New measurements of the hemispherical albedo of cometary analogues: Influence on the amplitude of the change of cometary brightness during its outburst

Abstract

The paper presents new experimental results of measurements of the hemispherical albedo of a potential comet analogue and an analysis of its influence on the change in the cometary brightness. Measurements of the spectral properties of the tested analogues were performed using a Cary 5000 spectrometer in the wavelength range from 200 to 2500 nm. Two samples were used as a dust analogue: a mixture of sand and ash (sample A) and a mixture of sand and charcoal (sample B), respectively. The obtained hemispherical albedo values for the tested samples ranged from 1.20% to 32.25%. In particular, for sample B, the obtained hemispherical albedo values are comparable to the actual reflectance for comet 67P. Based on the obtained spectral properties of the tested samples, a thermodynamic model of cometary activity was developed and used, among others, to calculate the power absorbed by the tested analogue and the sublimation flux occurring through the porous structure of the fine-grained dust present on the cometary surface. The obtained results were used to calculate the change in the cometary brightness during its outburst, the upper limit of which was equal to 5.36 magnitude.