Lowell Observatory Colloquia

M Dwarf Variability: A Barrier to Detecting Rocky Planets?

Angelle Tanner, Miss. State Univ.

USNO, 12 March, 2012 at 2:00 p.m.

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. Here, I'll will motivate the need for observing programs to focus on the jitter properties of nearby M dwarfs - our most populous stellar neighbors which are prone to large starspot populations and flares. Currently, infrared radial velocity (RV) 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). Optical RV planet search programs have shown that, while some stars with indicators for high photospheric activity also have large RV jitter, these indicators do not always predict the degree of observed RV jitter for every star. Ground-based milli-mag photometry from the Mearth program and high-spectral resolution triage surveys of all nearby stars are necessary to provide the rotational periods and/or vsini measurements that are directly related to the RV jitter. More intense sub-milli-mag photometric studies of a sub-sample of RV planet search targets could reveal whether photometric programs on small telescopes can help find the best stars for terrestrial RV planet search programs. If our goal is to detect Earth-mass planets in the habitable zone of nearby solar-type stars (an RV signature of 0.1 m/s), then it will be advantageous for us to determine the rotational velocity and jitter properties of all such potential targets to better design the observationally intensive observing programs that will be required. What we learn from the M dwarfs can help us find Earths in the habitable zones of nearby solar-type stars.

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