30 research outputs found
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
Terrestrial Planet Formation Constrained by Mars and the Structure of the Asteroid Belt
Reproducing the large Earth/Mars mass ratio requires a strong mass depletion
in solids within the protoplanetary disk between 1 and 3 AU. The Grand Tack
model invokes a specific migration history of the giant planets to remove most
of the mass initially beyond 1 AU and to dynamically excite the asteroid belt.
However, one could also invoke a steep density gradient created by inward drift
and pile-up of small particles induced by gas-drag, as has been proposed to
explain the formation of close-in super Earths. Here we show that the asteroid
belt's orbital excitation provides a crucial constraint against this scenario
for the Solar System. We performed a series of simulations of terrestrial
planet formation and asteroid belt evolution starting from disks of
planetesimals and planetary embryos with various radial density gradients and
including Jupiter and Saturn on nearly circular and coplanar orbits. Disks with
shallow density gradients reproduce the dynamical excitation of the asteroid
belt by gravitational self-stirring but form Mars analogs significantly more
massive than the real planet. In contrast, a disk with a surface density
gradient proportional to reproduces the Earth/Mars mass ratio but
leaves the asteroid belt in a dynamical state that is far colder than the real
belt. We conclude that no disk profile can simultaneously explain the structure
of the terrestrial planets and asteroid belt. The asteroid belt must have been
depleted and dynamically excited by a different mechanism such as, for
instance, in the Grand Tack scenario.Comment: Accepted for publication in MNRA
Assessing the spin-orbit obliquity of low-mass planets in the breaking the chain formation model: A story of misalignment
The spin-orbit obliquity of a planetary system constraints its formation
history. A large obliquity may either indicate a primordial misalignment
between the star and its gaseous disk or reflect the effect of different
mechanisms tilting planetary systems after formation. Observations and
statistical analysis suggest that system of planets with sizes between 1 and 4
R have a wide range of obliquities (), and that
single- and multi-planet transiting have statistically indistinguishable
obliquity distributions. Here, we revisit the ``breaking the chains'' formation
model with focus in understanding the origin of spin-orbit obliquities. This
model suggests that super-Earths and mini-Neptunes migrate close to their host
stars via planet-disk gravitational interactions, forming chain of planets
locked in mean-motion resonances. After gas-disk dispersal, about 90-99\% of
these planetary systems experience dynamical instabilities, which spread the
systems out. Using synthetic transit observations, we show that if planets are
born in disks where the disk angular momentum is virtually aligned with the
star's rotation spin, their final obliquity distributions peak at about 5
degrees or less, and the obliquity distributions of single and multi-planet
transiting systems are statistically distinct. By treating the star-disk
alignment as a free-parameter, we show that the obliquity distributions of
single and multi-planet transiting systems only become statistically
indistinguishable if planets are assumed to form in primordially misaligned
natal disks with a ``tilt'' distribution peaking at 10-20 deg. We
discuss the origin of these misalignments in the context of star formation and
potential implications of this scenario for formation models.Comment: 11 pages, 9 figures, 2 tables. Accepted for publication in MNRA
Low Thrust Propelled Close Approach Maneuvers
The study of orbital maneuvers in space missions is a very important problem in astrodynamics. One of the options is the use of a “gravity assisted” maneuver, which is a technique where a spacecraft passes close to a celestial body and uses the gravity of this body to change its trajectory. This approach trajectory has symmetry with respect to the periapsis line when observed from a reference frame fixed in the approached body. There is also a more complex maneuver, when the passage by the celestial body is combined with the application of propulsion, either to give extra energy to the spacecraft or to help to satisfy other constraints required by the mission, like passing by a giving point or region in space. The main object of this study is to measure the efficiency of the application of a continuous thrust combined with the “gravity assisted” maneuver. The effect of this combination is analyzed using maps that give the energy variation of the spacecraft as function of the parameters related to the maneuver. This analysis is made from the point of view of the variation of energy of the spacecraft with respect to the main body of the system. The continuous thrust is applied in the different regions of the trajectory to evaluate the effects of the locations of the thrusting arcs in the variations of energy. The effects of the variations of the direction of the thrust are also studied. This type of combined maneuver may be used to give extra energy to the spacecraft and keeping control of the trajectory during the close approach to better position the spacecraft to complete the mission
Results on stellar occultations by (307261) 2002 MS4
