Hard to believe that it’s been over ten years now since the discovery of 51 Peg B, the first exoplanet found around a main sequence star. So much has happened since, including over 160 exoplanet candidates identified within 200 parsecs, with most of these discovered through Doppler search methods examining radial velocities (although the nearby planet TrES-1 was found via transit methods). The last published list of exoplanets appeared in 2002, which is why the just published “Catalog of Nearby Exoplanets” is so welcome.
Appearing in The Astrophysical Journal, the catalog confines itself to the 200 parsec limit for good reasons. Yes, we have located exoplanets far beyond it, including some in the direction of galactic center found by the OGLE survey and several found through microlensing projects elsewhere. But within 200 pc, high resolution imaging and stellar spectroscopy allows satisfactory follow-up work, and we’re also working with stars whose parallax has been studied through the Hipparcos satellite. And as Paul Butler, Geoff Marcy and colleagues note in the paper, nearby host stars are bright enough to allow rich investigation by smaller telescopes, “…permitting careful assessment of velocity jitter, starspots, and possible transits.”
Why produce a catalog in a time of such rapid discovery? From the paper:
Without question, the catalog presented here will become out of date before it is printed. However, this catalog offers many attributes of unique value. First, it contains updated orbital parameters for 90 exoplanets, computed anew from our large database of Doppler measurements of over 1300 stars from the Lick, Anglo-Australian, and Keck Observatories obtained during the past 18, 7, and 8 yr, respectively (Butler et al. 2003; Marcy et al. 2005a). These new orbital parameters significantly supersede the previously quoted orbital parameters in most cases.
The updating is significant because the longer we observe a star using Doppler techniques, the more refined our datasets become. This allows further development of our models of various star systems and may help to reveal new planets within some of them. Refined estimates of stellar mass do their part in sharpening these calculations as well. Astrophysicist Greg Laughlin calls this a blockbuster paper and is using its data to re-examine the star that started it all, 51 Peg, hoping to tease a 51 Peg c out of the radial measurements.
There are five new exoplanets included in the catalog: HD 11964b, HD 66428b, HD 99109b, HD 107148b, and HD 164922b. Data for these detections was collected at the Keck Observatory. We wind up with 172 known exoplanets in the catalog, with this interesting concluding remark: “…the mass distribution increases sharply toward lower masses (roughly as the inverse of the minimum planetary mass) and toward larger orbital distance. Since these regions are where current surveys are most incomplete, this implies that many more low-mass and long-period planets await discovery as Doppler surveys cover a longer time baseline and become more precise.”
Which, of course, is what we are all waiting for. The scientists promise a forthcoming work that will discuss exoplanet candidates that fit this description. The paper is Butler, Wright, Marcy et al., “Catalog of Nearby Exoplanets,” The Astrophysical Journal 646 (20 July 2006), pp. 505-522, with abstract available here. This is an important work, and it seems worth mentioning that self-archiving on researchers’ home pages, a growing trend, would be a helpful way to get around publisher firewalls to make it available to a broader audience.
Here’s a publically-accessible version of the catalogue: http://exoplanets.org/planets.shtml
First rate. Thanks for tracking this down, Andy!
arXiv: 0812.1582
Date: Mon, 8 Dec 2008 22:36:22 GMT (223kb)
Title: Ten New and Updated Multi-planet Systems, and a Survey of Exoplanetary Systems
Authors: J. T. Wright, S. Upadhyay, G. W. Marcy, D. A. Fischer, E. B. Ford, J. A. Johnson
Categories: astro-ph
Comments: ApJ accepted
We present the latest velocities for 10 multi-planet systems, including are-analysis of archival Keck and Lick data, resulting in improved velocities
that supersede our previously published measurements. We derive updated orbital fits for ten Lick and Keck systems, including two systems (HD 11964, HD 183263) for which we provide confirmation of second planets only tentatively identified elsewhere, and two others (HD 187123, and HD 217107) for which we provide a major revision of the outer planet’s orbit.
We compile orbital elements from the literature to generate a catalog of the 28 published multiple-planet systems around stars within 200 pc. From this catalog we find several intriguing patterns emerging: – Including those systems with long-term radial velocity trends, at least 28% of known planetary systems appear to contain multiple planets.
Planets in multiple-planet systems have somewhat smaller eccentricities than single planets. – The distribution of orbital distances of planets in multi-planet systems and single planets are inconsistent:
Single-planet systems show a pile-up at P ~ 3 days and a jump near 1 AU, while multi-planet systems show a more uniform distribution in log-period. In addition, among all planetary systems we find: There may be an emerging, positive correlation between stellar mass and giant-planet semi-major axis.
Exoplanets more massive than Jupiter have eccentricities broadly distributed across 0 < e < 0.5, while lower-mass exoplanets exhibit a distribution peaked near e = 0.
http://arxiv.org/abs/0812.1582 , 223kb
Detection and Characterization of Extrasolar Planets through Doppler Spectroscopy
Authors: A. Eggenberger, S. Udry
(Submitted on 2 Apr 2009)
Abstract: Over 300 extrasolar planets have been found since 1992, showing that planetary systems are common and exhibit an outstanding variety of characteristics. As the number of detections grows and as models of planet formation progress to account for the existence of these new worlds, statistical studies and confrontations of observation with theory allow to progressively unravel the key processes underlying planet formation.
In this chapter we review the dominant contribution of Doppler spectroscopy to the present discoveries and to our general understanding of planetary systems. We also emphasize the synergy of Doppler spectroscopy and transit photometry in characterizing the physical properties of transiting extrasolar planets.
As we will see, Doppler spectroscopy has not reached its limits yet and it will undoubtly play a leading role in the detection and characterization of the first Earth-mass planets.
Comments: 50 pages, 16 figures, to appear in the proceedings of the Les Houches Winter School “Physics and Astrophysics of Planetary Systems” (EDP Sciences: EAS Publications Series)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:0904.0415v1 [astro-ph.EP]
Submission history
From: Anne Eggenberger [view email]
[v1] Thu, 2 Apr 2009 16:19:37 GMT (478kb)
http://arxiv.org/abs/0904.0415