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AkaSci 🛰️ (akasci@fosstodon.org)'s status on Monday, 26-Aug-2024 07:03:54 JST AkaSci 🛰️

35 years ago, on Aug 25, 1989, the venerable Voyager 2 spacecraft gave humanity the first close look at planet Neptune.
Voyager 2 swung by at 4,950 km alt above the north pole. 5 hours later, it performed a close fly-by of Triton, Neptune's largest moon, passing within ~40,000 km.
V2 discovered previously unknown Neptunian rings, and confirmed 6 new moons - Despina, Galatea, Larissa, Proteus, Naiad and Thalassa.
This picture of Neptune was taken on Aug 22, 1989.
https://www.nasa.gov/solar-system/30-years-ago-voyager-2s-historic-neptune-flyby/
1/n
In conversation Monday, 26-Aug-2024 07:03:54 JST from fosstodon.org permalink
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1. This picture of Neptune was taken by Voyager 2 less than five days before the probe’s closest approach of the planet on Aug. 25, 1989. The picture shows the “Great Dark Spot” — a storm in Neptune’s atmosphere — and the bright, light-blue smudge of clouds that accompanies the storm. Credits: NASA/JPL-Caltech
  https://cdn.fosstodon.org/media_attachments/files/113/024/163/537/519/988/original/08cc17303ad02bd8.png
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  AkaSci 🛰️ (akasci@fosstodon.org)'s status on Monday, 26-Aug-2024 07:03:53 JST AkaSci 🛰️
  in reply to
  
  This Voyager 2 high-res color image of Neptune's clouds was taken 2 hours before closest approach on Aug 25, 1989 from a distance of 157,000 km.
  These clouds were observed at a latitude of 29° north. The linear cloud forms are stretched approx along lines of constant latitude and the sun is toward the lower left.
  The width of the cloud streaks range from 50 to 200 km, and their shadow widths range from 30 to 50 km. Cloud heights appear to be of the order of 50 km.
  https://photojournal.jpl.nasa.gov/catalog/PIA00058
  2/n
  In conversation Monday, 26-Aug-2024 07:03:53 JST permalink
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  1. This Voyager 2 high resolution color image, taken 2 hours before closest approach, provides obvious evidence of vertical relief in Neptune's bright cloud streaks. These clouds were observed at a latitude of 29 degrees north near Neptune's east terminator. The linear cloud forms are stretched approximately along lines of constant latitude and the sun is toward the lower left. The bright sides of the clouds which face the sun are brighter than the surrounding cloud deck because they are more directly exposed to the sun. Shadows can be seen on the side opposite the sun. These shadows are less distinct at short wavelengths (violet filter) and more distinct at long wavelengths (orange filter). This can be understood if the underlying cloud deck on which the shadow is cast is at a relatively great depth, in which case scattering by molecules in the overlying atmosphere will diffuse light into the shadow. Because molecules scatter blue light much more efficiently than red light, the shadows will be darkest at the longest (reddest) wavelengths, and will appear blue under white light illumination. The resolution of this image is 11 kilometers (6.8 miles per pixel) and the range is only 157,000 kilometers (98,000 miles). The width of the cloud streaks range from 50 to 200 kilometers (31 to 124 miles), and their shadow widths range from 30 to 50 kilometers (18 to 31 miles). Cloud heights appear to be of the order of 50 kilometers (31 miles). This corresponds to 2 scale heights.
    https://cdn.fosstodon.org/media_attachments/files/113/024/424/226/878/069/original/7d8705d5db0e41e1.jpg
  Mr. Bill repeated this.
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  AkaSci 🛰️ (akasci@fosstodon.org)'s status on Monday, 26-Aug-2024 07:03:53 JST AkaSci 🛰️
  in reply to
  
  As Voyager 2 swung past Neptune, it turned its camera around and captured the back-lit rings of Neptune on Aug. 26, 1989 from a distance of 280,000 km.
  The 2 images captured the 2 main rings, the inner faint ring at ~42,000 km from the center of Neptune, and the faint band which extends smoothly from the 53,000 km ring to roughly halfway between the two bright rings. Both of these newly discovered rings are broad and much fainter than the two narrow rings.
  https://photojournal.jpl.nasa.gov/catalog/PIA01997
  #Voyager
  3/n
  In conversation Monday, 26-Aug-2024 07:03:53 JST permalink
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  1. These two 591-second exposures of the rings of Neptune were taken with the clear filter by the Voyager 2 wide-angle camera on Aug. 26, 1989 from a distance of 280,000 kilometers (175,000 miles). The two main rings are clearly visible and appear complete over the region imaged. The time between exposures was one hour and 27 minutes. [During this period the bright ring arcs in the outer bright ring were not visible in either picture (they were unfortunately on the opposite side of the planet for each exposure).] Also visible in this image is the inner faint ring at about 42,000 kilometers (25,000 miles) from the center of Neptune, and the faint band which extends smoothly from the 53,000 kilometer (33,000 miles) ring to roughly halfway between the two bright rings. Both of these newly discovered rings are broad and much fainter than the two narrow rings. These long exposure images were taken while the rings were back-lighted by the sun at a phase angle of 135 degrees. This viewing geometry enhances the visibility of dust and allows fainter, dusty parts of the ring to be seen. The bright glare in the center is due to over-exposure of the crescent of Neptune. The two gaps in the upper part of the outer ring in the image on the left are due to blemish removal in the computer processing. Numerous bright stars are evident in the background. Both bright rings have material throughout their entire orbit, and are therefore continuous.
    https://cdn.fosstodon.org/media_attachments/files/113/024/458/287/594/334/original/e38271aff5184d4b.jpg

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