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Mon. Not. R. Astron. Soc. 355, 191195 (2004) doi:10.1111/j.1365-2966.2004.08309.x Extreme albedo comets and the impact hazard
 

Summary: Mon. Not. R. Astron. Soc. 355, 191195 (2004) doi:10.1111/j.1365-2966.2004.08309.x
Extreme albedo comets and the impact hazard
W. M. Napier,1,2
J. T. Wickramasinghe2
and N. C. Wickramasinghe2
1Armagh Observatory, College Hill, Armagh, Northern Ireland BT61 9DG
2Cardiff Centre for Astrobiology, Cardiff University, 2 North Road, Cardiff CF10 3DY
Accepted 2004 August 12. Received 2004 August 12; in original form 2004 April 21
ABSTRACT
Dynamical balance arguments that involve the capture of long-period comets from the Oort
cloud imply that there should be 1000 times more Halley-type objects than are actually
observed. If the active comets rapidly become dormant, with albedos comparable to those of
known cometary surfaces, hundreds of such bodies should by now have been detected whereas
in fact only a few have been found. If, on the other hand, they disintegrate to dust, we show
here that the debris would create a bright, near-spherical zodiacal cloud and 1530 strong
annual meteor showers, also contrary to observation. Here we demonstrate that the surfaces
of inactive comets, if composed of loose, fluffy organic material like cometary meteoroids,
develop reflectivities that are vanishingly small in visible light. The near-Earth objects may
therefore be dominated by a population of fast, multi-kilometre bodies too dark to be seen
with current near-Earth object surveys. Deflection strategies that assume decades or centuries

  

Source: Armagh Observatory

 

Collections: Physics