Ian Halliday

Millimeter and submillimeter observations of the asteroid 4 Vesta

Precise and well-calibrated observations made with the James Clerk Maxwell Telescope are presented of the submillimeter thermal spectrum and light curve of the asteroid 4 Vesta. The disk-averaged Rayleigh-Jeans temperature is as low or lower at submillimeter wavelengths as it is at centimeter wavelengths. Although the interpretation of the spectrum is ambiguous, it seems to indicate the presence of a dusty, porous regolith. At 1 mm wavelength the rotational light curve of Vesta appears double peaked over the 5.342 hr rotation period, unlike the optical lightcurve which is single peaked

The near-infra-red spectrum of meteors☆

Abstract The photographic infra-red spectra of nine meteors are studied. A total of 15 atomic emission lines are identified in the infra-red region, due to NI, OI, and CaII. As yet no infra-red lines have been observed in the spectra of slow meteors. The lines due to CaII become enhanced relative to lines of NI and OI with increasing luminosity of the meteor.

One-Millimeter Observations of Asteroids with the James Clerk Maxwell Telescope

Five asteroids (1 Ceres, 2 Pallas, 3 Juno, 18 Melpomene, and 444 Gyptis) have been observed at 1100µm, with an additional measurement of 1 Ceres at 800µm. These are the first radiofrequency observations ever reported for 3 Juno, 18 Melpomene, and 444 Gyptis, and the highest radio frequency observations reported for 1 Ceres and 2 Pallas.

Origin and Evolution of Interplanetary Objects

A brief summary is given of the current concepts of the icy conglomerate cometary nucleus and of the origin of comets. Evidence that the cores of comets may contain less than average volatile material, wheter in formation or by radiative heating, raises the question of why at least two very faint short-period comets suddenly experienced violent outbursts (~4000 times in brightness). A preliminary study of close double comet nuclei as affected by differential nongravitational forces shows that a collision of a cometary satellite with its primary is a likely outcome. Thus double nuclei may possibly explain these rare but extreme outbrusts. Statistics suggest, however that most comet splitting and comet outbursts represent instrinsic activities in extremely non-homogeneous nuclei.