On February 29, 2004, Donald C. Parker of Coral Gables, Florida, acquired a series of seven CCD images showing the very large, diffuse blue feature currently visible in Jupiter's South Equatorial Belt (south is up). The feature is highlighted in the center view, acquired at 5:36 Universal Time on the 29th; the other images were taken at 5:19 (left) and 6:04 (right). Click on the photo to see the complete image set.
Courtesy Don Parker.
An unusual disturbance has appeared on Jupiter at the interface of the South Equatorial Belt (SEB) and the Equatorial Zone (EZ). It's visible as a very elongated bluish feature, highlighted in the center image above. The feature's bluish hue is more pronounced when it's near Jupiter's limb but is quite subtle when crossing the central meridian.
This disturbance was first detected on February 26, 2004, by European amateurs. On the 29th the new feature was some 40° long (in longitude) and was transiting Jupiter's central meridian about 2.5 hours before the Great Red Spot (GRS). Based on this estimate, you can use our GRS calculator to determine the approximate transit times of this disturbance on the next few nights. The time difference between the new feature and the GRS will increase slowly because features in Jupiter's EZ rotate slightly faster than the GRS.
Almost any kind of Jupiter observation requires familiarity with the correct names for the various belts and zones. This diagram replicates the view in an inverting telescope such as a Newtonian reflector, or a refractor, Schmidt-Cassegrain, or Maksutov used without a star diagonal. Telescopes used with a star diagonal will have north up but east and west reversed. The planet's rotation causes features to move from east (following) to west (preceding). Click on the image for a larger view.
Sky & Telescope illustration.