Evolution Of The Oval Ba During 2004-2005

During 1939-41, dark features appeared in the South Tropical Zone, and in between these features the 3 Great South Temperate Belt White Ovals, designated as BC, DE and FA, emerged (The Giant Planet Jupiter, J. Rogers p.223). The ovals were elongated, like the Great Red Spot (GRS), with an aspect ratio (major/minor axis) of about 2. The ovals merged in 1998-2000 into White Oval BA, and this oval was much rounder than its predecessors, with an aspect ratio of 1.3. Since 2000 the Oval has been observed regularly from the ground by amateur astronomers, using equipment that provided diffraction-limited images of Jupiter. These images reveal major changes in the Oval BA. During the last conjunction between the Oval BA and the GRS, in 2004, the Oval BA became more elongated for a brief period of time. During the 2005 apparition of Jupiter, features were observed inside the Oval BA.

These changes culminated in December 2005 when the Oval BA turned red (between December 1-9), the same shade of red as the GRS. Methane band images (892nm) showed that the Oval BA, like the GRS, is bright. This filter signifies high altitude clouds. Amateur images along with Hubble Space Telescope images further showed the formation of a red ring inside Oval BA. Another conjunction between the Oval BA and the GRS is currently on going. As in 2004, the Oval BA is now more elongated. In this poster we will show a compilation of images taken between 2004 and 2006, highlighting the changes that have occurred in Oval BA throughout conjunction in July 2006. Amateur images, alongside HST observations from April 2006, and Keck adaptive optics images from 21 July 2006 (UT) will be shown.