New Studies Propose Two New Planets Beyond Pluto

New calculations from an international team of researchers suggest that there could be two unknown planets beyond Pluto.

In two new studies, published in the Monthly Notices of the Royal Astronomical Society, scientists from the University of Madrid and the University of Cambridge posit that two, or more, unknown planets are responsible for unusual behaviour beyond Neptune.

Objects, in that far-flung part of the Solar System, don’t act like we believe they should: the paths they move along do not have the orbital inclinations and axes that astronomers would expect to see, based on current theory of what researchers call "trans-Neptunian objects."

Unless, the astrophysicists posit, there’s something else out there, and, after considering the effects of the “Kozai mechanism,” the effect an object orbiting further out from a gravitational source can have one orbiting futher in, they now believe there are at least two mysterious planets at play.

“Our results may be truly revolutionary for astronomy,” says co-author Carlos de la Fuente Marcos in a news release, but the team says this is still a hypothesis.

To prove it, scientists will have to overcome two hurdles. Not only does the new theory challenge astrophysicists' current thinking about how the solar system came to be, but the sample size used in the study’s calculations contains only 13 objects.

However, the team promises that with a larger sample size, coming soon, and new research (a recently-discovered planet-in-process is much further away from a star than scientists suspected to be possible), they’ll soon have even more evidence that our solar system may be even bigger than thought.

More Information
'Flipping minor bodies: what comet 96P/Machholz 1 can tell us about the orbital evolution of extreme trans-Neptunian objects and the production of near-Earth objects on retrograde orbits' published in the Monthly Notices of the Royal Astronomical Society - 10.1093/mnras/stu2230

The origin of Uranus and Neptune elucidated?

Uranus and Neptune as seen from NASA's Voyager mission. Credit: NASA

A team of French-American researchers led by the UTINAM Institute (CNRS/Université de Franche-Comté) has just proposed a solution to the problematic chemical composition of Uranus and Neptune, thus providing clues for understanding their formation.

The researchers focused on the positioning of these two outermost planets of the Solar System, and propose a new model explaining how and where they formed.

Their results have been published in The Astrophysical Journal on September 20.

Uranus and Neptune, the outermost planets in the Solar System, each have a mass approximately fifteen times that of the Earth, consisting of up to 90% ice, and highly enriched in carbon.

Because of these particular characteristics, the origin of the two planets remains unresolved today.

Earlier models for their formation, as well as observations of the outer Solar System, could not explain how they formed in the area where they are found today.

This area, which is located very far from the Sun, did not contain sufficient building blocks to form Uranus and Neptune quickly enough before the dissipation of the protosolar nebula.

Once the nebula dissipated, it became impossible for the two planets to accrete gaseous envelopes.

The ESA Herschel Space Observatory recently focused on the isotopic composition of Uranus and Neptune, and especially on the deuterium-to-hydrogen ratio (D/H), a tracer used in planetology to examine the origin of the elements that formed the Solar System.

This isotopic ratio is very sensitive to the temperature of the protosolar nebula, being low close to the Sun, and increasing with the distance.

Dynamic models suggest that Uranus and Neptune formed in the same distant region as the comets, and should therefore have a high D/H ratio.

Surprisingly though, the Herschel measurements show that the D/H ratio in the two planets is much lower than that measured in comets.

This study solves all of these problems at once, by proposing a new model based on detailed simulations of the distribution and transport of the most abundant volatile elements in the Solar System's protosolar nebula (H2O, CO and N2).

These simulations show the presence of density "peaks" of solids in regions where nebular temperature is low enough for gas condensation (or ice lines).

The results show that Uranus and Neptune apparently formed on the Carbon Monoxide (CO) ice line, which would explain why they consist of carbon-rich solids but nitrogen-depleted gas.

Accretion of large quantities of CO with low quantities of cometary H2O gives the D/H value measured in the atmosphere of these planets.

Moreover, since the nitrogen ice line is located slightly farther away, the planets formed naturally poor in nitrogen..

The proposed model gives carbon and nitrogen abundances that are consistent with observed values, and establishes that the formation of Uranus and Neptune took place in this distant region.

More information: "The Measured Compositions of Uranus and Neptune from their Formation on the CO Ice Line," Mohamad Ali-Dib, Olivier Mousis, Jean-Marc Petit and Jonathan I. Lunine, Astrophysical Journal, Vol. 793, Issue 1, September 2014. Arxiv.org/abs/1407.2568

New Horizons crossed the orbit of Neptune

Artist's concept of NASA's New Horizons probe flying past the dwarf planet Pluto on July 14, 2015. 

New Horizons crossed the orbit of Neptune on Aug. 25, 2014, 25 years to the day after NASA's Voyager 2 spacecraft flew by the distant blue planet.

Credit: Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

A speedy NASA probe has crossed the orbit of Neptune, notching one more spaceflight milestone on its way toward a historic flyby of Pluto next summer.

New Horizons, which is scheduled to zoom through the Pluto system on July 14, 2015, passed Neptune's orbit today (Aug. 25), 25 years to the day after NASA's Voyager 2 probe executed the first-ever flyby of faraway Neptune and its icy moon Triton.

New Horizons team members took the opportunity provided by this spaceflight coincidence to pay tribute to Voyager 2, the only probe ever to visit the "ice giant" planets Uranus and Neptune.

Scanning the skies for Exoplanets and Exomoons in other solar systems

The best prospect for habitable exomoons may be around gas giants. 

Credit: NASA

The first exoplanet was discovered in 1994.

Twenty years later, NASA's exoplanet catalog lists more than 1700 planets confirmed around other stars.

Most of these extra-solar-systems have been measured by changes in light spectra, in stellar motion or dust disks around stars.

