The Extremely Active Comet C/Hale-Bopp (1995 O1): Production Rates from Nearly Five Years of Narrowband Photometry
Abstract
Comet C/Hale-Bopp (1995 O1) was an intrinsically bright object that exhibited the highest continuous gas and dust production rates ever measured for a comet. We will report on our extensive narrowband photometry observations of H-B, including 332 individual sets of photometry obtained on a total of 98 nights at Lowell and Perth Observatories. Our observations span nearly 5 years, beginning with inbound measurements on 1995 July 25 (heliocentric distance, r, of 7.14 AU), continuing through perihelion (1997 April 1; perihelion distance of 0.91 AU), then extending outbound until 2000 March 3 (r of 10.58 AU). A thorough analysis of this dataset has been delayed for numerous reasons, including the long timeline of post-perihelion observations and the calibrating of our then-new HB comet filter set (Farnham et al. 2000, Icarus 147, 180). We additionally discovered that, due to its extremely high production rates, the size of the collision zone for H-B was much larger than normal, especially near perihelion, requiring an adjustment to our standard scalelengths and an empirical adjustment to the derived water production rates. From our first observations, it was clear that H-B was unique. The dust production, even at 7.14 AU, had an Afρ of 50,000 cm - much higher than that measured for any comet in our database at any heliocentric distance. H-B's highest production rates were measured near perihelion, where Afρ peaked at 1.2×106 cm and the water production rate, also by far our highest value measured for any comet, reached 3.59×1031 molecules s-1. The effective active area required to produce the measured water production is 2100 km2, implying a minimum nucleus diameter of 26 km; however the existence of isolated jets strongly indicates that the entire surface of the nucleus is not active, which means the actual size is likely to be at least 2× as large. These and other results from this unique comet will be presented. This research has been supported by NASA's Planetary Astronomy Program.
- Publication:
-
AAS/Division for Planetary Sciences Meeting Abstracts #50
- Pub Date:
- October 2018
- Bibcode:
- 2018DPS....5021006B