We have undertaken a thorough dynamical investigation of five extrasolar planetary systems using ... more We have undertaken a thorough dynamical investigation of five extrasolar planetary systems using extensive numerical experiments. The systems Gl 777 A, HD 72659, Gl 614, 47 Uma and HD 4208 were examined concerning the question of whether they could host terrestrial like planets in their habitable zones (=HZ). First we investigated the mean motion resonances between fictitious terrestrial planets and the existing gas giants in these five extrasolar systems. Then a fine grid of initial conditions for a potential terrestrial planet within the HZ was chosen for each system, from which the stability of orbits was then assessed by direct integrations over a time interval of 1 million years. The computations were carried out using a Lie-series integration method with an adaptive step size control. This integration method achieves machine precision accuracy in a highly efficient and robust way, requiring no special adjustments when the orbits have large eccentricities. The stability of orbits was examined with a determination of the Renyi entropy, estimated from recurrence plots, and with a more straight forward method based on the maximum eccentricity achieved by the planet over the 1 million year integration. Additionally, the eccentricity is an indication of the habitability of a terrestrial planet in the HZ; any value of e>0.2 produces a significant temperature difference on a planet's surface between apoapse and periapse. The results for possible stable orbits for terrestrial planets in habitable zones for the five systems are summarized as follows: for Gl 777 A nearly the entire HZ is stable, for 47 Uma, HD 72659 and HD 4208 terrestrial planets can survive for a sufficiently long time, while for Gl 614 our results exclude terrestrial planets moving in stable orbits within the HZ.
Monthly Notices of The Royal Astronomical Society, 2007
This paper is the first in a series of publications which investigate the stability properties of... more This paper is the first in a series of publications which investigate the stability properties of the complete set of isothermal protoplanetary equilibrium solutions. To perform a non-linear stability analysis, we introduce a fluid dynamics numerical model. We inspect the entire solution set and find five basic dynamical modes: oscillation, pulsation, transition, ejection and collapse.
We present a model for the equilibrium of solid planetary cores embedded in a gaseous nebula. Fro... more We present a model for the equilibrium of solid planetary cores embedded in a gaseous nebula. From this model we are able to extract an idealized roadmap of all hydrostatic states of the isothermal protoplanets. The complete classification of the isothermal protoplanetary equilibria should improve the understanding of the general problem of giant planet formation, within the framework of the nucleated instability hypothesis. We approximate the protoplanet as a spherically symmetric, isothermal, self-gravitating classical ideal gas envelope in equilibrium, around a rigid body of given mass and density, with the gaseous envelope required to fill the Hill-sphere. Starting only with a core of given mass and an envelope gas density at the core surface, the equilibria are calculated without prescribing the total protoplanetary mass or nebula density. The static critical core masses of the protoplanets for the typical orbits of 1, 5.2, and 30 AU, around a parent star of 1 solar mass are found to be 0.1524, 0.0948, and 0.0335 Earth masses, respectively, for standard nebula conditions (Kusaka et al. 1970). These values are much lower than currently admitted ones primarily because our model is isothermal and the envelope is in thermal equilibrium with the nebula. For a given core, multiple solutions (at least two) are found to fit into the same nebula. We extend the concept of the static critical core mass to the local and global critical core mass. We conclude that the 'global static critical core mass' marks the meeting point of all four qualitatively different envelope regions.
We propose a quantitative concept for the lower planetary boundary, requiring that a planet must ... more We propose a quantitative concept for the lower planetary boundary, requiring that a planet must keep its atmosphere in vacuum. The solution-set framework of Pečnik and Wuchterl (2005) enabled a clear and quantitative criterion for the discrimination of a planet and a minor body. Using a simple isothermal core-envelope model, we apply the proposed planetary criterion to the large bodies in the Solar System.
