38 research outputs found
Acceleration of 1I/`Oumuamua from radiolytically produced H2 in H2O ice
In 2017, 1I/`Oumuamua was identified as the first known interstellar object
in the Solar System. Although typical cometary activity tracers were not
detected, `Oumuamua exhibited a significant non-gravitational acceleration. To
date there is no explanation that can reconcile these constraints. Due to
energetic considerations, outgassing of hyper-volatile molecules is favored
over heavier volatiles like H2O and CO2. However, there are are theoretical
and/or observational inconsistencies with existing models invoking the
sublimation of pure H2 , N2, and CO. Non-outgassing explanations require
fine-tuned formation mechanisms and/or unrealistic progenitor production rates.
Here we report that the acceleration of `Oumuamua is due to the release of
entrapped molecular hydrogen which formed through energetic processing of an
H2O-rich icy body. In this model, `Oumuamua began as an icy planetesimal that
was irradiated at low temperatures by cosmic rays during its interstellar
journey, and experienced warming during its passage through the Solar System.
This explanation is supported by a large body of experimental work showing that
H2 is efficiently and generically produced from H2O ice processing, and that
the entrapped H2 is released over a broad range of temperatures during
annealing of the amorphous water matrix. We show that this mechanism can
explain many of `Oumuamua's peculiar properties without fine-tuning. This
provides further support that `Oumuamua originated as a planetesimal relic
broadly similar to Solar System comets.Comment: Author's version; 23 pages, 3 figure
The Interstellar Interlopers
Interstellar interlopers are bodies formed outside of the solar system but
observed passing through it. The first two identified interlopers, 1I/`Oumuamua
and 2I/Borisov, exhibited unexpectedly different physical properties.
1I/`Oumuamua appeared unresolved and asteroid-like whereas 2I/Borisov was a
more comet-like source of both gas and dust. Both objects moved under the
action of non-gravitational acceleration. These interlopers and their divergent
properties provide our only window so far onto an enormous and previously
unknown galactic population. The number density of such objects is 0.1
AU which, if uniform across the galactic disk, would imply 10 to
10 similar objects in the Milky Way. The interlopers likely formed in,
and were ejected from, the protoplanetary disks of young stars. However, we
currently possess too little data to firmly reject other explanations.Comment: 40 pages, 19 figures, 7 tables, invited review in ARA&A Volume 61,
submitted, comments welcom
Synthetic Detections of Interstellar Objects with The Rubin Observatory Legacy Survey of Space and Time
The discovery of two interstellar objects passing through the Solar System,
1I/`Oumuamua and 2I/Borisov, implies that a galactic population exists with a
spatial number density of order au. The forthcoming Rubin
Observatory Legacy Survey of Space and Time (LSST) has been predicted to detect
more asteroidal interstellar objects like 1I/`Oumuamua. We apply recently
developed methods to simulate a suite of galactic populations of interstellar
objects with a range of assumed kinematics, albedos and size-frequency
distributions (SFD). We incorporate these populations into the objectsInField
(OIF) algorithm, which simulates detections of moving objects by an arbitrary
survey. We find that the LSST should detect between asteroidal
interstellar objects every year (assuming the implied number density), with
sensitive dependence on the SFD slope and characteristic albedo of the host
population. The apparent rate of motion on the sky -- along with the associated
trailing loss -- appears to be the largest barrier to detecting interstellar
objects. Specifically, a relatively large number of synthetic objects would be
detectable by the LSST if not for their rapid sky-motion (
d). Therefore, algorithms that could successfully link and detect
rapidly moving objects would significantly increase the number of interstellar
object discoveries with the LSST (and in general). The mean diameter of
detectable, inactive interstellar objects ranges from m and
depends sensitively on the SFD slope and albedo.Comment: 13 pages, 11 figures, accepted for publication in the Planetary
Science Journa