Tidal fragmentation as the origin of 1I/2017 U1 (‘Oumuamua). (arXiv:2004.07218v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_Y/0/1/0/all/0/1">Yun Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lin_D/0/1/0/all/0/1">Douglas N. C. Lin</a>
The first discovered interstellar object (ISO), `Oumuamua (1I/2017 U1) shows
a dry and rocky surface, an unusually elongated short-to-long axis ratio $c/a
lesssim 1/6$, a low velocity relative to the local standard of rest ($sim 10$
km s$^{-1}$), non-gravitational accelerations, and tumbles on a few hours
timescale. The inferred number density ($sim 3.5 times 10^{13} – 2 times
10^{15}$ pc$^{-3}$) for a population of asteroidal ISOs outnumbers cometary
ISOs by $geq 10^3$, in contrast to the much lower ratio ($lesssim 10^{-2}$)
of rocky/icy Kuiper belt objects. Although some scenarios can cause the
ejection of asteroidal ISOs, a unified formation theory has yet to
comprehensively link all `Oumuamua’s puzzling characteristics and to account
for the population. Here we show by numerical simulations that `Oumuamua-like
ISOs can be prolifically produced through extensive tidal fragmentation and
ejected during close encounters of their volatile-rich parent bodies with their
host stars. Material strength enhanced by the intensive heating during
periastron passages enables the emergence of extremely elongated triaxial ISOs
with shape $c/a lesssim 1/10$, sizes $a sim 100$ m, and rocky surfaces.
Although volatiles with low sublimation temperature (such as CO) are
concurrently depleted, H$_2$O buried under surfaces is preserved in these ISOs,
providing an outgassing source without measurable cometary activities for
`Oumuamua’s non-gravitational accelerations during its passage through the
inner Solar System. We infer that the progenitors of `Oumuamua-like ISOs may be
km-sized long-period comets from Oort clouds, km-sized residual planetesimals
from debris disks, or planet-size bodies at a few AU, orbiting around low-mass
main-sequence stars or white dwarfs. These provide abundant reservoirs to
account for `Oumuamua’s occurrence rate.
The first discovered interstellar object (ISO), `Oumuamua (1I/2017 U1) shows
a dry and rocky surface, an unusually elongated short-to-long axis ratio $c/a
lesssim 1/6$, a low velocity relative to the local standard of rest ($sim 10$
km s$^{-1}$), non-gravitational accelerations, and tumbles on a few hours
timescale. The inferred number density ($sim 3.5 times 10^{13} – 2 times
10^{15}$ pc$^{-3}$) for a population of asteroidal ISOs outnumbers cometary
ISOs by $geq 10^3$, in contrast to the much lower ratio ($lesssim 10^{-2}$)
of rocky/icy Kuiper belt objects. Although some scenarios can cause the
ejection of asteroidal ISOs, a unified formation theory has yet to
comprehensively link all `Oumuamua’s puzzling characteristics and to account
for the population. Here we show by numerical simulations that `Oumuamua-like
ISOs can be prolifically produced through extensive tidal fragmentation and
ejected during close encounters of their volatile-rich parent bodies with their
host stars. Material strength enhanced by the intensive heating during
periastron passages enables the emergence of extremely elongated triaxial ISOs
with shape $c/a lesssim 1/10$, sizes $a sim 100$ m, and rocky surfaces.
Although volatiles with low sublimation temperature (such as CO) are
concurrently depleted, H$_2$O buried under surfaces is preserved in these ISOs,
providing an outgassing source without measurable cometary activities for
`Oumuamua’s non-gravitational accelerations during its passage through the
inner Solar System. We infer that the progenitors of `Oumuamua-like ISOs may be
km-sized long-period comets from Oort clouds, km-sized residual planetesimals
from debris disks, or planet-size bodies at a few AU, orbiting around low-mass
main-sequence stars or white dwarfs. These provide abundant reservoirs to
account for `Oumuamua’s occurrence rate.
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