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Planetary News: Hubble Space Telescope (2005)

The Hubble Space Telescope Makes a Movie Star Out of Neptune

By Emily Lakdawalla
September 1, 2005

With Saturn in the limelight it's easy to forget that the outer solar system contains several other worthy targets. But the Hubble Space Telescope has proven yet again that beautiful images of outer planets can be captured from Earth. The telescope captured images every 4 to 5 hours over the course of approximately one Neptune rotation. Scientists Erich Karkoschka, of the University of Arizona, and Heidi Hammel, of the Space Science Institute, used the set of observations of Neptune and its moons to generate a beautiful QuickTime movie of Neptune spinning and its moons orbiting (1.3 MB).

The movie begins with a view of Neptune as a human would see it, in "natural color." Cloud features on Neptune are barely discernible in visible wavelengths, but begin to spring into view as the color is enhanced. As the movie opens, the view is a wide one. Two moons are visible: outer Triton, a Pluto-sized icy body that orbits Neptune in a retrograde ("backwards") direction, and inner Proteus, a dark and lumpy Mimas-sized moon. As the movie zooms in, three more inner moons (Larissa, Despina, and Galatea) become visible.

Neptune as seen by the Hubble Space Telescope
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Neptune in natural color, with Proteus (top), Larissa (lower right), Despina (middle left) and Galatea (far left). The brightness of the moons has been enhanced to make them more visible. Credit: NASA, ESA, E Karkoschka, and H. Hammel

Here, the natural color view has been enhanced to emphasize subtle color variations.

Neptune in enhanced color
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This view of Neptune represents data taken in "natural color" wavelengths, but the color has been enhanced to emphasize the subtle color variations in Neptune's atmosphere. Credit: NASA, ESA, E Karkoschka, and H. Hammel

Next, the movie shifts to a view in infrared wavelengths at which methane gas is strongly absorbing. Because of the abundance of methane in Neptune's atmosphere, the planet is very dark-colored at these wavelengths. The only regions of bright color are high-altitude clouds. Neptune's moons, which lack methane atmospheres, also appear much brighter at this wavelength.

Neptune in the infrared
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High-altitude clouds swirl across Neptune's middle latitudes in this view from the Hubble Space Telescope. The image is composed of views in infrared wavelengths at which methane gas is a strong absorber. Credit: NASA, ESA, E Karkoschka, and H. Hammel

Download the movie (QuickTime, 1.3 MB)