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Hubble Space Telescope WFPC2

Description of Neptune Color Image Pair:

These two images provide views of weather on opposite hemispheres of Neptune on 13 August 1996. They are derived from Wide Field Planetary Camera 2 images made with the Hubble Space Telescope during nine orbits spanning one 16.11-hour rotation of Neptune. Images at 0.467 um (blue), 0.673 um (red), and greater than 0.85 um (near infrared, and not visible to the human eye) were assigned to blue, green, and red colors respectively in making the color composites. To avoid color fringing due to planet rotation between successive images, each image was interpolated to a fixed time from images at adjacent times. The 0.467um and 0.673 um images were also processed to remove limb-darkening. In these composite color images, as in true color images, the predominant blue color comes from the absorption of red and infrared light by methane gas. Clouds elevated above most of the methane absorption appear white, while the very highest clouds tend to be yellow-red, as seen in the bright feature at the top of the right hand image (35 deg N latitude). The dark blue band in the middle of both images is just south of Neptune's equator where wind speeds reach almost 900 mph, blowing opposite to the eastward rotation of the planet. The bright white clouds are at a latitude of 45 deg S, where winds are only 10% as strong. The green band, extending between 55 deg S and 65 deg S, arises from local excess absorption at blue wavelengths, for currently unknown reasons.


Our HST and Ground Based images of Neptune (click to enlarge):

Montage of images of Neptune acquired in filtered light (ultraviole to red) from HST on 8 November 1996.  The filter is identified below each image - the three digits associated with each filter name indicate the central wavelength of the band that the filter lets through, and the suffix (W, N or M) indicates the bandpass for that filter, Wide, Narrow or Medium, respectively.
 
 

 
Montage of images of Neptune in the infrared region of the spectrum, obtained nearly simultaneously from the HSt and the NASA/Infrared Telescope Facility in
Hawaii.




The cylindrical maps above show the global appearance of Neptune in 1996 at "blue" (467 nm) and near infrared (673 nm).


Credits:

The digital images produced at the University of Wisconsin-Madison, Space Science and Engineering Center (SSEC), 1225 W. Dayton St. Images were obtained from observations with the Hubble Space Telescope. The science team is headed by Larry Sromovsky at the University of Wisconsin, other team members are Sanjay Limaye and Pat Fry (SSEC), Kevin Baines and Glenn Orton (JPL), and Andrew Ingersoll (Cal Tech).


View the MPEG Movie of Neptune!

Description of the SSEC Neptune Movie:

PART 1.

Groundbased Image. The first image presented in the movie is a color composite of images made from the NASA Infrared Telescope Facility at the top of Mauna Kea, a 14,000 ft volcanic mountain on the big island of Hawaii. The three component images were all made at near infrared wavelengths not visible to the human eye, and also not visible to the camera on the Hubble Space Telescope. The blue component of this image is made with a 1.26 um filter (a wavelength at which methane absorbs), the green with a 2 um filter, and the red with a 2.1 um filter (a wavelength at where there is strong absorption by hydrogen gas, the main component of Neptune's atmosphere). These different wavelengths provide important clues regarding the vertical location and structure of the clouds. Dense, high clouds will appear bright in all three colors. But low level clouds can only appear bright in the blue component. A very high diffuse cloud might be seen only in the red image, as seen at the upper left. The ground-based image is fuzzy because small density variations in the atmosphere above the telescope causes distortions, much like air above a hot pavement. Because Neptune is so far away from the sun (30 times further than the earth) its angular extent is very small (2.3 arc seconds, or about one sixteen hundredth of a degree). Even under exceptionally good conditions present when these images were taken, the atmosphere limits groundbased telescopes to angular resolutions of about 0.5 arc seconds, about 1/5 of Neptune's diameter. From its vantage point in space, the Hubble Space Telescope's vision is unaffected by atmospheric density variations.

PART 2.

Dissolve to Hubble Image. The groundbased image dissolves into the Hubble Space Telescope image made at the same time as the groundbased image. This and the following images provide views of Neptune's weather on 13-14 August 1996. They are derived from Wide Field Planetary Camera 2 images made with the Hubble Space Telescope during nine orbits spanning one 16.11-hour rotation of Neptune. Images at 0.467 um (blue), 0.673 um (red), and greater than 0.85 um (near infrared, and not visible to the human eye) were assigned to blue, green, and red colors respectively in making the color composites. To avoid color fringing due to planet rotation between successive images, each image was interpolated to a fixed time from images at adjacent times. The 0.467um and 0.673 um images were also processed to remove limb-darkening. In these composite color images, as in true color images, the predominant blue color comes from the absorption of red and infrared light by methane gas. Clouds elevated above most of the methane absorption appear white, while the very highest clouds tend to be yellow-red, as seen in the bright feature at the top of the right hand image (35 deg N latitude). The dark blue band in the middle of both images is just south of Neptune's equator where wind speeds reach almost 900 mph, blowing opposite to the eastward rotation of the planet. The bright white clouds are at a latitude of 45 deg S, where winds are only 10% as strong. The green band, extending between 55 deg S and 65 deg S, arises from local excess absorption at blue wavelengths, for currently unknown reasons.

PART 3.

Rotation Movie. The rotation of Neptune is shown greatly accelerated from its normal 16.11 hour period. At the start of the movie a bright orange cloud is shown at the upper right edge of the image, this subsequently rotates around the backside of the planet and eventually is seen again near the central meridian. Small cloud features are seen at a variety of latitudes. These will be used with the larger ones to trace Neptune's circulation pattern. At least one cloud can be seen to dissipate before completing its transit across the visible disk. At 45 deg S there are two bright white clouds on opposite sides of the planet. No great dark spot can be seen in the southern hemisphere; the dominant earth-sized storm seen during the 1989 Voyager encounter apparently dissipated in 1990. The last image is overlaid with a latitude-longitude grid of 30 deg spacing.
 

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