- Medellín, Antioquia, Colombia
Jorge Callejas
Universidad de Antioquia, Instituto de Física, Faculty Member
On April 13, 2029, asteroid \Apophis will pass within {six} Earth radii ($\sim$31000 km above surface), in what will be the closest approach of this asteroid in recorded history. This event provides unique scientific opportunities to... more
On April 13, 2029, asteroid \Apophis will pass within {six} Earth radii ($\sim$31000 km above surface), in what will be the closest approach of this asteroid in recorded history. This event provides unique scientific opportunities to study the asteroid, its orbit, and surface characteristics at an exceptionally close distance. In this paper we perform a synthetic geometrical, geographical and temporal analysis of the conditions under which the asteroid can be observed from Earth, with a particular emphasis on the conditions and scientific opportunities for bistatic radar observations, the only feasible radar technique applicable in such a close approach. For this purpose, we compile a list of present and future radio observatories around the globe which could participate in bistatic radar observation campaigns during the closest approach of Apophis. We estimate power, signal-to-noise ratios, surface coverage and other observing conditions. We find that a global collaboration of obse...
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Es un hecho bien conocido que la materia oscura representa la mayor parte del contenido material del universo y por ello las simulaciones cosmologicas que estudian la dinamica en volumenes considerables de espacio no necesitan incluir la... more
Es un hecho bien conocido que la materia oscura representa la mayor parte del contenido material del universo y por ello las simulaciones cosmologicas que estudian la dinamica en volumenes considerables de espacio no necesitan incluir la componente barionica. Palabras clave: Programacion paralela usando paso de mensajes. Simulaciones Cosmologicas, Modelo ACDM, Recetas semianaliticas.
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1647 b Z. E. González, J. I. Zuluaga and P. A. Mason . Asociación Multidisciplinaria de Estudios en Biología y Astrobiología (AMEBA), Solar, Earth and Planetary Physics Group (SEAP), Instituto de Física – FCEN, Universi dad de Antioquia,... more
1647 b Z. E. González, J. I. Zuluaga and P. A. Mason . Asociación Multidisciplinaria de Estudios en Biología y Astrobiología (AMEBA), Solar, Earth and Planetary Physics Group (SEAP), Instituto de Física – FCEN, Universi dad de Antioquia, Calle 70 No 52-21, Medellín, Colombia, zusi.gonzalez@udea.edu.co, jorge.zuluaga@udea.edu.co , New Mexico State University – DACC, Las Cruces, NM, 88003, USA, pmason@nmsu.edu .
Compressible, Riemann S-type ellipsoids can emit gravitational waves (GWs) with a chirp-like behavior (hereafter chirping ellipsoids, CELs). We show that the GW frequency-amplitude evolution of CELs (mass $\sim 1$~M$_\odot$, radius... more
Compressible, Riemann S-type ellipsoids can emit gravitational waves (GWs) with a chirp-like behavior (hereafter chirping ellipsoids, CELs). We show that the GW frequency-amplitude evolution of CELs (mass $\sim 1$~M$_\odot$, radius $\sim10^3$~km, polytropic equation of state with index $n\approx 3$) is indistinguishable from that emitted by double white dwarfs (DWDs) and by extreme mass-ratio inspirals (EMRIs) composed of an intermediate-mass (e.g.~$10^3~M_\odot$) black hole and a planet-like (e.g.~$10^{-4}~M_\odot$) companion, in a specific frequency interval within the detector sensitivity band in which the GWs of all these systems are quasi-monochromatic. We estimate that for reasonable astrophysical assumptions, the rates in the local Universe of CELs, DWDs and EMRIs in the mass range considered here, are very similar, posing a detection-degeneracy challenge for space-based GW detectors. The astrophysical implications of this CEL-binary detection degeneracy by space-based GW-det...
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Enceladus is a potential target for future astrobiological missions. NASA’s Cassini spacecraft demonstrated that the Saturnian moon harbors a salty ocean beneath its icy crust and the existence and analysis of the plume suggest water–rock... more
Enceladus is a potential target for future astrobiological missions. NASA’s Cassini spacecraft demonstrated that the Saturnian moon harbors a salty ocean beneath its icy crust and the existence and analysis of the plume suggest water–rock reactions, consistent with the possible presence of hydrothermal vents. Particularly, the plume analysis revealed the presence of molecular hydrogen, which may be used as an energy source by microorganisms ( e.g., methanogens). This could support the possibility that populations of methanogens could establish in such environments if they exist on Enceladus. We took a macroscale approximation using ecological niche modeling to evaluate whether conditions suitable for methanogenic archaea on Earth are expected in Enceladus. In addition, we employed a new approach for computing the biomass using the Monod growth model. The response curves for the environmental variables performed well statistically, indicating that simple correlative models may be use...
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During lunar eclipse of 2019 January 21, a meteoroid impacted the Moon producing a visible light flash. The impact was witnessed by casual observers offering an opportunity to study the phenomenon from multiple geographical locations. We... more
During lunar eclipse of 2019 January 21, a meteoroid impacted the Moon producing a visible light flash. The impact was witnessed by casual observers offering an opportunity to study the phenomenon from multiple geographical locations. We use images and videos collected by observers in seven countries to estimate the location, impact parameters (speed and incoming direction), and energy of the meteoroid. Using parallax, we achieve determining the impact location at lat.$-29.43^{+0.30}_{-0.21}$, lon.$-67.89^{+0.07}_{-0.09}$, and geocentric distance as 356 553 km. After devising and applying a photometric procedure for measuring flash standard magnitudes in multiple RGB images having different exposure times, we found that the flash, had an average G-magnitude 〈G〉 = 6.7 ± 0.3. We use gravitational ray tracing (GRT) to estimate the orbital properties and likely radiant of the impactor. We find that the meteoroid impacted the moon with a speed of $14^{+7}_{-6}$ km s−1 (70 per cent C.L.) ...
