https://doi.org/10.1088/1538-3873/ab5066
Beichman, C., Ygouf, M., Sayson, J. L., Mawet, D., Yung, Y., Choquet, E., Kervella, P., Boccaletti, A., Belikov, R., Lissauer, J. J., Quarles, B., Lagage, P.-O., Dicken, D., Hu, R., Mennesson, B., Ressler, M., Serabyn, E., Krist, J., Bendek, E., Pueyo, L. (2019). Searching for Planets Orbiting ? Cen A with the James Webb Space Telescope. Publications of the Astronomical Society of the Pacific, 132(1007), 015002. https://doi.org/10.1088/1538-3873/ab5066
? Centauri A is the closest solar-type star to the Sun and offers an excellent opportunity to detect the thermal emission of a mature planet heated by its host star. The MIRI coronagraph on the James Webb Space Telescope can search the 13 au (1”2”) region around ? Cen A which is predicted to be stable within the ? Cen AB system. We demonstrate that with reasonable performance of the telescope and instrument, a 20 hr program combining on-target and reference star observations at 15.5 ?m could detect thermal emission from planets as small as ~5 R?. Multiple visits every 36 months would increase the geometrical completeness, provide astrometric confirmation of detected sources, and push the radius limit down to ~3 R?. An exozodiacal cloud only a few times brighter than our own should also be detectable, although a sufficiently bright cloud might obscure any planet present in the system. While current precision radial velocity (PRV) observations set a limit of 50100 M? at 13 au for planets orbiting ? Cen A, there is a broad range of exoplanet radii up to 10 R? consistent with these mass limits. A carefully planned observing sequence along with state-of-the-art post-processing analysis could reject the light from ? Cen A at the level of ~10?5 at 1”2” and minimize the influence of ? Cen B located 7”8” away in the 20222023 timeframe. These space-based observations would complement on-going imaging experiments at shorter wavelengths as well as PRV and astrometric experiments to detect planets dynamically. Planetary demographics suggest that the likelihood of directly imaging a planet whose mass and orbit are consistent with present PRV limits is small, ~5%, and possibly lower if the presence of a binary companion further reduces occurrence rates. However, at a distance of just 1.34 pc, ? Cen A is our closest sibling star and certainly merits close scrutiny.