AAO image reference AAT 46. « Previous || Next »
Top left is NE. Image width is about 44 arc min
Image and text © 1985-2002, Anglo-Australian Observatory, photograph by David Malin.
Almost all the colour pictures from the AAT are made by combining three black and white photographs taken in red, blue and green light. Most of the objects are very distant and plates taken years apart show little change; however Halley's Comet moved rapidly through the solar system towards the sun and as the telescope followed its motion the background stars were recorded as coloured streaks, their length corresponding to the exposure times, (15, 15 and 20 minutes). The diffuse coma is tinged blue by the action of sunlight on gases evaporated from the icy nucleus, leaving behind tiny dust grains as a faint yellow tail shining by reflected sunlight.
The other images of Comet Halley (below) show it after perihelion passage (after its closest approach to the sun).
Related images, other comets
AAT 117. Halley's Comet, April 9-10, 1986 (AAT image)
UKS 19. The tails of Comet Halley on 12 March, 1986
UKS 34. Halley's Comet on April 9-10, 1986
UKS 33. Comet Hyukatake, March, 1996
MISC 20. Comet Halley hanging in the Milky Way in 1986.
B&W image Features in the dust tail of Comet Halley, 12 March, 1986
For details of photographic exposure, search technical table by AAT reference number