Abstract
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.
Original language | English |
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Pages (from-to) | 1-7 |
Journal | The Astrophysical Journal Letters |
Volume | 851 |
Early online date | 18 Dec 2017 |
DOIs | |
Publication status | Published - 2017 |
Keywords
- Astrophysics - Earth and Planetary Astrophysics