Comet 12P/Pons-Brooks: Dust properties

Abstract

Comet 12P/Pons-Brooks, a Halley-type comet with a 71-year orbital period, was first discovered in 1812. It follows a highly inclined trajectory, originating from just beyond Neptune’s orbit. Ground-based observations have shown that the comet exhibited activity at a heliocentric distance of 11 au during its approach to the Sun. Numerous studies have since focused on its behavior, particularly its pre-perihelion outbursts, which have provided valuable insights into its dynamic and volatile nature.

This study examines the dust behavior of 12P following its perihelion passage. Using the 0.6 m Helen Sawyer Hogg telescope at the Complejo Astronómico El Leoncito (CASLEO), a series of images were captured between May and June 2024 using broadband I, R, and V filters. Morphological, photometric, and numerical analyses were performed to investigate the comet’s dust characteristics. Enhanced imaging revealed two active regions within an isotropic coma, which contributed to its distinctive “devil comet” appearance. Photometric analysis, based on the magnitudes and dust production rate from the $A(0°)f\rho$ parameter, indicated ordinary dust behavior, with no characteristic outbursts observed.

To gain further insights into 12P’s dust behavior, the data were fitted to a new theoretical model for studying dust in comets. This model suggests that the dust coma primarily consisted of large particles emitted from two high-latitude active areas at a velocity of approximately $409{\text{ms}}^{-1}$, assuming a rotation period of 57 h.