The comet was discovered as a 14th magnitude object on August 19th 1977 by Nikolaj Chernykh at the Crimean Astrophysical Observatory using their 40-cm astrograph (photographic telescope). The comet was found to be relatively distant from the Sun, having been discovered some 6 months before perihelion, which was at 2.57AU. The period was calculated to be 15.9 years. The comet was followed for 16 months
101P/Chernykh then split at its first return after discovery. The splitting was discovered by David Jewitt and Jane Luu with the 2.4-m telescope at Mauna Kea. The discovery was made in images from September 15th 1992 with fragment “B” already as far as an arcminute from the main nucleus, suggesting that the split had taken place some considerable time earlier. Once noticed, it was realised that the 19th magnitude fragment (3 magnitudes fainter than the main nucleus) had been recorded in images from September 7th 1992. Zdenek Sekanina investigated the split and found that it had taken place on April 14th 1991, more than 8 months before perihelion.
On many occasions when a nucleus splits the smaller fragment is seen only very briefly. However, component “B” was recovered at the 2005 return and initially was rather brighter relative to component “A” than the 3 magnitude difference seen in 1992.
101P suffers frequent close approaches with both Jupiter (1980 and 2102) and Saturn (1955, 2012 and 2042) at distances between 0.35 and 0.98AU leading to the possibility that component “B” could eventually migrate into a completely different orbit to “A”, although by 2104 the separation in perihelion time will be little more than 2 months. The effect of the perturbations is to reduce the perihelion distance progressively. From 2.68AU in 1929 it has now reduced to 2.35AU and, by 2104, with be down to 2.17AU, making the comet significantly brighter at a favourable opposition.
The 2005 return was well covered observationally with photometry from a large number of observers (MPC 213, 442, 945, A01, A02, A06, A10, A79, I77, J55, J64, J76 and J97). An interesting feature of the observations is the very rapid brightening of the comet in July and August 2005 as the geocentric distance decreased from 2.02AU to 1.61AU. Further approach to the Earth afterwards led to a show fade in the 10” aperture. Observations of 101P-b in December 2005, close to perihelion showed it to be only about 1.5 magnitudes fainter than 101P-a, although the fragment faded considerably in just 10 days around perihelion at the end of December 2005, suggesting that it had suffered an important outburst. Curiously, there are no observations of 101P-b from anywhere in the world before the end of November 2005, despite the fact that, by then, it should already have passed its maximum brightness, suggesting that there was a significant outburst about a month before perihelion.
The largest value of Afrho in a 10” aperture of 60-cm was registered approximately 110 days before perihelion. There is a small outburst in the light curve starting about 10 days after perihelion. However, the coma also became considerably more concentrated towards perihelion with the slope of the coma much steeper than 1/r making comparison of Afrho in different apertures somewhat risky, although the physical size of the 10” aperture varied very little for most of the apparition.
Although there is some dispersion in the data, we can see that the slope of the coma, as determined from multiaperture photometry, was significantly steeper than 1/r by the end of the apparition, meaning that the coma was more concentrated than a 1/r profile.