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Without question, the catalog presented here will become out of date before it is printed.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 signi?cantly 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.