Transneptunian Objects (TNOs) are the remnants of our planetary system and can retain information about the early stages of the Solar System formation. Stellar occultation is a groundbased method used to study these distant bodies which have been presenting exciting results mainly about their physical properties. The big TNO called 2002 MS4 was discovered by Trujillo, C. A., & Brown, M. E., in 2002 using observations made at the Palomar Observatory (EUA). It is classified as a hot classical TNO, with orbital parameters a = 42 AU, e = 0.139, and i = 17.7º. Using thermal measurements with PACS (Herschel) and MIPS (Spitzer Space Telescope) instruments, Vilenius et al. 2012 obtained a radius of 467 +/- 23.5 km and an albedo of 0.051.Predictions of stellar occultations by this body in 2019 were obtained using the Gaia DR2 catalogue and NIMA ephemeris (Desmars et al. 2015) and made available in the Lucky Star web page (https://lesia.obspm.fr/lucky-star/). Four events were observed in South America and Canada. The first stellar occultation was detected on 09 July 2019, resulting in two positives and four negatives chords, including a close one which proven to be helpful to constrain the body’s size. This detection also allowed us to obtain a precise astrometric position that was used to update its ephemeris and improve the predictions of the following events. Two of them were detected on 26 July 2019, separated by eight hours. The first event was observed from South America and resulted in three positive detections, while the second, observed from Canada, resulted in a single chord. Another double chord event was observed on 19 August 2019 also from Canada.Facultad de Ciencias Astronómicas y Geofísica
The stability evolution of a family of simply periodic lunar orbits
The present work deals with a family of simply periodic orbits around the Moon in the rotating Earth Moon-particle system. Taking the framework of the planar, circular, restricted three-body problem, we follow the evolution of this family of periodic orbits using the numerical technique of Poincaré surface of section. The maximum amplitude of oscillation about the periodic orbits are determined and can be used as a parameter to measure the degree of stability in the phase space for such orbits. Despite the fact that the whole family of periodic orbits remain stable, there is a dichotomy in the quasi-periodic ones at the Jacobi constant Cj = 2.85. The quasi-periodic orbits with Cj 2.85. © 1999 Elsevier Science Ltd. All rights reserved
An unaccounted component on the Prometheus and Pandora offset angular positions
Near the turning of this millennium (1996–2004) it was detected that Prometheus and Pandora were not in their angular positions as predicted from their discoveries by the Voyager spacecrafts (1980). This is known as the problem of the lags of Prometheus and Pandora. The explanation for the origin of these lags is the chaotic motion associated with 121:118 mean motion resonance between the satellites. In the present work we revisit this problem and adopting the most extensive set of lags data, given by [R.G. French et al., Icarus 162, 143 (2003)], to show the need of unaccounted effects to produce the measured lags. By the analysis of conservation of angular momentum it can be verified that the mutual interaction between Prometheus and Pandora should be inversely proportional to the ratio of their masses. In this way, only the gravitational interaction between the two satellites does not explain such values. Consequently, the ratio between the lags of Prometheus and Pandora, , should be constant, and approximately the value of the inverse ratio between their masses (0.56, from [R.G. French et al., Icarus 162, 143 (2003)]). However, the values of from the measured lags are much higher, ranging from 48% up to 68% larger. Beyond that, the values increase over time in a rate given by the equation (t = 0.067 + 0.013t). Therefore, this analysis clearly shows the need of other mechanisms beyond the mutual interaction between Prometheus and Pandora in order to produce such values of lags. We estimate that at least one effect that produces an additional variation of mean motion of about 0.45°/year in one of the satellites for about 20 years would be necessary
Formation of the Janus-Epimetheus system through collisions
Context. Co-orbital systems are bodies that share the same mean orbit.
They can be divided into different families according to the relative mass of the
co-orbital partners and the particularities of their movement. Janus and Epimetheus are
unique in that they are the only known co-orbital pair of comparable masses and thus the
only known system in mutual horseshoe orbit.
Aims. We aim to establish whether the Janus-Epimetheus system might have
formed by disruption of an object in the current orbit of Epimetheus.
Methods. We assumed that four large main fragments were formed and
neglected smaller fragments. We used numerical integration of the full N-body problem to study the
evolution of different fragment arrangements. Collisions were assumed to result in
perfectly inelastic merging of bodies. We statistically analysed the outcome of these
simulations to infer whether co-orbital systems might have formed from the chosen initial
conditions.
Results. Depending on the range of initial conditions, up to
9% of the simulations evolve
into co-orbital systems. Initial velocities around the escape velocity of Janus yield the
highest formation probability. Analysis of the evolution shows that all co-orbital systems
are produced via secondary collisions. The velocity of these collisions needs to be low
enough that the fragments can merge and not be destroyed. Generally, collisions are found
to be faster than an approximate cut-off velocity threshold. However, given a sufficiently
low initial velocity, up to 15% of collisions is expected to result in merging. Hence, the
results of this study show that the considered formation scenario is viable