Brightness temperature of synchronic exoplanets measured by infrared photometry from the ground: Method and perspective

We explore a method to measure the temperature at the surface of “hot Jupiter” type exoplanets by relative photometry in the infrared at around 10 μm in N spectral band. The method is described and validated by numerical simulations. Thermal radiation from an exoplanet and its parent star are analysed. Geometrical configurations of extra-solar planet rotating synchronously around parent star are explored for a feasibility study of the detection. A Jupiter size planet in orbit at 0.025 astronomical unit from Sun-like parent star should have a harmonic signature of up to 0.2% in amplitude with a period of the planets orbital duration. Such a signature is difficult to detect when making absolute measurements, but by differential methods of analyses, and using a radiative transfer model to take into account background sky contribution of the Earth’s atmosphere, this relative accuracy can be reached. Some results of simulations of observation are also presented.