It is Astrophoto Friday! This week's image shows a unique event that was captured by the 200-inch Hale Telescope armed with adaptive optics.
What might look like Pac Man swallowing a dot is actually Saturn's moon Titan occulting (passing in front of) a binary star system (named NV0435215+200905). The two stars are separated in the sky by just 1.5 arc seconds (One arc second is 1/3600 of a degree).
Because fantastic resolving power of the Hale using adaptive optics you can see that the light of the star nearest to Titan is being refracted by Titan's dense atmosphere. Such events are rare, but valuable. The starlight as it is seen passing through Titan's atmosphere is essentially a probe providing clues as to the density, temperature and wind patterns of this distant world. The team of astronomers (Antonin Bouchez, Michael E. Brown, Mitchell Troy, Rick S. Burruss, Richard G. Dekany and Robert A. West) that observed this event December 20, 2001 was fortunate that both of the stars were seen to pass behind Titan. This provided two passes through Titan's atmosphere - effectively doubling what could be learned from the event.
Be sure to check out the movie of the event. As you watch it will look like Titan is still and the stars are moving behind it. As they pass behind Titan be sure to look for the refracted light of each star on either side of Titan's atmosphere. It is an impressive sight!
The result? Jet stream winds were discovered in Titan's atmosphere.
For those so inclined you can read a pdf of one of the scientific publication that came out of these observations.