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Register a new userSpace-borne global astrometric surveys: the hunt for extra-solar planets
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Added by
Alessandro Sozzetti
Publication date
2000
fields
Physics
and research's language is
English
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The proposed global astrometry mission {it GAIA}, recently recommended within the context of ESAs Horizon 2000 Plus long-term scientific program, appears capable of surveying the solar neighborhood within $sim$ 200 pc for the astrometric signatures of planets around stars down to the magnitude limit of $V$=17 mag, which includes late M dwarfs at 100 pc. Realistic end-to-end simulations of the GAIA global astrometric measurements have yielded first quantitative estimates of the sensitivity to planetary perturbations and of the ability to measure their orbital parameters. Single Jupiter-mass planets around normal solar-type stars appear detectable up to 150 pc ($Vle $12 mag) with probabilities $ge$ 50 per cent for orbital periods between $sim$2.5 and $sim$8 years, and their orbital parameters measured with better than 30 per cent accuracy to about 100 pc. Jupiter-like objects (same mass and period as our giant planet) are found with similar probabilities up to 100 pc.These first experiments indicate that the {it GAIA} results would constitute an important addition to those which will come from the other ongoing and planned planet-search programs. These data combined would provide a formidable testing ground on which to confront theories of planetary formation and evolution.
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We present the results of realistic end-to-end simulations of observations of nearby stars with the proposed global astrometry mission GAIA, recently recommended within the context of ESAs Horizon 2000 Plus long-term scientific program. We show that under realistic, if challenging, assumptions, GAIA will be capable of surveying the solar neighborhood within 100-200 pc for the astrometric signatures of planets around stars down to V = 16 mag. The wealth of results on the frequency and properties of massive planets from GAIA observations will provide a formidable testing ground on which to confront the most sophisticated theories on planetary formation and evolution. Finally, we suggest the possibility of more sophisticated probabilistic detection techniques which may be able to detect the presence of Earth-like planets around stars within 20 pc.
We introduce a new method of searching for and characterizing extra-solar planets. We show that by monitoring the center-of-light motion of microlensing alerts using the next generation of high precision astrometric instruments the probability of detecting a planet orbiting the lens is high. We show that adding astrometric information to the photometric microlensing lightcurve greatly helps in determining the planetary mass and semi-major axis. We introduce astrometric maps as a new way for calculating astrometric motion and planet detection probabilities. Finite source effects are important for low mass planets, but even Earth mass planets can give detectable signals.
This paper summarizes the information gathered for 16 still unpublished exoplanet candidates discovered with the CORALIE echelle spectrograph mounted on the Euler Swiss telescope at La Silla Observatory. Amongst these new candidates, 10 are typical extrasolar Jupiter-like planets on intermediate- or long-period (100<P<1350d) and fairly eccentric (0.2<e<0.5) orbits (HD19994, HD65216, HD92788, HD111232, HD114386, HD142415, HD147513, HD196050, HD216437, HD216770). Two of these stars are in binary systems. The next 3 candidates are shorter-period planets (HD6434, HD121504) with lower eccentricities among which a hot Jupiter (HD83443). More interesting cases are finally given by the multiple-planet systems HD82943 and HD169830. The former is a resonant P_2/P_1=2/1 system in which planet-planet interactions are influencing the system evolution. The latter is more hierarchically structured.
Precise radial-velocity observations at Haute-Provence Observatory (OHP, France) with the ELODIE echelle spectrograph have been undertaken since 1994. In addition to several discoveries described elsewhere, including and following that of 51 Peg b, they reveal new sub-stellar companions with essentially moderate to long periods. We report here about such companions orbiting five solar-type stars (HD 8574, HD 23596, HD 33636, HD 50554, HD 106252) and one sub-giant star (HD 190228). The companion of HD 8574 has an intermediate period of 227.55 days and a semi--major axis of 0.77 AU. All other companions have long periods, exceeding 3 years, and consequently their semi-major axes are around or above 2 AU. The detected companions have minimum masses m2sini ranging from slightly more than 2 M_Jup to 10.6 M_Jup. These additional objects reinforce the conclusion that most planetary companions have masses lower than 5 M_Jup but with a tail of the mass distribution going up above 15 M_Jup. The orbits are all eccentric and 4 out of 6 have an eccentricity of the order of 0.5. Four stars exhibit solar metallicity, one is metal-rich and one metal-poor. With 6 new extra-solar planet candidates discovered, increasing their total known to-date number to 115, the ELODIE Planet Search Survey yield is currently 18. We emphasize that 3 out of the 6 companions could in principle be resolved by diffraction-limited imaging on 8m-class telescopes depending on the achievable contrast, and therefore be primary targets for first attempts of extra-solar planet direct imaging.
Global scale quantum communication links will form the backbone of the quantum internet. However, exponential loss in optical fibres precludes any realistic application beyond few hundred kilometres. Quantum repeaters and space-based systems offer to overcome this limitation. Here, we analyse the use of quantum memory (QM)-equipped satellites for quantum communication focussing on global range repeaters and Measurement-Device-Independent (MDI) QKD. We demonstrate that satellites equipped with QMs provide three orders of magnitude faster entanglement distribution rates than existing protocols based on fibre-based repeaters or space systems without QMs. We analyse how entanglement distribution performance depends on memory characteristics, determine benchmarks to assess performance of different tasks, and propose various architectures for light-matter interfaces. Our work provides a practical roadmap to realise unconditionally secure quantum communications over global distances with current technologies.
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