Exocomets from a Solar System Perspective

Abstract

Exocomets are small bodies releasing gas and dust which orbit stars other than the Sun. Their existence was first inferred from the detection of variable absorption features in stellar spectra in the late 1980s using spectroscopy. More recently, they have been detected through photometric transits from space, and through far-IR/mm gas emission within debris disks. As (exo)comets are considered to contain the most pristine material accessible in stellar systems, they hold the potential to give us information about early stage formation and evolution conditions of extra Solar Systems. In the Solar System, comets carry the physical and chemical memory of the protoplanetary disk environment where they formed, providing relevant information on processes in the primordial solar nebula. The aim of this paper is to compare essential compositional properties between Solar System comets and exocomets. The paper aims to highlight commonalities and to discuss differences which may aid the communication between the involved research communities and perhaps also avoid misconceptions. Exocomets likely vary in their composition depending on their formation environment like Solar System comets do, and since exocomets are not resolved spatially, they pose a challenge when comparing them to high fidelity observations of Solar System comets. Observations of gas around main sequence stars, spectroscopic observations of "polluted" white dwarf atmospheres and spectroscopic observations of transiting exocomets suggest that exocomets may show compositional similarities with Solar System comets. The recent interstellar visitor 2I/Borisov showed gas, dust and nuclear properties similar to that of Solar System comets. This raises the tantalising prospect that observations of interstellar comets may help bridge the fields of exocomet and Solar System comets.

25 pages, 3 figures. To be published in PASP. This paper is the product of a workshop at the Lorentz Centre in Leiden, the Netherlands

References in corpus (56)

• The frequency of planetary debris around young white dwarfs
• Transience of hot dust around sun-like stars
• The Chemical Composition of an Extrasolar Minor Planet
• Spitzer IRS Spectroscopy of IRAS-Discovered Debris Disks
• HST/ACS Multiband Coronagraphic Imaging of the Debris Disk around Beta Pictoris
• Formation of planetary debris discs around white dwarfs I: Tidal disruption of an extremely eccentric asteroid
• Formation of planetary systems by pebble accretion and migration: Growth of gas giants
• A planetesimal orbiting within the debris disc around a white dwarf star
• The Carbon-Rich Gas in the Beta Pictoris Circumstellar Disk
• Carbon Deficiency in Externally-Polluted White Dwarfs: Evidence for Accretion of Asteroids
• Initial characterization of interstellar comet 2I/Borisov
• Detection of exocometary CO within the 440 Myr-old Fomalhaut belt: a similar CO+CO${}_2$ ice abundance in exocomets and Solar System comets
• The Chemical Composition of an Extrasolar Kuiper-Belt-Object
• Water Ice and Dust in the Innermost Coma of Comet 103P/Hartley 2
• The Natural History of 'Oumuamua
• Molecular gas in debris disks around young A-type stars
• Spectral Analysis of the Chandra Comet Survey
• Survival of icy grains in debris discs. The role of photosputtering
• ALMA observations of the $\eta$ Corvi debris disc: inward scattering of CO-rich exocomets by a chain of 3-30 M${}_{\oplus }$ planets?
• Likely Transiting Exocomets Detected by Kepler
• Terrestrial deuterium-to-hydrogen ratio in water in hyperactive comets
• Five steps in the evolution from protoplanetary to debris disk
• Cool DZ white dwarfs I: Identification and spectral analysis
• Kuiper Belt-Like Hot and Cold Populations of Planetesimal Inclinations in the $\beta$ Pictoris Belt Revealed by ALMA
• 2I/Borisov: A C${}_2$ depleted interstellar comet
• Hydrogen delivery onto white dwarfs from remnant exo-Oort cloud comets
• CO mass upper limits in the Fomalhaut ring - the importance of NLTE excitation in debris discs and future prospects with ALMA
• Detection of CN gas in Interstellar Object 2I/Borisov
• Planetesimal driven migration as an explanation for observations of high levels of warm, exozodiacal dust
• Mapping the release of volatiles in the inner comae of comets C/2012 F6 (Lemmon) and C/2012 S1 (ISON) using the Atacama Large Millimeter/Submillimeter Array
• Transiting exocomets detected in broadband light by TESS in the $\beta$ Pictoris system
• Does a Differentiated, Carbonate-Rich, Rocky Object Pollute the White Dwarf SDSSJ104341.53+085558.2?
• Evidence of sub-surface energy storage in comet 67P from the outburst of 2016 July 3
• Implications for planetary system formation from interstellar object 1I/2017 U1 (`Oumuamua)
• 1I/`Oumuamua as a Tidal Disruption Fragment From a Binary Star System
• Complex organic molecules in comets from remote-sensing observations at millimeter wavelengths
• First-light LBT nulling interferometric observations: warm exozodiacal dust resolved within a few AU of eta Corvi
• The Fourth Positive System of Carbon Monoxide in the Hubble Space Telescope Spectra of Comets
• The Evolving Activity of the Dynamically Young Comet C/2009 P1 (Garradd)
• Line Ratios for Solar Wind Charge Exchange with Comets
• Pre-discovery Activity of New Interstellar Comet 2I/Borisov Beyond 5 AU
• Detection of a Water Tracer in Interstellar Comet 2I/Borisov
• Inner mean-motion resonances with eccentric planets: A possible origin for exozodiacal dust clouds
• Could 1I/'Oumuamua be an icy fractal aggregate?
• On the Ubiquity and Stellar Luminosity Dependence of Exocometary CO Gas: Detection around M Dwarf TWA 7
• High resolution optical spectroscopy of the ${\mathrm{N}}_2$-rich comet C/2016 R2 (PanSTARRS)
• Volatile-Rich Circumstellar Gas in the Unusual 49 Ceti Debris Disk
• Changes in the physical environment of the inner coma of 67P/Churyumov-Gerasimenko with decreasing heliocentric distance
• Detection of Diatomic Carbon in 2I/Borisov
• Exocomet signatures around the A-shell star $\Phi$ Leo?
• Molecular Simulations for the Spectroscopic Detection of Atmospheric Gases
• First Detection of Hydrogen in the β Pictoris Gas Disk
• A Dynamical Analysis of the Dust Tail of Comet C/1995 O1 (Hale-Bopp) at High Heliocentric Distances
• Detection of a repeated transit signature in the light curve of the enigma star KIC 8462852: a 928-day period?
• Hot exozodiacal dust: an exocometary origin?
• An unusually large gaseous transit in a debris disc