This paper identifies new ideas for using existing space technologies as spin-offs and considers ... more This paper identifies new ideas for using existing space technologies as spin-offs and considers the effectiveness of the use of such technologies for various industries and applications. It then explores the dissemination of knowledge and information about such spinoff technology and applications to various audiences. It proposes methods to improve the dissemination of such knowledge and information. The paper concludes with some recommendations on how the dissemination of information about space spin-offs can increase awareness and use of such technology and, in the long term, increase support for space activities. The perspective of this article is that of the world's various space agencies and the UN Committee on the Peaceful Uses of Outer Space (UNCOPUOS). It is recognized that truly effective spin-offs depend on the involvement of those outside the space arena, particularly the commercial, academic and governmental sectors. These sectors and the general public must see the value and cost efficiency of 'spin-offs' and of developing new technology and systems through space research programs or they will not succeed. This may require space agencies to stay more focused on research and to hand over functions and activities to these 'outside sectors' once 'seeds are planted'. r
We have undertaken a thorough dynamical investigation of five extrasolar planetary systems using ... more We have undertaken a thorough dynamical investigation of five extrasolar planetary systems using extensive numerical experiments. The systems Gl 777 A, HD 72659, Gl 614, 47 Uma and HD 4208 were examined concerning the question of whether they could host terrestrial like planets in their habitable zones (=HZ). First we investigated the mean motion resonances between fictitious terrestrial planets and the existing gas giants in these five extrasolar systems. Then a fine grid of initial conditions for a potential terrestrial planet within the HZ was chosen for each system, from which the stability of orbits was then assessed by direct integrations over a time interval of 1 million years. The computations were carried out using a Lie-series integration method with an adaptive step size control. This integration method achieves machine precision accuracy in a highly efficient and robust way, requiring no special adjustments when the orbits have large eccentricities. The stability of orbits was examined with a determination of the Renyi entropy, estimated from recurrence plots, and with a more straight forward method based on the maximum eccentricity achieved by the planet over the 1 million year integration. Additionally, the eccentricity is an indication of the habitability of a terrestrial planet in the HZ; any value of e>0.2 produces a significant temperature difference on a planet's surface between apoapse and periapse. The results for possible stable orbits for terrestrial planets in habitable zones for the five systems are summarized as follows: for Gl 777 A nearly the entire HZ is stable, for 47 Uma, HD 72659 and HD 4208 terrestrial planets can survive for a sufficiently long time, while for Gl 614 our results exclude terrestrial planets moving in stable orbits within the HZ.
Monthly Notices of The Royal Astronomical Society, 2007
This paper is the first in a series of publications which investigate the stability properties of... more This paper is the first in a series of publications which investigate the stability properties of the complete set of isothermal protoplanetary equilibrium solutions. To perform a non-linear stability analysis, we introduce a fluid dynamics numerical model. We inspect the entire solution set and find five basic dynamical modes: oscillation, pulsation, transition, ejection and collapse.
We present a model for the equilibrium of solid planetary cores embedded in a gaseous nebula. Fro... more We present a model for the equilibrium of solid planetary cores embedded in a gaseous nebula. From this model we are able to extract an idealized roadmap of all hydrostatic states of the isothermal protoplanets. The complete classification of the isothermal protoplanetary equilibria should improve the understanding of the general problem of giant planet formation, within the framework of the nucleated instability hypothesis. We approximate the protoplanet as a spherically symmetric, isothermal, self-gravitating classical ideal gas envelope in equilibrium, around a rigid body of given mass and density, with the gaseous envelope required to fill the Hill-sphere. Starting only with a core of given mass and an envelope gas density at the core surface, the equilibria are calculated without prescribing the total protoplanetary mass or nebula density. The static critical core masses of the protoplanets for the typical orbits of 1, 5.2, and 30 AU, around a parent star of 1 solar mass are found to be 0.1524, 0.0948, and 0.0335 Earth masses, respectively, for standard nebula conditions (Kusaka et al. 1970). These values are much lower than currently admitted ones primarily because our model is isothermal and the envelope is in thermal equilibrium with the nebula. For a given core, multiple solutions (at least two) are found to fit into the same nebula. We extend the concept of the static critical core mass to the local and global critical core mass. We conclude that the 'global static critical core mass' marks the meeting point of all four qualitatively different envelope regions.
We propose a quantitative concept for the lower planetary boundary, requiring that a planet must ... more We propose a quantitative concept for the lower planetary boundary, requiring that a planet must keep its atmosphere in vacuum. The solution-set framework of Pečnik and Wuchterl (2005) enabled a clear and quantitative criterion for the discrimination of a planet and a minor body. Using a simple isothermal core-envelope model, we apply the proposed planetary criterion to the large bodies in the Solar System.
This paper identifies new ideas for using existing space technologies as spin-offs and considers ... more This paper identifies new ideas for using existing space technologies as spin-offs and considers the effectiveness of the use of such technologies for various industries and applications. It then explores the dissemination of knowledge and information about such spinoff technology and applications to various audiences. It proposes methods to improve the dissemination of such knowledge and information. The paper concludes with some recommendations on how the dissemination of information about space spin-offs can increase awareness and use of such technology and, in the long term, increase support for space activities. The perspective of this article is that of the world's various space agencies and the UN Committee on the Peaceful Uses of Outer Space (UNCOPUOS). It is recognized that truly effective spin-offs depend on the involvement of those outside the space arena, particularly the commercial, academic and governmental sectors. These sectors and the general public must see the value and cost efficiency of 'spin-offs' and of developing new technology and systems through space research programs or they will not succeed. This may require space agencies to stay more focused on research and to hand over functions and activities to these 'outside sectors' once 'seeds are planted'. r
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