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Update from the DC Planet Search

March 6th, 2006 1 comment

Winter continues to trudge toward conclusion at the Naval Observatory in the heart of Washington DC. Despite the odd blizzard, the weather – and the equipment in USNO’s 24-inch dome – has cooperated fairly well so far in 2006. We’ve also been fortunate to add a new observer to our team. Zach Dugan is a Junior astronomy major at Yale (and a DC resident during school breaks). At the moment, Zach is taking a semester Down Under, at the University of Melbourne, but he will rejoin us in a few months. The Naval Academy also finalized an indefinite loan of a liquid nitrogen-cooled ccd camera to USNO, making the search for exoplanet transits a much-improved operation, and certainly less of a headache for observer and USNA Senior John Pepin. We have endured two camera failures, light pollution challenges, and pointing difficulties (owing to 1970’s vintage – read slipping — analog sidereal time dials) in his quest to detect transits. Nevertheless, he got a chance to present initial results with a poster at the January AAS Meeting.

USNO in the SNO

Our recent transit searches have focused on two interesting planetary systems. The first, HD 80606, has been an elusive, and long-running target for the collaboration. The parent star, HD 80606A is a relatively ordinary metal-rich solar-type star in a wide binary. It harbors a planet with an absolutely crazy orbit: P=111.4 days, e=0.935. (Have a go at fitting it with the Systemic Console.) In the figure below, we plot its position at daily intervals, with the orbits of Earth, Venus, and Mercury shown for comparison:

orbital figure of HD 80606 b
HD 80606 b likely has some of the worst weather in the Galaxy, and hence we would learn an extraordinary amount from follow-up observations if it were found to transit. Although the planet regularly whips down within 6 stellar radii of the stellar surface, the orientation of the orbit is not particularly well suited for possible occultations, and the a-priori transit probability is a slim 1.7%.

The most recent transit detection opportunity occurred in a 3-sigma window that covered about a day to either side of Jan. 26th. We met the window at the ready with the USNO 24-inch, but the weather was largely uncooperative, and we were clouded out on both the 25th and 26th. We were, however, able to obtain observations throughout the evening of the 27th. No transit was observed. The non-detection rules out some of the allowed parameter space, and thus makes our task slightly easier during the next transit opportunity on May 17th. Mark your calendars!

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