Implications for Planetary System Formation from Interstellar Object 1I/2017 U1 ('Oumuamua)

David E. Trilling, Tyler Robinson, Alissa Roegge, Colin Orion Chandler, Nathan Smith, Mark Loeffler, Chad Trujillo, Samuel Navarro-Meza, Lori M. Glaspie

Research output: Contribution to journalArticlepeer-review

54 Scopus citations


The recently discovered minor body 1I/2017 U1 ('Oumuamua) is the first known object in our solar system that is not bound by the Sun's gravity. Its hyperbolic orbit (eccentricity greater than unity) strongly suggests that it originated outside our solar system; its red color is consistent with substantial space weathering experienced over a long interstellar journey. We carry out a simple calculation of the probability of detecting such an object. We find that the observed detection rate of 1I-like objects can be satisfied if the average mass of ejected material from nearby stars during the process of planetary formation is ∼20 Earth masses, similar to the expected value for our solar system. The current detection rate of such interstellar interlopers is estimated to be 0.2 yr-1, and the expected number of detections over the past few years is almost exactly one. When the Large Synoptic Survey Telescope begins its wide, fast, deep all-sky survey, the detection rate will increase to 1 yr-1. Those expected detections will provide further constraints on nearby planetary system formation through a better estimate of the number and properties of interstellar objects.

Original languageEnglish (US)
Article numberL38
JournalAstrophysical Journal Letters
Issue number2
StatePublished - Dec 1 2017


  • comets: individual (1I/2017 U1 ('Oumuamua))
  • local interstellar matter
  • minor planets, asteroids: individual (1I/2017 U1 ('Oumuamua))
  • planetary systems
  • protoplanetary disks
  • solar neighborhood

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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