5 research outputs found
A Comment on "The Far Future of Exoplanet Direct Characterization" - the Case for Interstellar Space Probes
Following on from ideas presented in a recent paper by Schneider et al.
(2010) on "The Far Future of Exoplanet Direct Characterization", I argue that
they have exaggerated the technical obstacles to performing such 'direct
characterization' by means of fast (order 0.1c) interstellar space probes. A
brief summary of rapid interstellar spaceflight concepts that may be found in
the literature is presented. I argue that the presence of interstellar dust
grains, while certainly something which will need to be allowed for in
interstellar vehicle design, is unlikely to be the kind of 'show stopper'
suggested by Schneider et al. Astrobiology as a discipline would be a major
beneficiary of developing an interstellar spaceflight capability, albeit in the
longer term, and I argue that astrobiologists should keep an open mind to the
possibilities.Comment: Accepted for publication in Astrobiolog
Constraining the electric charges of some astronomical bodies in Reissner-Nordstrom spacetimes and generic r^-2-type power-law potentials from orbital motions
We put model-independent, dynamical constraints on the net electric charge Q
of some astronomical and astrophysical objects by assuming that their exterior
spacetimes are described by the Reissner-Nordstroem metric, which induces an
additional potential U_RN \propto Q^2 r^-2. Our results extend to other
hypothetical power-law interactions inducing extra-potentials U_pert = r^-2 as
well (abridged).Comment: LaTex2e, 16 pages, 3 figures, no tables, 128 references. Version
matching the one at press in General Relativity and Gravitation (GRG). arXiv
admin note: substantial text overlap with arXiv:1112.351