Is Interstellar Object 2I/Borisov a Stardust Comet? Predictions for the Post Perihelion Period

• Main Author: Eubanks, T. Marshall
• Format: Journal Article
• Language: English
• Published: 29-12-2019
• Subjects: Physics - Earth and Planetary Astrophysics; Physics - Solar and Stellar Astrophysics
• DOI: 10.48550/arxiv.1912.12730

The detection of interstellar bodies passing near the Sun offers the
opportunity to observe not just objects similar to those in the solar system,
but also unfamiliar objects without solar system analogues. Here I show that
Asymptotic Giant Branch (AGB) stellar evolution may lead to the creation, out
of stardust, of substantial numbers of nomadic Post-Main-Sequence Objects
(PMSOs). ABG nucleosynthesis will produce three broad classes of PMSO
chemistry, oxygen, carbon and nitrogen rich (O-rich, C-rich, N-rich,
respectively), depending largely on the original stellar mass. I further show
that the Interstellar Comet 2I/Borisov (2I) belongs to a kinematic dynamical
stream, the Wolf 630 stream, with an age and galactic orbit consistent with its
origination as a stardust comet; the apparent lack of water in the 2I coma is
consistent with it being a C-rich PMSO. I also provide predictions for
distinguishing stardust comets from more conventional interstellar comets and
asteroids ejected during planetary formation; these can be applied to 2I in its
upcoming observational phase in early 2020 as it moves away from the Sun. In
particular, isotope ratios of the CNO elements could be dispositive, IR
detection of the 11.3 {\mu}m SiC line, the 30 {\mu}m line, or the IR PAH lines
would provide strong evidence for a C-rich PMSO and detection of Na or Li
enhancement would indicate an N-rich PMSO.