Titan Occultation Observing Campaign
Looking for Titan's Central Flash
Periodically the largest moon of Saturn, Titan, occults a bright star in such a way that the centrality of the occultation will be visible from some places on the Earth. When this occurs it is possible to observe an effect known as the central flash. Titan possesses an atmosphere and this acts like a lens focusing the starlight from the occulted star in a manner analogous to gravitational microlensing.
This flash is detected by making photometric measurements and producing a light curve. As Titan passes in front of the star the total amount of light seen from the two objects falls. At the midpoint of the occultation a small peak is observed in the light curve as the refracted starlight is detected.
This flash is a very unique way to measure accurately (to within a couple of km) the shape of Titan's atmospheric isobar near 0.25 mbar, hence giving a very tight constraint on the zonal wind system of the satellite.
Over recent years a number of observations have been made of such an event. On 14 November 2003 two such events occured within 7 hours of each other when Titan occulted the stars TYC 1343-1615-1 and TYC 1343-1865-1. Teams of observers at various locations around the world witnessed the event.