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Exoplanet discoveries have motivated numerous efforts to find unseen populations of exomoons, yet they have been unsuccessful. A plausible explanation is that most discovered planets are located on close-in orbits, which would make their... more
Exoplanet discoveries have motivated numerous efforts to find unseen populations of exomoons, yet they have been unsuccessful. A plausible explanation is that most discovered planets are located on close-in orbits, which would make their moons prone to tidal evolution and orbital detachment. In recent models of tidally driven migration of exomoons, evolving planets might prevent what was considered their most plausible fate (i.e. colliding against their host planet), favouring scenarios where moons are pushed away and reach what we define as the satellite tidal orbital parking distance ($a_{\rm \mathrm{stop}}$), which is often within the critical limit for unstable orbits and depends mainly on the system’s initial conditions: mass ratio, semimajor axes, and rotational rates. Using semi-analytical calculations and numerical simulations, we calculate $a_{\rm \mathrm{stop}}$ for different initial system parameters and constrain the transit detectability of exomoons around close-in plan...
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In July 5th 2014 an occultation of Mars by the Moon was visible in South America. Citizen scientists and professional astronomers in Colombia, Venezuela and Chile performed a set of simple observations of the phenomenon aimed to measure... more
In July 5th 2014 an occultation of Mars by the Moon was visible in South America. Citizen scientists and professional astronomers in Colombia, Venezuela and Chile performed a set of simple observations of the phenomenon aimed to measure the speed of light and lunar distance. This initiative is part of the so called "Aristarchus Campaign", a citizen astronomy project aimed to reproduce observations and measurements made by astronomers of the past. Participants in the campaign used simple astronomical instruments (binoculars or small telescopes) and other electronic gadgets (cell-phones and digital cameras) to measure occultation times and to take high resolution videos and pictures. In this paper we describe the results of the Aristarchus Campaign. We compiled 9 sets of observations from sites separated by distances as large as 2,500 km. We achieve at measuring the speed of light in vacuum and lunar distance with uncertainties of few percent. The goal of the Aristarchus Cam...
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ABSTRACT Limits on the potential habitability of exomoons orbiting massive planets within circumbinary habitable zones are examined. Exomoons orbiting planets in the habitable zones of single stars and those orbiting circumbinary planets... more
ABSTRACT Limits on the potential habitability of exomoons orbiting massive planets within circumbinary habitable zones are examined. Exomoons orbiting planets in the habitable zones of single stars and those orbiting circumbinary planets are subject to the, sometimes intense, tidal heating of the planet. So, exomoon orbits need to be sufficiently large and circular to avoid loss of water like Io. However, moons may be lost if their orbits are too large. We show that, in some cases, massive circumbinary planets have larger Hill radii than similar mass planets in single star habitable zones. The range of semimajor axes, beyond the habitable edge for moons is several times larger in some binaries as compared to single stars and is verified by numerical orbit experiments. We discuss implications of this result in the context of the binary habitability mechanism.
Research Interests: Planet and Habitability
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In this paper we discuss and illustrate the hypothesis that life substantially alters the state of a planetary environment and therefore, modifies the limits of the HZ as estimated for an uninhabited planet. This hypothesis lead to the... more
In this paper we discuss and illustrate the hypothesis that life substantially alters the state of a planetary environment and therefore, modifies the limits of the HZ as estimated for an uninhabited planet. This hypothesis lead to the introduction of the Habitable Zone for Inhabited Planets (hereafter InHZ), defined here as the region where the complex interaction between life and its abiotic environment is able to produce plausible equilibrium states with the necessary physical conditions for the existence and persistence of life itself. We support our hypothesis of an InHZ with three theoretical arguments, multiple evidences coming from observations of the Earth system, several conceptual experiments and illustrative numerical simulations. Conceptually the diference between the InHZ and the Abiotic HZ (AHZ) depends on unique and robust properties of life as an emergent physical phenomenon and not necesarily on the particular life forms bearing in the planet. Our aim here is to pr...
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La investigación científica y tecnológica se apoya cada vez más en sistemas de cómputo de alto desempeño para incrementar su calidad y alcances. Para lograr sistemas de este tipo en el contexto colombiano, se requiere lograr la... more
La investigación científica y tecnológica se apoya cada vez más en sistemas de cómputo de alto desempeño para incrementar su calidad y alcances. Para lograr sistemas de este tipo en el contexto colombiano, se requiere lograr la integración los recursos limitados existentes ...
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Non homogeneous axisymmetric models of self-gravitating systems are discussed by using functional methods and numerical techinques. More in detail, in a reference frame, rotating with constant angular velocity Omega, a self-gravitating... more
Non homogeneous axisymmetric models of self-gravitating systems are discussed by using functional methods and numerical techinques. More in detail, in a reference frame, rotating with constant angular velocity Omega, a self-gravitating incompressible fluid, in steady state is considered. In particular the internal velocity field has flow lines normal to the global angular velocity. Deriving a generalized Lane-Emden equation and using a procedure inspired by the method of Eriguchi-Muller, for selected velocity profiles, a sequence of equilibrium configurations is found and discussed.
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A functional method developed for analyzing rotating self-gravitating fluid is discussed in relation with selected velocity profiles. Specific numerical techniques developed in the past for the solution of the problem are adopted.