63 research outputs found
A preliminary reconstruction of the orbit of the Chelyabinsk Meteoroid
In February 15 2013 a medium-sized meteoroid impacted the atmosphere in the
region of Chelyabinsk, Russia. After its entrance to the atmosphere and after
travel by several hun- dred of kilometers the body exploded in a powerful event
responsible for physical damages and injured people spread over a region
enclosing several large cities. We present in this letter the results of a
preliminary reconstruction of the orbit of the Chelyabinsk meteoroid. Using
evidence gathered by one camera at the Revolution Square in the city of
Chelyabinsk and other videos recorded by witnesses in the close city of
Korkino, we calculate the trajectory of the body in the atmosphere and use it
to reconstruct the orbit in space of the meteoroid previous to the violent
encounter with our planet. In order to account for the uncertainties implicit
in the determination of the trajectory of the body in the atmosphere, we use
Monte Carlo methods to calculate the most probable orbital parameters. We use
this result to classify the meteoroid among the near Earth asteroid families
finding that the parent body belonged to the Apollo asteroids. Although
semimajor axis and inclination of the preliminary orbit computed by us are
uncertain, the rest of orbital elements are well constrained in this
preliminary reconstruction.Comment: 10 pages, 3 figures. Further details, updates, images, plots and
videos available at: http://astronomia.udea.edu.co/chelyabinsk-meteoroi
Revisiting the dynamics of planets in binaries: evolutionary timescales and the effect of early stellar evolution
The discovery of planets in binaries is one the most interesting outcomes of
planetary research. With the growing number of discoveries has also grown the
interest on describing their formation, long-term evolution and potential
habitability. In this work we revisit the dynamics of planets in S-type binary
systems. For that purpose we develop explicit formulas for the secularized
octupolar Hamiltonian, coupled with general relativistic corrections and
non-conservative interactions. We implemented those formulas in an open-source
package \texttt{SecDev3B}, that can be used to reproduce our results or test
improved versions of the models. In order to test it, we study the long-term
dynamical evolution of S-type binary planets during the pre-main-sequence phase
of stellar evolution. During that phase, stellar radius significantly changes
in timescales similar to secular timescales. We hypothesize that when
close-encounters between the planet and its host star happens (e.g. via
Lidov-Kozai effect), particularities in the secular formalism plus changes in
stellar radius may alter significantly the dynamical evolution. We study the
well-known binary planet HD 80606b and found that an octupolar expansion of the
conservative Hamiltonian is required to properly predict its dynamical
evolution. We also apply the dynamical model, enriched with results coming from
stellar evolutionary models, to demonstrate that in S-type systems around
low-mass stars, with relative high inclinations (\itot\ge 60^\circ), moderate
eccentricities () and planets located around 1 AU, the
evolution of stellar radius during the first few hundreds of Myr, alters
significantly the timescales of dynamical evolution.Comment: 20 pages, 7 figures, Submitted to MNRA
The orbit of the Chelyabinsk event impactor as reconstructed from amateur and public footage
A ballistic reconstruction of a meteoroid orbit can be made if enough
information is available about its trajectory inside the atmosphere. A few
methods have been devised in the past and used in several cases to trace back
the origin of small impactors. On February 15, 2013, a medium-sized meteoroid
hit the atmosphere in the Chelyabinsk region of Russia, causing damage in
several large cities. The incident, the largest registered since the Tunguska
event, was witnessed by many thousands and recorded by hundreds of amateur and
public video recording systems. The amount and quality of the information
gathered by those systems is sufficient to attempt a reconstruction of the
trajectory of the impactor body in the atmosphere, and from this the orbit of
the body with respect to the Sun. Using amateur and public footage taken in
four different places close to the event, we have determined precisely the
properties of the entrance trajectory and the orbit of the Chelyabinsk event
impactor. We found that the object entered the atmosphere at a velocity ranging
from 16.0 to 17.4 km/s in a grazing trajectory, almost directly from the east,
with an azimuth of velocity vector of 285, and with an elevation of
15.8 with respect to the local horizon. The orbit that best fits the
observations has, at a 95% confidence level, a semi-major axis a =
1.260.05 AU, eccentricity e = 0.440.03, argument of perihelion
=95.5 and longitude of ascending node =
326.5. Using these properties the object can be classified as
belonging to the Apollo family of asteroids. The absolute magnitude of the
meteoroid was H= 25.8, well below the threshold for its detection and
identification as a Potential Hazardous Asteroid (PHA). This result would imply
that present efforts intended to detect and characterize PHAs are incomplete.Comment: Submitted to Earth and Planetary Science Letters (EPSL), 10 pages, 4
figures, 3 tables. Supplementary information available at:
http://astronomia.udea.edu.co/chelyabinsk-meteoroi
Study of core collapse neutrino signals and constraints on neutrino masses from a future Galactic Supernova
We study the sensitivity to neutrino masses of a Galactic supernova neutrino
signal as could be measured with the detectors presently in operation and with
future large volume water \v{C}erencov and scintillator detectors. The analysis
uses the full statistics of neutrino events. The method proposed uses the
principles of Bayesian inference reasoning and has shown a remarkably
independence of astrophysical assumptions. We show that, after accounting for
the uncertainties in the detailed astrophysical description of the neutrino
signal and taking into account the effects of neutrino oscillations in the
supernova mantle, detectors presently in operation can have enough sensitivity
to reveal a neutrino mass (or to set upper limits) at the level of 1 eV. This
is sensibly better than present results from tritium -decay experiments,
competitive with the most conservative limits from neutrinoless double
-decay and less precise but remarkably less dependent from prior
assumptions than cosmological measurements. Future megaton water \v{C}erencov
detectors and large volume scintillator detectors will allow for about a factor
of two improvement in the sensitivity; however, they will not be competitive
with the next generation of tritium -decay and neutrinoless double
-decay experiments. Using the codes developed to perform the generation
of synthetic supernova signals and their analysis we created a computer
package, SUNG (SUpernova Neutrino Generation tool,
http://urania.udea.edu.co/sungweb), aimed to offer a general purpose solution
to perform calculations in supernova neutrino studies.Comment: 139 pp., Dissertation, Instituto de Fisica, Universidad de Antioqui
Correlation between tides and seismicity in Northwestern South America: the case of Colombia
We present the first systematic exploration of earth tides-seismicity
correlation in northwestern South America, with a special emphasis in Colombia.
