Today Comet Hale-Bopp has reached its maximum extent in the history of astronomy.
Comet Hale–Bopp was discovered in July 1995, and about two years later it reached its peak, breaking records for the period. Credit: E. Kolmhofer, H. Raab; Johannes-Kepler-Observatory, Linz, Austria (https://sernwarte.at), CC BY-SA 3.0, via Wikimedia Commons
American astronomer Alan Hale, observing from Cloudcroft, New Mexico, and American amateur astronomer Thomas Bopp, observing near Stanfield, Arizona, independently discovered Comet Hale–Bopp on July 23, 1995. Both observers were looking at the globular cluster M70 in Sagittarius and spotted the comet nearby. Orbital calculations showed that on the night they found it, Hale–Bopp was about 7.2 astronomical units away from the Sun, about twice the normal discovery distance for comets. (An astronomical unit, or AU, is the average distance between Earth and the Sun.)
Fortunately, unlike Comet Kohoutek, Comet Hale-Bopp brightened according to predictions. It first became visible to the naked eye from the darkest places on May 17, 1996, and remained so for 18 months, surpassing the old record of nine months set by the Great Comet of 1811. Hale–Bopp reached magnitude 0 on March 7, 1997. Two weeks later, on March 22, it reached magnitude −0.8, brighter than any star except Sirius (Alpha). [α] Canis Majoris), whose tail extended approximately 20°. It was last seen with the naked eye on December 9, 1997.
To say that Hale-Bopp is a long-period comet seems to be a bit of an understatement. Its previous perihelion was in July 2215 BC, when it would have been observed over Egypt. It will next reach perihelion in 4385 or so.
