Neptune

During August 16 and 17, 1989, the Voyager 2 narrow-angle camera was used to photograph Neptune almost continuously, recording approximately two and one-half rotations of the planet. These images represent the most complete set of full disk Neptune images that the spacecraft will acquire. This picture from the sequence shows two of the four cloud features which have been tracked by the Voyager cameras during the past two months. The large dark oval near the western limb (the left edge) is at a latitude of 22 degrees south and circuits Neptune every 18.3 hours. The bright clouds immediately to the south and east of this oval are seen to substantially change their appearances in periods as short as four hours. The second dark spot, at 54 degrees south latitude near the terminator (lower right edge), circuits Neptune every 16.1 hours. This image has been processed to enhance the visibility of small features, at some sacrifice of color fidelity.

Image credit: NASA/JPL

Note: For more information, see NASA Pluto-Bound Spacecraft Crosses Neptune's Orbit, 25 Years After Neptune: Reflections on Voyager, and New Horizons Crosses the Orbit of Neptune.

Voyager 2 Flyby of Triton

NASA's Voyager 2 spacecraft gave humanity its first glimpse of Neptune and its moon Triton in the summer of 1989. Like an old film, Voyager's historic footage of Triton has been "restored" and used to construct the best-ever global color map of that strange moon (See PIA18668). The map, produced by Dr. Paul Schenk, a scientist at the Lunar and Planetary Institute in Houston, has also been used to make this movie recreating that historic Voyager encounter, which took place 25 years ago, on August 25, 1989.

Video credit: NASA/JPL-Caltech/Lunar & Planetary Institute

Note: For more information, see PIA18668: Map of Triton and Voyager Map Details Neptune's Strange Moon Triton.

Neptune's New Moon, S/2004 N1

NASA's Hubble Space Telescope has discovered a new moon orbiting the distant blue-green planet Neptune, the 14th known to be circling the giant planet.

The moon, designated S/2004 N 1, is estimated to be no more than 12 miles across, making it the smallest known moon in the Neptunian system. It is so small and dim that it is roughly 100 million times fainter than the faintest star that can be seen with the naked eye. It even escaped detection by NASA's Voyager 2 spacecraft, which flew past Neptune in 1989 and surveyed the planet's system of moons and rings.

Mark Showalter of the SETI Institute in Mountain View, California, found the moon July 1, while studying the faint arcs, or segments of rings, around Neptune. "The moons and arcs orbit very quickly, so we had to devise a way to follow their motion in order to bring out the details of the system," he said. "It's the same reason a sports photographer tracks a running athlete -- the athlete stays in focus, but the background blurs."

The method involved tracking the movement of a white dot that appears over and over again in more than 150 archival Neptune photographs taken by Hubble from 2004 to 2009.

On a whim, Showalter looked far beyond the ring segments and noticed the white dot about 65,400 miles from Neptune, located between the orbits of the Neptunian moons Larissa and Proteus. The dot is S/2004 N 1. Showalter plotted a circular orbit for the moon, which completes one revolution around Neptune every 23 hours.

For images, video, and more information Neptune's new moon, visit: http://hubblesite.org/news/2013/30

Image credit: NASA, ESA, M. Showalter/SETI Institute

How Would the Solar System Look to Aliens?

Dust in the Kuiper Belt, the cold-storage zone that includes Pluto, creates a faint infrared disk potentially visible to alien astronomers looking for planets around the Sun. Neptune's gravitational imprint on the dust is detectable in new simulations of how this dust moves through the solar system. The simulations show how the distant view of the solar system might have changed over its history.

Video credit: NASA; text credit: NASA

One Day on Neptune

On July 12, 2011 Neptune has arrived at the same location in space where it was discovered nearly 165 years ago. To commemorate the event, NASA's Hubble Space Telescope has taken these "anniversary pictures" of the blue-green giant planet.

Neptune is the most distant major planet in our solar system. German astronomer Johann Galle discovered the planet on September 23, 1846. At the time, the discovery doubled the size of the known solar system. The planet is 2.8 billion miles (4.5 billion kilometers) from the Sun, 30 times farther than Earth. Under the Sun's weak pull at that distance, Neptune plods along in its huge orbit, slowly completing one revolution approximately every 165 years.

These four Hubble images of Neptune were taken with the Wide Field Camera 3 on June 25-26, during the planet's 16-hour rotation. The snapshots were taken at roughly four-hour intervals, offering a full view of the planet. The images reveal high-altitude clouds in the northern and southern hemispheres. The clouds are composed of methane ice crystals.

Photo credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

Note: For more information, see Neptune Completes Its First Circuit Around The Sun Since Its Discovery.

Flight over Triton

This simulated voyage over the surface of Neptune's large moon Triton was produced using topographic maps derived from images acquired by NASA's Voyager spacecraft during its August 1989 flyby, 20 years ago.

Triton was the last solid object visited by the Voyager 2 spacecraft on its epic 10-year tour of the outer solar system. Voyager mapped only the hemisphere that faces Neptune, but revealed a very young surface scarred by rising blobs of ice (diapirs), faults, and volcanic pits and lava flows composed of water and other ices. The video begins near the western edge of this hemisphere with an approach over cantaloupe terrain and two large smooth walled plains. The video tracks due east for roughly 1500 kilometers over a large province of volcanic pits, calderas and smooth plains. As can be seen in this video, Triton is locally very rugged (with pits and mounds that are typically a few hundred meters [several hundred feet] high), but has no large mountains or deep basins and regional relief is low. The lack of large topographic features is a consequence of Triton's high internal heat and the low strength of most ices.

The video was produced by using a new topographic map of Triton, combined with a 1.65-kilometer resolution image mosaic. Topographic mapping was based on shape-from-shading analysis of the original Voyager images. Vertical relief has been exaggerated by a factor of 25 to aid interpretation.