For this purpose, we use a dataset of ~167,000 earthquakes, gathered by the
Colombian Seismological Network between 1993 and 2017. Most of the events are
intermediate-depth earthquakes from the Bucaramanga seismic nest and the Cauca
seismic cluster. For this purpose, we implemented a novel approach for the
calculation of tidal phases that considers the relative positions of the
Earth-Moon-Sun system at the time of the events. After applying the standard
Schuster test to the whole dataset and to several earthquake samples
(classified by time, location, magnitude and depth), we found strong
correlation anomalies with the diurnal and monthly components of the tide
(global log(p) values around -7.0 for the diurnal constituent and -12.1 for the
monthly constituent), especially for the intermediate depth events. These
anomalies suggest that around 16% of the deep earthquakes in Colombia may be
triggered by tides, especially when the monthly phase is between
350-10. We attribute our positive results, which favor the
tidal-triggering hypothesis, in contrast to previous negative ones to: 1) the
size of our dataset, and 2) the method we used to calculate tidal phases.
Anyone willing to reproduce our results or to apply our methodology to custom
datasets can use the public information system tQuakes that we developed for
this work.Comment: 49 pages, 19 figures. Accepter for publication in Journal of South
American Earth Sciences. tQuakes information System:
http://seap-udea.org/tQuake
Constraining the Radiation and Plasma Environment of the Kepler Circumbinary Habitable Zone Planets
The discovery of many planets using the Kepler telescope includes ten planets
orbiting eight binary stars. Three binaries, Kepler-16, Kepler-47, and
Kepler-453, have at least one planet in the circumbinary habitable-zone (BHZ).
We constrain the level of high-energy radiation and the plasma environment in
the BHZ of these systems. With this aim, BHZ limits in these Kepler binaries
are calculated as a function of time, and the habitability lifetimes are
estimated for hypothetical terrestrial planets and/or moons within the BHZ.
With the time-dependent BHZ limits established, a self-consistent model is
developed describing the evolution of stellar activity and radiation properties
as proxies for stellar aggression toward planetary atmospheres. Modeling binary
stellar rotation evolution, including the effect of tidal interaction between
stars in binaries is key to establishing the environment around these systems.
We find that Kepler-16 and its binary analogs provide a plasma environment
favorable for the survival of atmospheres of putative Mars-sized planets and
exomoons. Tides have modified the rotation of the stars in Kepler-47 making its
radiation environment less harsh in comparison to the solar system. This is a
good example of the mechanism first proposed by Mason et al. Kepler-453 has an
environment similar to that of the solar system with slightly better than Earth
radiation conditions at the inner edge of the BHZ. These results can be
reproduced and even reparametrized as stellar evolution and binary tidal models
progress, using our online tool http://bhmcalc.net.Comment: 18 pages, 9 figures. Accepted for publication in ApJ. It includes an
improved model for BHZ calculation and comparisons among different methods.
