... Iapetus: Saturn's Disappearing Moon . ... Rhea: Saturn's Second Largest Moon . ... On the cloud tops of Jupiter near the left edge of the picture can be seen a dark circular spot which is caused by the shadow of Jupiter's largest moon Ganymede. HH-47 Star Jet . ... LMC Star Clouds . ... Dark Bok Globules in IC 2944 . ... Bok globules, named after astronomer Bart Bok who studied them extensively, are small dark clouds made of gas and dust that are typically condensing to form a star or stars. ...