21 research outputs found
Collision probabilities of migrating small bodies and dust particles with planets
Probabilities of collisions of migrating small bodies and dust particles
produced by these bodies with planets were studied. Various Jupiter-family
comets, Halley-type comets, long-period comets, trans-Neptunian objects, and
asteroids were considered. The total probability of collisions of any
considered body or particle with all planets did not exceed 0.2. The amount of
water delivered from outside of Jupiter's orbit to the Earth during the
formation of the giant planets could exceed the amount of water in Earth's
oceans. The ratio of the mass of water delivered to a planet by Jupiter-family
comets or Halley-type comets to the mass of the planet can be greater for Mars,
Venus, and Mercury, than that for Earth.Comment: 7 pages (original paper consists of 4 pages, with all sub-figures on
one page). Proceedings of the IAU Symposium 263 "Icy bodies in the Solar
System" (Rio de Janeiro, Brazil, 3-7 August, 2009), ed. by D. Lazzaro, D.
Prialnik, R. Schulz, J.A. Fernandez, submitte
Location of upper borders of cavities containing dust and gas under pressure in comets
The distance between the pre-impact surface of Comet 9P/Tempel 1 and the
upper border of the largest cavity excavated during ejection of material after
the collision of the impact module of the Deep Impact spacecraft with the comet
is estimated to be about 5-6 metres if the diameter of the DI transient crater
was about 150-200 m. The estimated distance was 4 m at the diameter was 100 m.
This result suggests that cavities containing dust and gas under pressure
located a few metres below surfaces of comets can be frequent.Comment: Monthly Notices of Royal Astronomical Society, 2012, in press, 7
page
Simulator for Microlens Planet Surveys
We summarize the status of a computer simulator for microlens planet surveys.
The simulator generates synthetic light curves of microlensing events observed
with specified networks of telescopes over specified periods of time.
Particular attention is paid to models for sky brightness and seeing,
calibrated by fitting to data from the OGLE survey and RoboNet observations in
2011. Time intervals during which events are observable are identified by
accounting for positions of the Sun and the Moon, and other restrictions on
telescope pointing. Simulated observations are then generated for an algorithm
that adjusts target priorities in real time with the aim of maximizing planet
detection zone area summed over all the available events. The exoplanet
detection capability of observations was compared for several telescopes.Comment: Proc. IAU Symp. No. 293 "Formation, detection, and characterization
of extrasolar habitable planets", ed. by N. Haghighipour. 4 pages, in pres
Simultaneous Triggered Collapse of the Presolar Dense Cloud Core and Injection of Short-Lived Radioisotopes by a Supernova Shock Wave
Cosmochemical evidence for the existence of short-lived radioisotopes (SLRI)
such as Al and Fe at the time of the formation of primitive
meteorites requires that these isotopes were synthesized in a massive star and
then incorporated into chondrites within yr. A supernova shock wave
has long been hypothesized to have transported the SLRI to the presolar dense
cloud core, triggered cloud collapse, and injected the isotopes. Previous
numerical calculations have shown that this scenario is plausible when the
shock wave and dense cloud core are assumed to be isothermal at K,
but not when compressional heating to K is assumed. We show here
for the first time that when calculated with the FLASH2.5 adaptive mesh
refinement (AMR) hydrodynamics code, a 20 km/sec shock wave can indeed trigger
the collapse of a 1 cloud while simultaneously injecting shock wave
isotopes into the collapsing cloud, provided that cooling by molecular species
such as HO, CO, and H is included. These calculations imply that
the supernova trigger hypothesis is the most likely mechanism for delivering
the SLRI present during the formation of the solar system.Comment: 12 pages, 4 color figures. Astrophysical Journal Letters (in press
Dynamical Zodiacal Cloud Models Constrained by High Resolution Spectroscopy of the Zodiacal Light (Icarus, in press)
The simulated Doppler shifts of the solar Mg I Fraunhofer line produced by
scattering on the solar light by asteroidal, cometary, and trans-Neptunian dust
particles are compared with the shifts obtained by Wisconsin H-Alpha Mapper
(WHAM) spectrometer. The simulated spectra are based on the results of
integrations of the orbital evolution of particles. The deviation of the
derived spectral parameters for various sources of dust used in the model
reached maximum at the elongation (measured eastward from the Sun) between 90
deg and 120 deg. For the future zodiacal light Doppler shifts measurements, it
is important to pay a particular attention to observing at this elongation
range. At the elongations of the fields observed by WHAM, the model-predicted
Doppler shifts were close to each other for several scattering functions
considered. Therefore the main conclusions of our paper don't depend on a
scattering function and mass distribution of particles if they are reasonable.
A comparison of the dependencies of the Doppler shifts on solar elongation and
the mean width of the Mg I line modeled for different sources of dust with
those obtained from the WHAM observations shows that the fraction of cometary
particles in zodiacal dust is significant and can be dominant. Cometary
particles originating inside Jupiter's orbit and particles originating beyond
Jupiter's orbit (including trans-Neptunian dust particles) can contribute to
zodiacal dust about 1/3 each, with a possible deviation from 1/3 up to 0.1-0.2.
The fraction of asteroidal dust is estimated to be about 0.3-0.5. The mean
eccentricities of zodiacal particles located at 1-2 AU from the Sun that better
fit the WHAM observations are between 0.2 and 0.5, with a more probable value
of about 0.3.Comment: Icarus, in pres