For reproducing these results and performing new ones please refer to the
Binary Habitability Calculator in http://bhmcalc.ne
The effect of close-in giant planets' evolution on tidal-induced migration of exomoons
Hypothetical exomoons around close-in giant planets may migrate inwards
and/or outwards in virtue of the interplay of the star, planet and moon tidal
interactions. These processes could be responsible for the disruption of lunar
systems, the collision of moons with planets or could provide a mechanism for
the formation of exorings. Several models have been developed to determine the
fate of exomoons when subject to the tidal effects of their host planet. None
of them have taken into account the key role that planetary evolution could
play in this process. In this paper we put together numerical models of exomoon
tidal-induced orbital evolution, results of planetary evolution and interior
structure models, to study the final fate of exomoons around evolving close-in
gas giants. We have found that planetary evolution significantly affects not
only the time-scale of exomoon migration but also its final fate. Thus, if any
change in planetary radius, internal mass distribution and rotation occurs in
time-scales lower or comparable to orbital evolution, exomoon may only migrate
outwards and prevent tidal disruption or a collision with the planet. If
exomoons are discovered in the future around close-in giant planets, our
results may contribute to constraint planetary evolution and internal structure
models.Comment: Published in Monthly Notices of the Royal Astronomical Society. 9
pages, 9 figure
Evolution of magnetic protection in potentially habitable terrestrial planets
We present a model for the evolution of the magnetic properties of habitable
terrestrial planets and their effects on the protection of planetary atmosphere
against the erosive action of stellar wind. Using up-to-date thermal evolution
models and dynamo scaling laws we predict the evolution of the planetary dipole
moment as a function of planetary mass and rotation rate. Combining these
results with models for the evolution of the stellar wind, stellar XUV fluxes
and planetary exosphere characteristics, we determine the properties of the
magnetosphere and the exobase radius in order to estimate the level of
atmospheric mass losses. We use this model to evaluate the magnetic protection
of the potentially habitable super-Earths GJ 667Cc, Gl 581d and HD 85512b. We
confirm that Earth-like planets, even under the highest attainable magnetic
field strengths, will lose a significant fraction of their atmospheric
volatiles if they are tidally locked in the habitable zone of dM stars, or even
if having N/O-rich atmospheres they are in habitable zones closer than
0.8 AU. Similar mass-dependent inner limits have been found for super-Earths
that in any case seem to have better chances of
preserving their atmospheres even if they are tidally locked. We predict that
the atmosphere of GJ 667Cc has probably already been obliterated and it is
presently uninhabitable. On the other hand, our model predicts that the
atmospheres of Gl 581d and HD 85512b would be well protected by intrinsic
magnetic fields, even under the worst expected conditions of stellar
aggression. (abrigded abstract).Comment: 17 pages, 11 figures; submitted to ApJ; comments are welcom
Towards a theoretical determination of the geographical probability distribution of meteoroid impacts on Earth
Tunguska and Chelyabinsk impact events occurred inside a geographical area of
only 3.4\% of the Earth's surface. Although two events hardly constitute a
statistically significant demonstration of a geographical pattern of impacts,
their spatial coincidence is at least tantalizing. To understand if this
concurrence reflects an underlying geographical and/or temporal pattern, we
must aim at predicting the spatio-temporal distribution of meteoroid impacts on
Earth. For this purpose we designed, implemented and tested a novel numerical
technique, the "Gravitational Ray Tracing" (GRT) designed to compute the
relative impact probability (RIP) on the surface of any planet. GRT is inspired
by the so-called ray-casting techniques used to render realistic images of
complex 3D scenes. In this paper we describe the method and the results of
testing it at the time of large impact events. Our findings suggest a
non-trivial pattern of impact probabilities at any given time on Earth.
Locations at from the apex are more prone to impacts, especially at
midnight. Counterintuitively, sites close to apex direction have the lowest
RIP, while in the antapex RIP are slightly larger than average. We present here
preliminary maps of RIP at the time of Tunguska and Chelyabinsk events and
found no evidence of a spatial or temporal pattern, suggesting that their
coincidence was fortuitous. We apply the GRT method to compute theoretical RIP
at the location and time of 394 large fireballs. Although the predicted
spatio-temporal impact distribution matches marginally the observed events, we
successfully predict their impact speed distribution.Comment: 16 pages, 11 figures. Accepted for publication in MNRA
A general method for assessing the origin of interstellar small bodies: the case of 1I/2017 U1 ('Oumuamua)
With the advent of more and deeper sky surveys, the discovery of interstellar
small objects entering into the Solar System has been finally possible. In
October 19, 2017, using observations of the Pan-STARRS survey, a fast moving
object, now officially named 1I/2017 U1 ('Oumuamua), was discovered in a
heliocentric unbound trajectory suggesting an interstellar origin. Assessing
the provenance of interstellar small objects is key for understanding their
distribution, spatial density and the processes responsible for their ejection
from planetary systems. However, their peculiar trajectories place a limit on
the number of observations available to determine a precise orbit. As a result,
when its position is propagated years backward in time, small
errors in orbital elements become large uncertainties in position in the
interstellar space. In this paper we present a general method for assigning
probabilities to nearby stars of being the parent system of an observed
interstellar object. We describe the method in detail and apply it for
assessing the origin of 'Oumuamua. A preliminary list of potential progenitors
and their corresponding probabilities is provided. In the future, when further
information about the object and/or the nearby stars be refined, the
probabilities computed with our method can be updated. We provide all the data
and codes we developed for this purpose in the form of an open source {\tt
C/C++/Python package}, {\bf\tt iWander} which is publicly available at
http://github.com/seap-udea/iWander.Comment: 16 pages, 8 figures. Accepted for publication in the Astronomical
Journal. iWander package available at http://github.com/seap-udea/iWande
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