اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدDiscovery of a young asteroid cluster associated with P/2012~F5 (Gibbs)
195
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We present the results of our search for a dynamical family around the active asteroid P/2012F5 (Gibbs). By applying the hierarchical clustering method, we discover an extremely compact 9-body cluster associated with P/2012F5. The statistical significance of this newly discovered Gibbs cluster is estimated to be >99.9%, strongly suggesting that its members share a common origin. The cluster is located in a dynamically cold region of the outer main-belt at a proper semi-major axis of about 3.005 AU, and all members are found to be dynamically stable over very long time-scales. Backward numerical orbital integrations show that the age of the cluster is only 1.5 $pm$ 0.1 Myr. Taxonomic classifications are unavailable for most of the cluster members, but SDSS spectrophotometry available for two cluster members indicate that both appear to be $Q$-type objects. We also estimate a lower limit of the size of the parent body to be about 10 km, and find that the impact event which produced the Gibbs cluster is intermediate between a cratering and a catastrophic collision. In addition, we search for new main-belt comets in the region of the Gibbs cluster by observing seven asteroids either belonging to the cluster, or being very close in the space of orbital proper elements. However, we do not detect any convincing evidence of the presence of a tail or coma in any our targets. Finally, we obtain optical images of P/2012F5, and find absolute R-band and V-band magnitudes of $H_R$ = 17.0 $pm$ 0.1 mag and $H_V$ = 17.4 $pm$ 0.1 mag, respectively, corresponding to an upper limit on the diameter of the P/2012F5 nucleus of about 2 km.
قيم البحث
اقرأ أيضاً
The dust emission from active asteroids is likely driven by collisions, fast rotation, sublimation of embedded ice, and combinations of these. Characterising these processes leads to a better understanding of their respective influence on the evoluti
on of the asteroid population. We study the role of fast rotation in the active asteroid 358P (P 2012/T1). We obtained two nights of deep imaging of 358P with SOAR/Goodman and VLT/FORS2. We derived the rotational light curve from time-resolved photometry and searched for large fragments and debris > 8 mm in a stacked, ultra-deep image. The nucleus has an absolute magnitude of m_R=19.68, corresponding to a diameter of 530 m for standard assumptions on the albedo and phase function of a C-type asteroid. We do not detect fragments or debris that would require fast rotation to reduce surface gravity to facilitate their escape. The 10-hour light curve does not show an unambiguous periodicity.
In this note we have shown that a newly discovered comet P/2017 S5 (ATLAS), that moves around the Sun in an asteroid-like orbit, is a member of the Theobalda asteroid family.
Asteroid 2012 TC4 is a small ($sim$10 m) near-Earth object that was observed during its Earth close approaches in 2012 and 2017. Earlier analyses of light curves revealed its excited rotation state. We collected all available photometric data from th
e two apparitions to reconstruct its rotation state and convex shape model. We show that light curves from 2012 and 2017 cannot be fitted with a single set of model parameters -- the rotation and precession periods are significantly different for these two data sets and they must have changed between or during the two apparitions. Nevertheless, we could fit all light curves with a dynamically self-consistent model assuming that the spin states of 2012 TC4 in 2012 and 2017 were different. To interpret our results, we developed a numerical model of its spin evolution in which we included two potentially relevant perturbations: (i) gravitational torque due to the Sun and Earth, and (ii) radiation torque known as the Yarkovsky-OKeefe-Radzievskii-Paddack (YORP) effect. Despite our model simplicity, we found that the role of gravitational torques is negligible. Instead, we argue that the observed change of its spin state may be plausibly explained as a result of the YORP torque. To strengthen this interpretation we verify that (i) the internal energy dissipation due to material inelasticity, and (ii) an impact with a sufficiently large interplanetary particle are both highly unlikely causes its observed spin state change. If true, this is the first case when the YORP effect has been detected for a tumbling body.
Only a few hot Jupiters are known to orbit around fast rotating stars. These exoplanets are harder to detect and characterize and may be less common than around slow rotators. Here, we report the discovery of the transiting hot Jupiter XO-6b, which o
rbits a bright, hot, and fast rotating star: V = 10.25, Teff = 6720 +/- 100 K, v sin i = 48 +/- 3 km/s. We detected the planet from its transits using the XO instruments and conducted a follow-up campaign. Because of the fast stellar rotation, radial velocities taken along the orbit do not yield the planets mass with a high confidence level, but we secure a 3-sigma upper limit Mp < 4.4 MJup. We also obtain high resolution spectroscopic observations of the transit with the SOPHIE spectrograph at the 193-cm telescope of the Observatoire de Haute-Provence and analyze the stellar lines profile by Doppler tomography. The transit is clearly detected in the spectra. The radii measured independently from the tomographic analysis and from the photometric lightcurves are consistent, showing that the object detected by both methods is the same and indeed transits in front of XO-6. We find that XO-6b lies on a prograde and misaligned orbit with a sky-projected obliquity lambda = -20.7 +/- 2.3 deg. The rotation period of the star is shorter than the orbital period of the planet: Prot < 2.12 days, Porb = 3.77 days. Thus, this system stands in a largely unexplored regime of dynamical interactions between close-in giant planets and their host stars.
Asteroid families are groups of minor planets that have a common origin in breakup events. The very young compact asteroid clusters are the natural laboratory to study resonance related chaotic and nonlinear dynamics. The present dynamical configurat
ions and evolution of asteroid associations strongly depends on their ages. In present paper we allocate subclass of very young asteroid families (younger than 1 Myr). We show that resonance-related chaos can play a very important role in dynamics of very young asteroid families. In case of Datura family chaos may be explained by high order mean motion resonance 9:16 with Mars. In case Hobson family chaos is affected by secular resonance. In other considered cases (Kapbos cluster and Lucascavin cluster) origin of chaotic behavior is still unknown. The effect of resonance is very selective in all cases: we see very stable orbits in the vicinity of chaotic ones. In the high order resonance transfer from initial to final orbit take place by temporary capture in exact resonance. The large asteroids (Ceres, Vesta) can made significant effect on dynamic of small bodies in resonance. In some cases (as for Datura and Lucascavin family), their perturbations can extend area of chaotic motion.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
