Although ESA has cancelled its Eddington mission, which was to have used a precision photometer to record the transit of planets across the disks of distant stars, the agency is pressing ahead with a mission that will compile a catalog of up to a billion stars. As described in the ESA press release, the Gaia mission would be launched in 2010, and would spend almost a decade plotting these stars into a three-dimensional grid that would show not just their current position, but direction of motion, color and composition.
It always startles me how little we know about even nearby stars. It was only last year that the red dwarf SO25300.5+165258 was discovered, but at 7.8 light years away, it is the third closest star to the Sun. Projects like Gaia will be invaluable at filling in our information about other close stars that have so far evaded detection, many of them simply because of their size and dimness — some 70 percent of all stars in the galaxy are type M red dwarfs like Proxima Centauri. They’re tiny, nondescript, and when they’re close, the fact can only be uncovered by studies of their motion against background stars. We have a lot of work ahead of us just to map the immediate stellar neighborhood. And if one billion stars sounds like a lot, recall that there are some 100 billion in the galaxy at large.
Testing Planet Formation Models with Gaia $\mu$as Astrometry
Authors: A. Sozzetti (1,2), S. Casertano (3), M.G. Lattanzi (2), A. Spagna (1), R. Morbidelli (2), R. Pannunzio (2), D. Pourbaix (4), D. Queloz (5) ((1) CfA, (2) OATo, (3) STScI, (4)ULB, (5)Geneva)
(Submitted on 30 Nov 2007)
Abstract: In this paper, we first summarize the results of a large-scale double-blind tests campaign carried out for the realistic estimation of the Gaia potential in detecting and measuring planetary systems. Then, we put the identified capabilities in context by highlighting the unique contribution that the Gaia exoplanet discoveries will be able to bring to the science of extrasolar planets during the next decade.
Comments: 4 pages, 1 figure. To appear in the proceedings of “IAU Symposium 248 – A Giant Step: from Milli- to Micro-arcsecond Astrometry”, held in Shanghai, China, 15-19 Oct. 2007
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0711.4903v1 [astro-ph]
Submission history
From: Alessandro Sozzetti [view email]
[v1] Fri, 30 Nov 2007 11:10:12 GMT (42kb)
http://arxiv.org/abs/0711.4903
Double-blind test program for astrometric planet detection with Gaia
Authors: S. Casertano (1), M.G. Lattanzi (2), A. Sozzetti (2,3), A. Spagna (2), S. Jancart (4), R. Morbidelli (2), R. Pannunzio (2), D. Pourbaix (4), D. Queloz (5) ((1) STScI; (2) INAF-Osservatorio Astronomico di Torino; (3) Harvard-Smithsonian CfA; (4) Universite’ Libre de Bruxelles; (5) Geneva Observatory)
(Submitted on 4 Feb 2008)
Abstract: We use detailed simulations of the Gaia observations of synthetic planetary systems and develop and utilize independent software codes in double-blind mode to analyze the data, including statistical tools for planet detection and different algorithms for single and multiple Keplerian orbit fitting that use no a priori knowledge of the true orbital parameters of the systems.
1) Planets with astrometric signatures $\alpha\simeq 3$ times the single-measurement error $\sigma_\psi$ and period $P\leq 5$ yr can be detected reliably, with a very small number of false positives.
2) At twice the detection limit, uncertainties in orbital parameters and masses are typically $15%-20%$.
3) Over 70% of two-planet systems with well-separated periods in the range $0.2\leq P\leq 9$ yr, $2\leq\alpha/\sigma_\psi\leq 50$, and eccentricity $e\leq 0.6$ are correctly identified.
4) Favorable orbital configurations have orbital elements measured to better than 10% accuracy $greater than 90%$ of the time, and the value of the mutual inclination angle determined with uncertainties $\leq 10^{\degr}$.
5) Finally, uncertainties obtained from the fitting procedures are a good estimate of the actual errors. Extrapolating from the present-day statistical properties of the exoplanet sample, the results imply that a Gaia with $\sigma_\psi$ = 8 $\mu$as, in its unbiased and complete magnitude-limited census of planetary systems, will measure several thousand giant planets out to 3-4 AUs from stars within 200 pc, and will characterize hundreds of multiple-planet systems, including meaningful coplanarity tests.
Finally, we put Gaia into context, identifying several areas of planetary-system science in which Gaia can be expected to have a relevant impact, when combined with data coming from other ongoing and future planet search programs.
Comments: 32 pages, 24 figures, 6 tables. Accepted for pubolication in A&A
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0802.0515v1 [astro-ph]
Submission history
From: Alessandro Sozzetti [view email]
[v1] Mon, 4 Feb 2008 21:42:54 GMT (2636kb)
http://arxiv.org/abs/0802.0515
The Gaia Project – technique, performance and status
Authors: Stefan Jordan
(Submitted on 14 Nov 2008)
Abstract: Gaia is a satellite mission of the ESA, aiming at absolute astrometric measurements of about one billion stars (all stars down to 20th magnitude, with unprecedented accuracy.
Additionally, magnitudes and colors will be obtained for all these stars, while radial-velocities and spectral properties will be determined only for bright objects (V<17.5). At 15th magnitude Gaia aims at an angular accuracy of 20 microarcseconds (muas).
This goal can only be reached if the geometry of the telescopes, the detectors, and the pointing of Gaia at each moment (“attitude”) can be inferred from the Gaia measurements itself with muas accuracy.
Comments: six pages, invited talk at the conference “Galactic & Stellar Dynamics in the era of high resolution surveys”, Strasbourg 16-20 March 2008
Subjects: Astrophysics (astro-ph)
Journal reference: Astronomisches Nachrichten, AN 329, 875 (2008)
DOI: 10.1002/asna.200811065
Cite as: arXiv:0811.2345v1 [astro-ph]
Submission history
From: Stefan Jordan [view email]
[v1] Fri, 14 Nov 2008 14:08:17 GMT (2795kb,D)
http://arxiv.org/abs/0811.2345