Dark Earths: Initial Goals for Interstellar Exploration (original) (raw)
Related papers
Chasing Nomadic Worlds: A New Class of Deep Space Missions
2022
Nomadic worlds are objects not bound to any star(s), and are of great interest to planetary science and astrobiology. They have garnered attention recently on account of their detection in microlensing surveys and also from the recent discovery of interstellar planetesimals. In this paper, we evaluate the prevalence of nomadic worlds with radii of 100 km ≲ R ≲ 10 4 km, which might permit habitable conditions. The cumulative number density n > (> R) appears to follow a heuristic power law given by n > ∝ R −3. Therefore, smaller objects should be much more numerous than the largest rocky nomadic planets, and thus statistically more likely to have members relatively close to the inner Solar system. Our results suggest that tens to hundreds of planet-sized nomadic worlds may populate the spherical volume centered on Earth and circumscribed by Proxima Centauri, and thus may comprise closer interstellar targets than any stellar planetary system. For the first time, we systematically analyze the feasibility of exploring these unbounded celestial bodies via deep space missions. We investigate what near-future propulsion systems could theoretically enable us to reach nomadic worlds (of radius > R) on a 50-year timescale. Objects with R ∼ 100 km are within the purview of multiple propulsion methods such as electric sails, laser electric propulsion, and solar sails. In contrast, nomadic worlds with R ≳ 1000 km are accessible by laser sails (and perhaps nuclear fusion), thereby underscoring their vast potential for deep space exploration.
Comments Astrophys., 1990
The presence of unseen mass in the solar neighbourhood has prompted modelling of, and searches for, a population of cool, low mass stars to make up the deficit. Such brown dwarfs are thought to exist within a mass range of 0.01 M⊙ < M < 0.08 M⊙. In this paper the possibility of the existence of interstellar planets (ISPs) of mass range 5x10^-9 M⊙ < M < 0.01 M⊙ is examined. Six potential modes of formation of ISPs are identified, although some are mutually exclusive, depending of different cosmogonic hypotheses. ISPs are of two basic types: those formed solitary within molecular clouds and those formed within, and subsequently unbound from, planetary systems. While the existence of the former is uncertain, interstellar planets of the unbound variety almost definitely exist, although not in sufficient quantity to account for the unseen mass. The number density of unbound planets in the solar neighbourhood may be of a similar, or greater, order of magnitude to that of stars, the majority of them being massive planetesimals ejected from planetary systems in formation. The nearest extra-solar planet may thus be closer to the solar system than the nearest star.
Nomadic Planets Near the Solar System
Gravitational microlensing has revealed an extensive population of “nomadic” planets not orbiting any star, with Jupiter-mass nomads being more populous than main sequence stars. Except for distant objects discovered through microlensing, and hot, young nomads found near star formation regions, to date only a small number of nomad candidates have been discovered. Here I show that there should be significant numbers of mature nomadic exoplanets close enough to be discovered with existing or planned astronomical resources, including possibly dozens of massive planets closer than the nearest star. Observational data are used to derive models relating mass, radius, heat flux and magnetic dipole moment; these are used to show the observability of nomads in the IR, due to thermal emissions, and at radio frequencies, due to cyclotron maser instabilities. These neighboring nomadic planets will provide a new exoplanet population for astronomical research and, eventually, direct exploration by spacecraft.
Chasing Shadows in the Outer Solar System
2010
The characteristics of the populations of objects that inhabit the outer solar system carry the fingerprint of the processes that governed the formation and evolution of the solar system. Occultation surveys push the limit of observation into the very small and distant outer solar system objects, allowing us to set constraints on the structure of the Kuiper belt, Scattered disk and Sedna populations. I collected, reduced, and analyzed vast datasets looking for occultations of stars by outer solar system objects, both working with the Taiwanese American Occultation Survey (TAOS) collaboration and leading the MMT/Megacam occultation effort. Having found no such events in my data, I was able to place upper limits on the Kuiper belt, scattered disk and Sedna population. These limits and their derivation are described here. Degree Type Dissertation Degree Name Doctor of Philosophy (PhD) Graduate Group Physics & Astronomy First Advisor Charles R. Alcock Second Advisor Pavlos Protopapas Th...