On May 20, 2008, a deck of clouds over the Pacific Ocean provided an optical display for the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite. The ring-shaped, rainbow-like phenomenon, known as a glory, appears through the length of the center of this image.
The most obvious ring is about 60 kilometers wide in its center; the red and orange wavelengths are most visible. Parts of at least one inner and one outer concentric ring are also visible, however. At the northwest perimeter of the central ring, a faint patch of green hints at the presence of an outer ring. A faint orange oval is nestled in the center of the main ring as well.
A glory is caused by the scattering of sunlight by a cloud made of water droplets that are all roughly the same size. It always appears in the spot directly opposite the Sun, from the perspective of the viewer; imagine a line connecting the Sun, the viewer, and the spot where the glory appears. This spot is called the anti-solar point. Since the anti-solar point is also where the shadow of a viewer would appear, people have observed glories that have the shadow of an airplane, a hot air balloon, or even their own giant shadows in the center. In the case of this image, the Aqua satellite, which orbits more than 700 kilometers above the Earth, is too far away to cast a detectable shadow.
Other interesting features in the scene are the vortices at the upper right of the image. These vortices, known as Von Karman Vortices, appear downwind of islands that perturb the flow of air like a boulder creates an eddy downstream in a river. The large image shows the islands, and farther northeast, part of the Baja California Peninsula.
NASA image created by Jesse Allen, using data provided courtesy of the MODIS Rapid Response team. Caption by Rebecca Lindsey.
- Aqua - MODIS