Indian Scientists with the Help of James Webb Telescope Formulate Model To Trace Elusive Exo-Moons 

NASA’s James Webb Space Telescope (JWST), which is touted as the most powerful telescope ever built, was successfully placed in outer space last year in December. And, with the help of this JWST scientists at the Indian Institute of Astrophysics (IIA), Bangalore, have developed a model to trace the so far elusive exomoons – natural satellites that revolve around exoplanets (planets orbiting stars other than the Sun).

So far, five thousand exoplanets — planets orbiting stars other than the Sun, have been discovered by using several ground-based and space telescopes such as Kepler, CoRoT, Spitzer, and Hubble space telescopes. However, the natural satellites or exomoon around any of these planets still remain untraced.

Scientists at the IIA, Bangalore, which is an autonomous institute of the Department of Science and Technology (DST), have demonstrated that the newly launched James Webb Space Telescope (JWST) is sufficiently powerful to detect the transit signal of exomoons in the photometric light curves of moon hosting exoplanets.

Schematic diagram of moon hosting exoplanet and its model photometric transit light curve

Professor Sujan Sengupta and his graduate student Suman Saha have developed an analytical model that uses the radius and orbital properties of the host planet and its moon as parameters to model the photometric transit light curve of moon-hosting exoplanets by incorporating various possible orientations of the moon-planet-star system. 

The co-alignment or non-coalignment of the orbits of the planet and the moon are used as parameters (using two angular parameters), and they can be used to model all the possible orbital alignments for a star-planet-moon system. Using these generic models and the analysis of photometric transit light curves of exoplanets that is being obtained by JWST, a large number of exomoons can be detected in near future. 

According to the researchers, an exo-moon around a gas giant planet like Jupiter in the habitable zone of the host star where temperature is appropriate for water to exist in liquid state may harbour life. Under favourable alignment of moon-planet-star, such exomoon may also be detected by JWST. The research has been accepted for publication in The Astrophysical Journal, which is published by the American Astronomical Society (AAS).