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

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    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.

    Documents

    • 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.

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    DOI

    Original languageEnglish
    Pages (from-to)1-7
    JournalThe Astrophysical Journal. Letters
    Journal publication date18 Dec 2017
    Volume851
    Early online date18 Dec 2017
    DOIs
    StateEarly online date - 18 Dec 2017

      Research areas

    • Astrophysics - Earth and Planetary Astrophysics

    ID: 139360806