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Departmental Colloquium

M Dwarf Variability: A Barrier to Detecting Rocky Planets?  
Guest Speaker
Dr. Angelle Tanner  
Guest Affiliation
Mississippi State University, Department of Physics and Astronomy  
Guest Affiliation Url  
Inseok Song  
Thursday, October 6, 2011 4:00 pm - 5:00 pm  
Auditorium, Physics 202  

We are on the verge of potentially the most significant scientific discovery of the past century. The detection of a habitable planet around a star in our solar neighborhood. Currently, infrared radial velocity surveys with precisions of 5-10 m/s are marginally sensitive to Earth-mass planets in the habitable zone of late-M dwarfs (RV signatures of > 5 m/s for an Earth around an M9 star).Indeed, M dwarfs are the primary focus of multiple up-coming infrared RV observing programs with new instruments (ESPRESSO on the VLT) and instrument upgrades (NIRSPEC on Keck and CSHELL on the IRTF). However, if our goal is to detect Earth-mass planets in the habitable zone of a solar-type star (an RV signature of 0.1 m/s for a solar-type star), then it will be advantageous for us to determine the intrinsic jitter inherent to each star in order to better design these observationally intensive observing programs. Optical RV planet search programs have shown that, while in many cases stars with indicators of high photospheric activity also have large RV jitter and there are hints that such activity is correlated with stellar spectral type, the known activity indicators do not always predict the degree of jitter for every star. Here we summarize the need for observing programs to focus on the jitter properties of the nearest stars M dwarfs which are prone to large starspot populations and flares. Future ground-based, milli-mag photometry and star spot modeling as well as the statistical results from the Kepler, MOST and Corot missions will provide starspot rotation periods (a few days to weeks) which are directly related to the RV jitter. The results of this study will be used to infer limits to Earth-mass planet detections around solar-type stars an issue which has not been thoroughly addressed observationally despite the critical limit of a precision of 0.1 m/s needed to detect them in the habitable zone.