Video credit: NASA/JPL/Universities Space Research Association/Lunar & Planetary Institute

Voyager 2 at 12,000 Days

NASA's plucky Voyager 2 spacecraft has hit a long-haul operations milestone today (June 28) -- operating continuously for 12,000 days. For nearly 33 years, the venerable spacecraft has been returning data about the giant outer planets, and the characteristics and interaction of solar wind between and beyond the planets. Among its many findings, Voyager 2 discovered Neptune's Great Dark Spot and its 450-meter-per-second (1,000-mph) winds.

The two Voyager spacecraft have been the longest continuously operating spacecraft in deep space. Voyager 2 launched on August 20, 1977, when Jimmy Carter was president. Voyager 1 launched about two weeks later on September 5. The two spacecraft are the most distant human-made objects, out at the edge of the heliosphere -- the bubble the sun creates around the solar system. Mission managers expect Voyager 1 to leave our solar system and enter interstellar space in the next five years or so, with Voyager 2 on track to enter interstellar space shortly after that.

Having traveled more than 21 billion kilometers (13 billion miles) on its winding path through the planets toward interstellar space, the spacecraft is now nearly 14 billion kilometers (9 billion miles) from the sun. A signal from the ground, traveling at the speed of light, takes about 12.8 hours one-way to reach Voyager 2.

Voyager 1 will reach this 12,000-day milestone on July 13, 2010 after traveling more than 22 billion kilometers (14 billion miles). Voyager 1 is currently more than 17 billion kilometers (11 billion miles) from the sun.

Image Credit: NASA/JPL/California Institute of Technology

New CoRoT Exoplanets

As of 14 June 2010, the CoRoT family of exoplanets comprises 15 members - the most recent additions being the following six:

CoRoT-8b: At about 70% of the size and mass of Saturn, CoRoT-8b is moderately small compared to the previously known transiting exoplanets. Its internal structure should be similar to that of ice giants, like Uranus and Neptune in our Solar System. It is the smallest planet discovered by the CoRoT team so far after CoRoT-7b, the first transiting Super-Earth.

CoRoT-10b: The orbit of this planet is so elongated that the planet passes both very close to, and very far away from, its parent star. The amount of radiation it receives from the star varies tenfold in intensity, and scientists estimate that its surface temperature may increase from 250 to 600°C, all in the space of 13 Earth-days (the length of the year on CoRoT-10b).

CoRoT-11b: CoRoT-11, the host star of this planet, rotates around its axis in less than two days. For comparison, the Sun's rotation period is 26 days. It is particularly difficult to confirm planets around rapidly rotating stars, so this detection marks a significant achievement for the CoRoT team.

CoRoT-12b, 13b and 14b: These three planets all orbit close to their host star but have very different properties. Although CoRoT-13b is smaller than Jupiter, it is twice as dense. This suggests the presence of a massive rocky core inside the planet. With a radius that is 16 times larger than the Earth, CoRoT-12b belongs to the family of 'bloated hot Jupiters', whose anomalously large sizes are due to the intense stellar radiation they receive. Amazingly, CoRoT-14b which is even closer to its parent star has a size similar to that of Jupiter. Its mass is 7.5 times the mass of Jupiter making the planet 6 times denser. Such a combination, very massive and very hot, is rare and CoRoT-14b is the second such planet discovered so far.

CoRoT-15b: The brown dwarf. CoRoT-15b's mass is about 60 times that of Jupiter. This makes it incredibly dense, about 40 times more so than Jupiter. For that reason, it is classified as a brown dwarf, intermediate in nature between planets and stars. Brown dwarfs are much rarer than planets, which makes this discovery all the more exciting.

The figure above depicts the relative sizes and distances from parent stars of the CoRoT exoplanets.

Illustration credit: CNES

Neptune, by Voyager 2

Credit: NASA


While Neptune may be the farthest of the eight planets orbiting the Sun (as defined by the International Astronomical Union (IAU)), it certainly doesn't lack for interesting features. While Uranus' atmosphere is primarily a mix of hydrogen, helium and methane (the last giving the planet its light blue hue), Neptune's atmosphere is primarily made up of methane, which is what gives the planet its deep blue color. Neptune is the smallest of the four gas giants, but it's also the densest of that set.

Although Neptune receives only 3% as much sunlight as Jupiter, it showed several large dark spots reminiscent of Jupiter's hurricane-like storms. The largest spot is named the "Great Dark Spot" and is an anticyclone similar to Jupiter's Great Red Spot. Neptune's Great Dark Spot is comparable in size, relative to the planet, and at the same latitude (22° South latitude) as Jupiter's Great Red Spot. However, Neptune's Great Dark Spot is far more variable in size and shape than the Great Red Spot. Another spot, named "D2" by the Voyager 2 scientists, is located far to the south of the Great Dark Spot, at 55° South latitude. It is almond-shaped, with a bright central core, and moves eastward around the planet in about 16 hours.

Most of the winds on Neptune blow in a westward direction, which is retrograde, or opposite to the rotation of the planet. Near the Great Dark Spot, there are retrograde winds blowing up to 1,500 miles an hour (2,400 kph) -- the strongest winds measured on any planet, including windy Saturn.

The only spacecraft to date to fly past Neptune was Voyager 2, which hurtled past Neptune's north pole on August 25, 1989. Voyager 2's closest approach was a mere 4,950 km from the planet, the closest approach Voyager 2 made of any planet. The fly-by of Neptune put Voyager 2 on a course 48° south of the ecliptic plane of the solar system, roughly toward the constellation Canis Major and the star Sirius, with a rate of speed about 470 million km per year.