield, Arizona -- about 90 miles south of Phoenix -- along with several of his friends, a group which included Jim Stevens, Kevin Gill, Bernie Sanden, and a couple of others. They had planned to spend the night observing various deep-sky objects, and after awhile they were looking at some of the globular clusters in Sagittarius with -- among other instruments -- Stevens' home-built 17 1/2 inch Dobsonian reflector. Right around 11:00 PM they were looking at M70, and while Stevens was examining his star atlas to locate their next target, Bopp was watching through the eyepiece while the Earth's rotation carried M70 out of the field. At that time he noticed a fainter, fuzzy object coming into the field. [The comet was located 15 arcminutes east-northeast of M70 that night.] Bopp and his friends followed the object for the next hour, and after seeing it move relative to the background stars, concluded that they had a comet. Bopp then drove back to his home in Glendale, and sent a telegram to the Central Bureau informing them of his find.

IAU Circular 6187, announcing our discoveries, was issued about 12 hours later, and the rest is history . . .

Alan Hale
Cloudcroft, New Mexico

Additional Information About The Comet Hale-Bopp Discovery

red_dot.gif The Discoverers' Comments (Comet Observations Home Page - JPL)
red_dot.gif How the Comet was Discovered (

comethome.gif Comet Hale-Bopp Home Page