You Can’t See This From Here

The Voyager 2 spacecraft camera captured Neptune and Triton together in crescent phase as it passed by in 1989. This picture of the gas giant and its cloudy moon was taken from behind the planet just after closest approach. It could not have been taken from Earth because Neptune never shows a crescent phase to sunward Earth; the sun always fully illuminates Neptune from our point of view. The unusual vantage point robs Neptune of its familiar blue color because the sunlight seen from behind the planet is scattered forward and is reddened like the setting Sun.

Image Credit: NASA

Miranda

This Voyager 2 color image of the Uranian satellite, Miranda is a composite of three shots taken through green, violet, and ultraviolet filters from the narrow angle camera. It is the best color image of Miranda returned to date. Miranda, just 480 km across, is the smallest of Uranus’ five major satellites. It was taken in 1986 during Voyager 2’s fly of Uranus.

Image Credit: NASA

Looking at Neptune

Neptune-This picture of Neptune was produced from the last whole planet images taken through the green and orange filters on the Voyager 2 narrow angle camera. The images were taken on 31 years ago at a range of about 7 million km, 4 days and 20 hours before closest approach on 25 August, 1989. The picture shows the Great Dark Spot and its companion bright smudge. The fast moving bright feature called “Scooter” and the little dark spot are visible near the western limb. These clouds were seen to persist for as long as Voyager‘s cameras could resolve them. A bright cloud band similar to the south polar streak may be seen to the north.

Six years ago, the New Horizons spacecraft crossed the orbit of Neptune today on its way to Pluto, but Neptune was not nearby. In July,2014, New Horizons took this picture of Neptune from almost 4 billion km away.neptune-triton-7-10-14-new_hoizonsImage Credit: NASA

Neptune, Triton, Rings, and Stars

Neptune-South-Pole-Voyager-2_950x682Voyager 2 took the images used to produce this picture of the Neptunian system as it was outbound from the planet on 25 August, 1989. Cruising through the outer solar system, the Voyager 2 spacecraft made its closest approach to Neptune on August 25, 1989, the only spacecraft to visit the most distant gas giant. The image captures the planet and Triton as thin sunlit crescents. A close look shows cirrus clouds and a dark band circle Neptune’s south polar region, with a cloudy vortex above the pole itself. (Pole is just past 6:30 on the planet in this orientation.) Parts of the very faint ring system that was discovered during the Voyager 2 flyby are also visible. The background starfield is composed from sky survey data centered on the constellation Camelopardalis, corresponding to the outbound Voyager‘s point of view.

Image Credit: NASA

Uranus is Weird

Back 1986, Voyager 2 flew by the planet Uranus and gave us our only set of closeup data so far. Recently, that flyby data has shown us the Uranus is even stranger than we thought.

The planet’s rotational axis is tipped over almost 90 degrees, and the Voyager data has revealed that its magnetic axis points about 60 degrees away from the rotational axis. The planet’s magnetosphere wobbles around, and to date, no one has come up with a reasonable explanation of for the odd offset.

Image Credit: NASA

30 Years Ago

It’s been 30 years since Voyager 2 did it’s last planetary flyby at Neptune. It took his picture  less than five days before the spacecraft’s closest approach 25 August, 1989. The picture shows Neptune’s “Great Dark Spot”—a giant storm—and the bright clouds that follow the storm.

Image Credit: NASA

Jupiter’s Rings

Saturn’s rings are so prominent that they can be seen through a small telescope from Earth, but the other gas giant planets, Jupiter, Uranus, and Neptune, have ring systems as well. Jupiter's Rings

Jupiter’s rings were discovered by Voyager 1 in a single image that was targeted specifically to search for a possible ring system. Voyager 2 was reprogrammed en route to take a more complete set of pictures. The image above is from that series. We now known that the system has three major components. The Main ring is about 7,000 km wide and has an abrupt outer boundary roughly 129,000 km from the center of the planet. This ring encompasses the orbits of two small moons, Adrastea and Metis, which probably are the source for the material that makes up most of the ring. The main ring merges gradually into the Halo on the side toward Jupiter. The halo is a broad, faint, donut of material about 20,000 km thick and extending halfway from the main ring down to the planet’s cloudtops.

Around the main ring is the broad and exceedingly faint Gossamer ring. It extends out beyond the orbit of the moon Amalthea and is probably composed of dust particles less than 10 µm in diameter. That’s roughly the size of cigarette smoke particles. It extends to an outer edge of about 129,000 km from the center of the planet and inward to about 30,000 km. The origin of the ring is probably material knocked loose by micrometeorite bombardment of the tiny moons orbiting within the ring.

Jupiter’s rings and moons exist within an intense radiation belt of electrons and ions trapped in the planet’s magnetic field. These particles and fields make up the Jovian magnetosphere or magnetic environment which extends up to 7 million km toward the Sun and stretches outward 750 million km in a windsock shape to Saturn’s orbit.

Image Credit: NASA

Titania

titania3_voyg2Titania’s tortured terrain is a mix of valleys and craters. Voyager 2 passed this moon of Uranus in 1986 and took this photograph. The long valleys indicate that Titania underwent some unknown tumultuous resurfacing event in its distant past. Titania is essentially a large dirty iceball composed of a roughly 50/50 mix of water ice and rock. It was discovered by William Hershel in 1787.

