177 research outputs found
Primordial Orbital Alignment of Sednoids
We examined the past history of the three most detached TransNeptunian
Objects (TNOs) -- Sedna, 2012 VP113, and Leleakuhonua (2015 TG387) -- the three
clearest members of the dynamical class known as sednoids, with high perihelia
distances . By integrating backward their nominal (and a set of cloned)
orbits for the Solar System's age, we surprisingly find that the only time all
their apsidal lines tightly cluster was 4.5 Gyr ago, at perihelion longitude
of 200{\deg}. This "primordial alignment" is independent of the
observational biases that contribute to the current on-sky clustering in the
large-semimajor axis Kuiper Belt. If future sednoid discoveries confirm these
findings, this strongly argues for an initial event during the planet formation
epoch which imprinted this particular apsidal orientation on the early detached
TNO population and then subsequently modified only by the simple precession
from the 4 giant planets. If other sednoids also cluster around the same
primordial value, various models suggesting a still present planet in the outer
Solar System would be incompatible with this alignment. We inspected two
scenarios that could potentially explain the primordial alignment. First, a
rogue planet model (where another massive planet raises perihelia near its own
longitude until ejection) naturally produces this signature. Alternatively, a
close stellar passage early in Solar System history raises perihelia, but it is
poor at creating strong apsidal clustering. We show that all other known
au TNOs are either too perturbed or orbits are still too uncertain to
provide evidence for or against this paradigm.Comment: 9 pages, 4 figures, submitted to ApJ
Pencil-Beam Surveys for Faint Trans-Neptunian Objects
We have conducted pencil-beam searches for outer solar system objects to a
limiting magnitude of R ~ 26. Five new trans-neptunian objects were detected in
these searches. Our combined data set provides an estimate of ~90
trans-neptunian objects per square degree brighter than ~ 25.9. This estimate
is a factor of 3 above the expected number of objects based on an extrapolation
of previous surveys with brighter limits, and appears consistent with the
hypothesis of a single power-law luminosity function for the entire
trans-neptunian region. Maximum likelihood fits to all self-consistent
published surveys with published efficiency functions predicts a cumulative sky
density Sigma(<R) obeying log10(Sigma) = 0.76(R-23.4) objects per square degree
brighter than a given magnitude R.Comment: Accepted by AJ, 18 pages, including 6 figure
Constraints on the Orbital Evolution of Triton
We present simulations of Triton's post-capture orbit that confirm the
importance of Kozai-type oscillations in its orbital elements. In the context
of the tidal orbital evolution model, these variations require average
pericenter distances much higher than previously published, and the timescale
for the tidal orbital evolution of Triton becomes longer than the age of the
Solar System. Recently-discovered irregular satellites present a new constraint
on Triton's orbital history. Our numerical integrations of test particles
indicate a timescale for Triton's orbital evolution to be less than yrs
for a reasonable number of distant satellites to survive Triton's passage. This
timescale is inconsistent with the exclusively tidal evolution (time scale of
yrs), but consistent with the interestion with the debris from
satellite-satellite collisions. Any major regular satellites will quickly
collide among themselves after being perturbed by Triton, and the resulting
debris disk would eventually be swept up by Triton; given that the total mass
of the Uranian satellite system is 40% of that of Triton, large scale evolution
is possible. This scenario could have followed either collisional or the
recently-discussed three-body-interaction-based capture.Comment: 10 pages, 4 figures, accepted for ApJ
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