The search for other worlds in the galaxy took a giant step about 20 years ago, with the discovery of a 1st planet orbiting a star other than the Sun. It was named 51 Peg b (Mayor and Queloz 1995). This discovery gave birth to a new field of research: exoplanetology, with the goal of determining the prevalence, diversity and origins of planetary systems. Since then, searching for and characterizing exoplanets has become one of the most active fields in astronomy. Today we know of several thousand exoplanets.
Most of the exoplanets known to date were discovered indirectly, by observing the reflex orbital motion of the host star, by means of precise measurement of variations in the star’s radial velocity (also known as the RV method), or of the reduction in the flux of a host star when a planet passes in front of it once every orbit (transit method). Improvements in the precision of RV measurements over the years has led to the discovery of progressively less massive planets, and super-Earths (~ 2-10 Earth masses) have now been found in some systems (Mayor et al. 2011). Similarly, the many advances in transit observations have made it possible to detect hundreds and hundreds of exoplanets, some of them as small as Earth (Borucki et al. 2011).
The success of the transit technique suggests a very exciting possibility: the detection of exomoons by measuring transit timing variation (TTV) and transit duration variation (TDV). Detecting a moon around an exoplanet would be a world first and would have an enormous impact on our understanding of planet and satellite formation and the dynamic evolution of planetary systems. Moreover, detecting a giant planet in the habitable zone of its star would improve our understanding of the origins and prevalence of life in the universe. If the exomoon is massive enough to hold an atmosphere (> 0.1 to 0.2 Earth mass), it could be a good environment for the development of life (Williams et al., 1997).
Aside from exomoons, transit timing can also lead to the discovery of other planets in systems already known to have 1 planet (Holman and Murray, 2005, Agol et al. 2005). This would allow us to extend the survey of multi-planet systems and to obtain better statistics on the relative configuration and properties of planets in these systems. The TTV method is sensitive to very low-mass planets, of 1 Earth mass or less. This means it fits perfectly with the radial velocity method, which is generally limited to larger masses.
To carry out this project we are currently developing an entirely new camera, called PESTO (extra-solar planets in transit and occultation, in French), fully optimized for the timing of exoplanet transits. This work was made possible thanks to a grant from the CFI to the lead researcher, Professor David Lafrenière. The camera will be used with the 1.6 m telescope at the Observatoire du Mont-Mégantic, which is powerful enough to reach the required photometric limits.
The new camera, working in the red part of the optical spectrum and based on a high-speed CCD detector (L3 EMCCD), will feature a very high signal sampling rate (~10-100 Hz), zero readout noise and no dead time between images, absolute millisecond time-stamping data thanks to a GPS system, a feedback mechanism for stabilizing the telescope direction and focus, and a field of vision allowing the user to observe several reference stars simultaneously so as to calibrate systematic effects. It will also have functionalities for reducing the signal induced by atmospheric scintillation, on the principle developed by Osborn et al. 2011.
All these characteristics mean that the PESTO camera will offer excellent photometric precision with a high sampling rate, making it optimal for TTV and TDV measurements. No other camera with all these features exists as yet.