Col-OSSOS: Colors of the Interstellar Planetesimal 1I/2017 U1

    Research output: Contribution to journalArticle

    Early online date

    View graph of relations

    The recent discovery by Pan-STARRS1 of 1I/2017 U1 (`Oumuamua), on an unbound and hyperbolic orbit, offers a rare opportunity to explore the planetary formation processes of other stars, and the effect of the interstellar environment on a planetesimal surface. 1I/`Oumuamua's close encounter with the inner Solar System in 2017 October was a unique chance to make observations matching those used to characterize the small-body populations of our own Solar System. We present near-simultaneous g$^\prime$, r$^\prime$, and J photometry and colors of 1I/`Oumuamua from the 8.1-m Frederick C. Gillett Gemini North Telescope, and $gri$ photometry from the 4.2 m William Herschel Telescope. Our g$^\prime$r$^\prime$J observations are directly comparable to those from the high-precision \textit{Colours of the Outer Solar System Origins Survey} (Col-OSSOS), and offer unique diagnostic information for distinguishing between outer Solar System surfaces. Substantial, correlated near-infrared and optical variability is present, with the same trend in both near-infrared and optical. Our observations confirm that 1I/`Oumuamua rotates with a double-peaked period of $8.10 \pm 0.42$ hours and is a highly elongated body with an axial ratio of at least 5.3:1, implying that it has significant internal cohesion. 1I/`Oumuamua's color is at the neutral end of the range of observed $g-r$ and $r-J$ solar-reflectance colors, relative to asteroids, more distant minor planets, and to the trans-Neptunian populations measured by Col-OSSOS. The color of the first interstellar planetesimal is like the colors of the Solar System, in particular some of the dynamically excited objects of the Kuiper belt and the less-red Jupiter Trojans.


    • Col-OSSOS: Colors of the Interstellar Planetesimal 1I/‘Oumuamua

      Rights statement: © 2017. The American Astronomical Society. All rights reserved. This work is made available online in accordance with the publisher’s policies. Please refer to any applicable terms of use of the publisher.

      Final published version, 899 KB, PDF-document


    Original languageEnglish
    Pages (from-to)1-7
    JournalThe Astrophysical Journal. Letters
    Journal publication date18 Dec 2017
    Early online date18 Dec 2017
    StateEarly online date - 18 Dec 2017

      Research areas

    • Astrophysics - Earth and Planetary Astrophysics

    ID: 139360806