Mid-infrared observations of the nucleus of Comet P/2016 BA14 (PANSTARRS)

We present mid-infrared observations of comet P/2016 BA(14) (PANSTARRS), which were obtained on UT 2016 March 21.3 at heliocentric and geocentric distances of 1.012 au and 0.026 au, respectively, approximately 30 h before its closest approach to Earth (0.024 au) on UT 2016 March 22.6. Low-resolution (lambda Delta lambda similar to 250) spectroscopic observations in the N-band and imaging observations with four narrow-band filters (centered at 8.8, 12.4, 17.7 and 18.8 mu m) in the N- and Q-bands were obtained using the Cooled Mid-Infrared Camera and Spectrometer (COMICS) mounted on the 8.2-m Subaru telescope atop Maunakea, Hawaii. The observed spatial profiles of P/2016 BA(14) at different wavelengths are consistent with a point-spread function. Owing to the close approach of the comet to the Earth, the observed thermal emission from the comet is dominated by the thermal emission from its nucleus rather than its dust coma. The observed spectral energy distribution of the nucleus at mid-infrared wavelengths is consistent with a Planck function at temperature T similar to 350 K, with the effective diameter of P/2016 BA(14) estimated as similar to 0.8 km (by assuming an emissivity of 0.97). The normalized emissivity spectrum of the comet exhibits absorption-like features that are not reproduced by the anhydrous minerals typically found in cometary dust coma, such as olivine and pyroxene. Instead, the spectral features suggest the presence of large grains of phyllosilicate minerals and organic materials. Thus, our observations indicate that an inactive small body covered with these processed materials is a possible end state of comets.

Automated summary

The mid-infrared observations of comet P/2016 BA(14) reveal a nucleus temperature of around 350K and an estimated diameter of 0.8 km, indicating the presence of mineral and organic materials on the surface, suggesting that an inactive small body covered with these materials may be a possible end state of comets.