Outbursts of comets - the case of 1P/Halley

It is examined whether the destruction of heterogeneous cometary grains can explain the variation of cometary brightness and comet outburst.Calculations were carried out for water ice grains with carbonoxideinclusions. It was shown that for realistic chosen values of parametersthe comet luminosity can increase by even a few stellar magnitudes.

The Destruction of Heterogeneous Cometary Grains as the Possible Cause of Variations and Outbursts of Comets' Brightness

Interaction between the strong solar wind and the dark side of a cometary nucleus was considered. It was calculated that the potential of the dark side of the cometary nucleus could be numerically large and negative. Assuming that the nucleus of the comet has surface mantle which consists of loose, fine dust-ice particles, it was shown that cometary particles could electrostatically levitate over the nucleus. It was examined how this phenomenon affected the changes in the cometary brightness. Calculations were carried out for realistically assumed values of a large range of cometary parameters. It was shown that the considered mechanism could lead to the variations of cometary brightness, sometimes even to the outbursts of brightness.

The Electrostatic Blow-Off of Cometary Grains and Variations and Outbursts of Brightness of Comets at Large Heliocentric Distances

Photoelectric photometry (UBV) of Comet P/Halley performed on April 29, 1986 has been presented. The observations show short-term variability in light. The amplitude of variability in U filter is much more than in B and V filters.

Variation in Comet P/Halley

The overall long-term behaviour of the total visual coma brightness of P/Halley during October 1982 – June 1986 is presented. The observations used in this study consist of the raw total magnitude data collected from the International Astronomical Union Circulars. We have compared the observed light curve with the predicted one.

The visual brightness behaviour of P/Halley during 1982–1986

The results of photometric measurements (in UBV filters) of Comet P/Halley during four nights in January 1986 have been presented. Rapid recurring increases of P/Halley's brightness were observed during these four nights. This phenomenon seemed to occur at a time interval of about 23.7 ± 0.3 hr. The maximum variation of brightness during an individual night amounts to δU ~ 0.m70; δB ~ 0.m, 65 and δV ~ 0.m66 in U, B, and V filters, respectively. Rapid irregular short-lived fluctuations of brightness of the order of 0.m1 were also found present during an individual night. The present observations show the active nature of P/Halley.

Rapid changes of brightness in P/Halley

Thirty photometric magnitudes, in each filter (UBV), of P/Halley (1982i) have been measured on 1986, January 12. They show short-term variability of about 0.15 magnitude. The present measurements show the active nature of the comet.

Wahab Uddin

Papers

Rapid changes of brightness in P/Halley

Brightness changes in P/Halley

Variation in Comet P/Halley