Image Credit: NASA

Two Views of Uranus

natural and false colorThese two pictures of Uranus—one in true color (left) and the other in false color—were compiled from images returned in 1986 from the narrow-angle camera of Voyager 2. The spacecraft was 9.1 million kilometers from the planet, several days from closest approach.

The picture on the left has been processed to show Uranus as human eyes would see it. It was assembled from images taken through blue, green, and orange filters. The darker shadings at the upper right of the disk correspond to the day-night boundary on the planet. The night side of the planet northern hemisphere of Uranus. (“Hold it,” I hear the Gentle Reader cry. “Shouldn’t the half of the northern hemisphere be in daylight.” No. Not on Uranus. The planet’s axis is tilted almost 90°.) The blue-green color results from the absorption of red light by methane gas in the planets deep, cold, and remarkably clear atmosphere.

The picture on the right uses false color and extreme contrast enhancement to bring out subtle details in the south polar region of Uranus. It uses images take through ultraviolet, violet, and orange filters shifted to the same blue, green, and red colors used to produce the picture at left. The very slight contrasts visible in true color are greatly exaggerated. The false color image reveals a dark polar hood surrounded by a series of progressively lighter concentric bands. One possible explanation is that smog, concentrated over the pole, is arranged into bands by zonal winds of the upper atmosphere. The bright orange and yellow strip at the edge of the planet’s limb is an artifact of the image enhancement.

Image Credit: NASA

Neptune

Neptune-This picture of Neptune was produced from the last whole planet images taken through the green and orange filters on the Voyager 2 narrow angle camera. The images were taken on 25 years ago at a range of about 7 million km, 4 days and 20 hours before closest approach on 25 August, 1989. The picture shows the Great Dark Spot and its companion bright smudge. The fast moving bright feature called “Scooter” and the little dark spot are visible near the western limb. These clouds were seen to persist for as long as Voyager‘s cameras could resolve them. A bright cloud band similar to the south polar streak may be seen to the north.

Image Credit: NASA

UPDATE—The New Horizons spacecraft crossed the orbit of Neptune today on its way to Pluto. Neptune was not nearby. In July, New Horizons took this picture of Neptune from almost 4 billion km away.neptune-triton-7-10-14-new_hoizonsImage Credit: NASA

Neptune, Triton, Rings, and Stars

Neptune-South-Pole-Voyager-2_950x682Voyager 2 took the images used to produce this picture of the Neptunian system as it was outbound from the planet on 25 August, 1989. Cruising through the outer solar system, the Voyager 2 spacecraft made its closest approach to Neptune on August 25, 1989, the only spacecraft to visit the most distant gas giant. The image captures the planet and Triton as thin sunlit crescents. A close look shows cirrus clouds and a dark band circle Neptune’s south polar region, with a cloudy vortex above the pole itself. (Pole is just past 6:30 on the planet in this orientation.) Parts of the very faint ring system that was discovered during the Voyager 2 flyby are also visible. The background starfield is composed from sky survey data centered on the constellation Camelopardalis, corresponding to the outbound Voyager‘s point of view.

Image Credit: NASA

Jupiter’s Rings

Saturn’s rings are so prominent that they can be seen through a small telescope from Earth, but the other gas giant planets, Jupiter, Uranus, and Neptune, have ring systems as well. Jupiter's Rings

Jupiter’s rings were discovered by Voyager 1 in a single image that was targeted specifically to search for a possible ring system. Voyager 2 was reprogrammed en route to take a more complete set of pictures. The image above is from that series. We now known that the system has three major components. The Main ring is about 7,000 km wide and has an abrupt outer boundary roughly 129,000 km from the center of the planet. This ring encompasses the orbits of two small moons, Adrastea and Metis, which probably are the source for the material that makes up most of the ring. The main ring merges gradually into the Halo on the side toward Jupiter. The halo is a broad, faint, donut of material about 20,000 km thick and extending halfway from the main ring down to the planet’s cloudtops.

Around the main ring is the broad and exceedingly faint Gossamer ring. It extends out beyond the orbit of the moon Amalthea and is probably composed of dust particles less than 10 µm in diameter. That’s roughly the size of cigarette smoke particles. It extends to an outer edge of about 129,000 km from the center of the planet and inward to about 30,000 km. The origin of the ring is probably material knocked loose by micrometeorite bombardment of the tiny moons orbiting within the ring.

Jupiter’s rings and moons exist within an intense radiation belt of electrons and ions trapped in the planet’s magnetic field. These particles and fields make up the Jovian magnetosphere or magnetic environment which extends up to 7 million km toward the Sun and stretches outward 750 million km in a windsock shape to Saturn’s orbit.

Image Credit: NASA

Giant Spotted Planets

jupiter_red_spotOne of the most recognizable features in the Solar System is Jupiter’s Red Spot. However, Jupiter is not the only spotted planet. Neptune has long-term storm systems known as the dark spots. Voyager 2 made a close up picture of a Great Dark Spot when it flew by Neptune in 1989.

Based on observations taken by Voyager and with the Hubble Space Telescope, Neptune appears to have a Great Dark Spot more often than not. The Great Dark Spot is thought to be a hole in the methane cloud deck of Neptune. nepture_dark spot.

Neptune’s Great Dark Spot generates large white clouds at or just below the tropopause layer of the planet’s atmosphere similar to high-altitude cirrus clouds found on Earth. However, Neptune’s cirrus clouds are made up of crystals of frozen methane instead of water ice.

Image Credits: NASA