1,028 research outputs found
Characterizing the original ejection velocity field of the Koronis family
An asteroid family forms as a result of a collision between an impactor and a
parent body. The fragments with ejection speeds higher than the escape velocity
from the parent body can escape its gravitational pull. The cloud of escaping
debris can be identified by the proximity of orbits in proper element, or
frequency, domains. Obtaining estimates of the original ejection speed can
provide valuable constraints on the physical processes occurring during
collision, and used to calibrate impact simulations. Unfortunately, proper
elements of asteroids families are modified by gravitational and
non-gravitational effects, such as resonant dynamics, encounters with massive
bodies, and the Yarkovsky effect, such that information on the original
ejection speeds is often lost, especially for older, more evolved families.
It has been recently suggested that the distribution in proper inclination of
the Koronis family may have not been significantly perturbed by local dynamics,
and that information on the component of the ejection velocity that is
perpendicular to the orbital plane (), may still be available, at least in
part. In this work we estimate the magnitude of the original ejection velocity
speeds of Koronis members using the observed distribution in proper
eccentricity and inclination, and accounting for the spread caused by dynamical
effects. Our results show that i) the spread in the original ejection speeds
is, to within a 15% error, inversely proportional to the fragment size, and ii)
the minimum ejection velocity is of the order of 50 m/s, with larger values
possible depending on the orbital configuration at the break-up.Comment: 18 pages, 10 figures, 4 tables. Accepted for publication in Icaru
Identification and Dynamical Properties of Asteroid Families
Asteroids formed in a dynamically quiescent disk but their orbits became
gravitationally stirred enough by Jupiter to lead to high-speed collisions. As
a result, many dozen large asteroids have been disrupted by impacts over the
age of the Solar System, producing groups of fragments known as asteroid
families. Here we explain how the asteroid families are identified, review
their current inventory, and discuss how they can be used to get insights into
long-term dynamics of main belt asteroids. Electronic tables of the membership
for 122 notable families are reported on the Planetary Data System node.Comment: Asteroids IV chapte
On the Erigone family and the secular resonance
The Erigone family is a C-type group in the inner main belt. Its age has been
estimated by several researchers to be less then 300 My, so it is a relatively
young cluster. Yarko-YORP Monte Carlo methods to study the chronology of the
Erigone family confirm results obtained by other groups. The Erigone family,
however, is also characterized by its interaction with the secular
resonance. While less than 15% of its members are currently in librating states
of this resonance, the number of objects, members of the dynamical group, in
resonant states is high enough to allow to use the study of dynamics inside the
resonance to set constraints on the family age.
Like the and secular resonances, the resonance is
characterized by one stable equilibrium point at in the
resonance plane , where is the
resonant angle of the resonance. Diffusion in this plane occurs on
timescales of My, which sets a lower limit on the Erigone family
age. Finally, the minimum time needed to reach a steady-state population of
librators is about 90 My, which allows to impose another, independent
constraint on the group age.Comment: This paper has 11 pages, 12 figures, and 1 table. Accepted for
publication in MNRA
Footprints of a possible Ceres asteroid paleo-family
Ceres is the largest and most massive body in the asteroid main belt.
Observational data from the Dawn spacecraft reveal the presence of at least two
impact craters about 280~km in diameter on the Ceres surface, that could have
expelled a significant number of fragments. Yet, standard techniques for
identifying dynamical asteroid families have not detected any Ceres family. In
this work, we argue that linear secular resonances with Ceres deplete the
population of objects near Ceres. Also, because of the high escape velocity
from Ceres, family members are expected to be very dispersed, with a
considerable fraction of km-sized fragments that should be able to reach the
pristine region of the main belt, the area between the 5J:-2A and 7J:-3A
mean-motion resonances, where the observed number of asteroids is low. Rather
than looking for possible Ceres family members near Ceres, here we propose to
search in the pristine region. We identified 156 asteroids whose taxonomy,
colors, albedo could be compatible with being fragments from Ceres. Remarkably,
most of these objects have inclinations near that of Ceres itself.Comment: 12 pages, 6 figures, 1 table. Accepted for publication in MNRA
Dynamical evolution of V-type photometric candidates in the outer Main-belt
V-type asteroids, characterized by two absorption bands at 1.0 and 2.0 , are usually thought to be portions of the crust of differentiated or
partially differentiated bodies. Most V-type asteroids are found in the inner
main belt and are thought to be current or past members of the Vesta dynamical
family. Recently, several V-type photometric candidates have been identified in
the central and outer main belt.
While the dynamical evolution of V-type photometric candidates in the central
main belt has been recently investigated, less attention has been given to the
orbital evolution of basaltic material in the outer main belt as a whole. Here
we identify known and new V-type photometric candidates in this region, and
study their orbital evolution under the effect of gravitational and
non-gravitational forces. A scenario in which a minimum of three local sources,
possibly associated with the parent bodies of (349) Dembowska, (221) Eos, and
(1459) Magnya, could in principle explain the current orbital distribution of
V-type photometric candidates in the region.Comment: This paper has 6 figures and 1 table. Accepted for publication in
MNRAS. arXiv admin note: text overlap with arXiv:1401.633
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