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Headshot of Emily Lakdawalla

Lesser-known views of Uranus and Neptune

Posted by Emily Lakdawalla

28-05-2013 10:58 CDT

Topics: Hubble Space Telescope, pretty pictures, amateur image processing, Voyager 1 and 2, Neptune, Uranus

Today I needed to come up with a list of great and unusual Neptune and Uranus photos to recommend to another space writer, and I figured that the best way to go about that was to write a blog entry!

I claim that despite the fact that Voyager 2 returned relatively few high-resolution images from either of those worlds, there are many more photos in the archives than regularly make it to public view. You can visit JPL's Planetary Photojournal to see all of these -- 48 press-released photos for Uranus and its moons, and 74 for Neptune and its moons. These contain classics such as this ultramarine-blue Neptune with its great dark spot and this much paler Uranus and its freakishly exaggerated "bull's eye" version. Together, those two images have resulted in the common depiction of Uranus as much lighter or paler (and often, as in this version by Calvin Hamilton, greener) than Neptune.

In fact, though, the two ice giants are near-twins, which you can see if you compare these two versions by Icelandic amateur image processor Björn Jónsson. At the time that Voyager 2 flew past, Uranus was grayer and less feature-rich than Neptune, but both shared the same serene methane-blue color.

Color global view of Uranus from Voyager 2

NASA / JPL / Björn Jónsson

Color global view of Uranus from Voyager 2
The images for this color composite of Uranus were obtained by Voyager 2 through orange, green, and blue filters on January 14, 1986 from a range of 12.6 million kilometers. The color has been adjusted to approximate what a human eye would see, although the human eye is sensitive to longer wavelengths of light than the Voyager cameras were.
Neptune from Voyager

NASA / JPL / color processing by Björn Jónsson

Neptune from Voyager
This new view of Neptune was created from images captured by Voyager 2 as it approached the planet at a range of more than 10 million kilometers on August 17, 1989. It was processed to present Neptune in approximately true color. The processing was complicated by the fact that 18 minutes separated the acquisition of orange, green, and violet frames, since Voyager 2 was transmitting data back to Earth in real time, and bit rates were very low at Neptune's distance from Earth.

If you look at Uranus now, though, it's much more exciting than it was then. With its passage through equinox, the Sun is striking the whole planet, and its sky has erupted with bands and storms. Neptune has not remained constant, either. It's tempting to think of Neptune's Great Dark Spot as being something like Jupiter's Great Red Spot, but in fact the Dark Spot has disappeared since Voyager 2's encounter. Smaller versions of it have come and gone. Croatian amateur Gordan Ugarkovic has worked with Hubble data to see Neptune's changed face, while Heidi Hammel's work on her own data shows Uranus sporting dark spots of its own.

Neptune from Hubble, August 28, 2010

NASA / STScI / Kathy Rages / Gordan Ugarkovic

Neptune from Hubble, August 28, 2010
The new Wide Field Camera 3 on Hubble was employed to photograph Neptune in near-natural color on August 28, 2010, when the planet was near its opposition. The version on the right has enhanced contrast, revealing a dark ring of clouds around the south pole. Triton would be visible to Hubble if it were in the frame, but it was not in the camera field of view at the time of the observation.
New dark spot on Uranus

NASA, ESA, L. Sromovsky and P. Fry (University of Wisconsin), H. Hammel (Space Science Institute), and K. Rages (SETI Institute)

New dark spot on Uranus
As Uranus approached its equinox on December 7, 2007, the planet's storm activity was heating up. Each day exposed more of its northern hemisphere to sunlight for the first time in decades. The Hubble Space Telescope targeted Uranus on August 24, 2006, capturing this view of new dark spots in the northern hemisphere.

The two planets also look quite similar seen from behind. These are views possible only from a spacecraft, the like of which I don't know whether I'll ever see again. Only if we manage to get orbital missions (or perhaps another flyby) launched to either of these two distant worlds. I love this crescent planet data and processed the versions below.

Uranus' crescent, February 1, 1986

NASA / JPL / Emily Lakdawalla

Uranus' crescent, February 1, 1986
A week after its flyby, Voyager 2 still had a high-resolution view of Uranus' receding crescent using its narrow-angle camera.
Crescent Neptune and Triton

NASA / JPL / Emily Lakdawalla

Crescent Neptune and Triton
Neptune was the last planet Voyager 2 passed. As it departed the system in September 1989, it watched the crescent planet (along with its largest moon) diminish. This photo was taken on September 3, about 9 days after the flyby.

And finally, both planets have rewarded smart and sharp-eyed amateurs seeking new details in old data. Here's one of my favorite such stories, about American amateur Ted Stryk's hunt for transiting moons in the Voyager 2 Neptune data set. Here's one of the pictures from that story:

Despina eclipses and transits Neptune (Despina brightened)

NASA / JPL / Ted Stryk, Roane State CC

Despina eclipses and transits Neptune (Despina brightened)
This view of Despina eclipsing and transiting Neptune is composed of four frames captured nine minutes apart on August 24, 1989 from 20:00 to 20:27 through blue, orange, violet, and green filters. In this version, Despina has been brighted substantially to make it easier to spot.

And here are some images that show Uranus' atmosphere wasn't featureless when Voyager 2 flew past: Czech amateur Daniel Machácek has managed to find clouds buried in the Voyager 2 pixels.

Cloud features revealed in Voyager 2 Uranus images

NASA / JPL / Daniel Macháček

Cloud features revealed in Voyager 2 Uranus images
This is among the highest-resolution of the images that Voyager 2 obtained at Uranus. A few cloud details are visible at a resolution of about 12 kilometers per pixel.
Uranus South Polar Atmospheric Structure

NASA / JPL / Daniel Macháček

Uranus South Polar Atmospheric Structure
Voyager 2's best image of Uranus' south pole, processed to bring out atmospheric structure. The circular feature is real, but some details are not. In particular, nearly horizontal lines are artifacts from flatfielding.

Visit the space images section of this website for more pictures of Uranus and its moons and more pictures of Neptune and its moons.

 
See other posts from May 2013

 

Or read more blog entries about: Hubble Space Telescope, pretty pictures, amateur image processing, Voyager 1 and 2, Neptune, Uranus

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