Exocomets from a solar system perspective

Paul A. Strøm*, Dennis Bodewits, Matthew M. Knight, Flavien Kiefer, Geraint H. Jones, Quentin Kral, Luca Matrà, Eva Bodman, Maria Teresa Capria, Ilsedore Cleeves, Alan Fitzsimmons, Nader Haghighipour, John H.D. Harrison, Daniela Iglesias, Mihkel Kama, Harold Linnartz, Liton Majumdar, Ernst J.W. de Mooij, Stefanie N. Milam, Cyrielle OpitomIsabel Rebollido, Laura K. Rogers, Colin Snodgrass, Clara Sousa-Silva, Siyi Xu, Zhong Yi Lin, Sebastian Zieba

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)
143 Downloads (Pure)


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 to allow for the development of new observational methods and techniques. 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. The compositional properties of solar system comets and exocomets are summarized before providing an observational comparison between them. 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.

Original languageEnglish
Article number101001
Pages (from-to)1-19
Number of pages19
JournalPublications of the Astronomical Society of the Pacific
Issue number1016
Publication statusPublished - 16 Sept 2020


  • Comets
  • Kuiper belt
  • Main-belt comets
  • Photometry
  • Small solar system bodies
  • Spectroscopy

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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