Some exoplanets-more than 40 as of today-have even been directly photographed.

Jupiter's moons

One way or the other, we know that exoplanets are out there in abundance, in places we thought they would be and in places we didn't dream a planet could possibly exist. So what comes next? Finding moons.

Exomoons are naturally formed satellites circling around planets in other solar systems. Like the exoplanets themselves, we assume that exomoons are out there in relatively high abundance.

This assumption is based partly upon what we see around us in our own Solar System and partly upon our hypotheses about planetary formation.

Saturn's moons

This is what we observe in our own Solar System: moons are extremely common.

From Earth's one Moon to Jupiter's (currently known) fifty, every planet in the Solar System one astronomical unit or more from the Sun has a natural satellite.

Even Pluto, no longer officially classified as a planet, has a smaller companion circling around it.

Of note, the solid bodies such as Earth and Pluto have very few companions, while gaseous bodies Jupiter, Saturn, Uranus and Neptune have many.

Pluto and Charon

Furthermore, the masses of the Moon and Charon have a very specific relationship to Earth and Pluto in terms of mass: each satellite is about 10-2 the mass of their parent planet.

By contrast, the ratio of satellite masses to parent planet masses for the gas giants is very different: 10-4.

The differences in mass-ratio, how massive the moon is compared to the parent planet, and the differences in composition between the moons of solid planets and those of the gas giants led to a search for different formation scenarios for Earth's moon and the moons of the outer planets.

This is the current hypothesis: that there are two different methods of satellite formation at work in our Solar System.

Amy Barr Mlinar

Both methods were recently reviewed by Dr.Amy Barr Mlinar of Brown University at the Space Telescope Science institute Spring Symposium.

"This has been worked out starting about in the 1960's up through now," said Barr, "You have this [moon/planet] mass ratio of about 10-2 for solid planets, and a [moon/planet] mass ratio of about 10-4 for planets with a gaseous envelope."

Essentially, difference in mass ratios reflects the two completely different origins of our Moon and the satellites of Jupiter.

At the high end of the moon/planet mass ratio, 10-2 are the satellites of solid bodies (Earth and Pluto). These moons were formed from collisions.

Sometime in the distant past an object some large percentage of Earth's size struck the Earth, knocking material away that later coalesced into the Moon. The same is likely true of Charon, Pluto's companion.

Read the full article here

NASA Cassini Image: Looking beyond Saturn to view Uranus

This view from NASA's Cassini spacecraft features a blue planet, but unlike the view from July 19, 2013 (PIA17172 The Day the Earth Smiled) that featured our home planet, this blue orb is Uranus, imaged by Cassini for the first time.

Credit: NASA /JPL-Caltech /Space Science Institute

Uranus is a pale blue in this natural colour image because its visible atmosphere contains methane gas and few aerosols or clouds.

Methane on Uranus and its sapphire-coloured sibling, Neptune, absorbs red wavelengths of incoming sunlight, but allows blue wavelengths to escape back into space, resulting in the predominantly bluish color seen here.

Cassini imaging scientists combined red, green and blue spectral filter images to create a final image that represents what human eyes might see from the vantage point of the spacecraft.

Uranus

Uranus has been brightened by a factor of 4.5 to make it more easily visible. The outer portion of Saturn's A ring, seen at bottom right, has been brightened by a factor of two.

The bright ring cutting across the image center is Saturn's narrow F ring.

Uranus was approximately 28.6 astronomical units from Cassini and Saturn when this view was obtained.

An astronomical unit is the average distance from Earth to the sun, equal to 93,000,000 miles (150,000,000 kilometers).

Neptune

The view was acquired by the Cassini narrow-angle camera at a distance of approximately 614,300 miles (988,600 kilometers) from Saturn on April 11, 2014.

Image scale at Uranus is approximately 16,000 miles (25,700 kilometers) per pixel.

Image scale at Saturn's rings is approximately 4 miles (6 kilometers) per pixel.

In the image, the disk of Uranus is just barely resolved.

The solar phase angle at Uranus, seen from Cassini, is 11.9 degrees.

NASA WISE: Uranus and the Planet X myth - debunked

The hunt for Planet X began after Uranus (pictured) was first discovered in 1781 with astrologers hoping it could explain the wobbly orbit of Uranus around the sun

It was an elusive planet that for 200 years appeared to explain Uranus's wobbly orbit and there was the sister sun theorised to be near our solar system that caused asteroids to swerve toward Earth.

There is just one problem: neither "Planet X" nor "Nemesis" ever existed, researchers now say. Although, there is still a trace of doubt.

"The outer solar system probably does not contain a large gas giant planet ("Planet X"), or a small, companion star ("Nemesis")," concluded University of Pennsylvania astronomer Kevin Luhman, who directed the study using NASA's Wide-field Infrared Survey Explorer (WISE) telescope.

The results were published in the most recent edition of The Astrophysical Journal.

Most theories had estimated Planet X to be up to four times the size of Jupiter—the biggest planet in our solar system.

They suggested it would be found some 1,486 billion kilometers (923 billion miles) from the sun, or about 10,000 times farther than the Earth's orbit.

But the images gathered by the telescope did not detect any object larger than Jupiter.

Luhman doesn't rule out the possibility that a planet is lurking somewhere in the asteroid belt.

It would be hard to find if it were closely aligned with a bright star that blinds the telescope or were much smaller than had been theorized.

A computer generated NASA montage obtained 29 August 2002 from images collected by the Voyager 2 spacecraft shows Neptune (Lower-L) as it would appear from a spacecraft approaching Triton, Neptune's largest moon

But after this latest survey, Luhman said the odds of finding one are very unlikely: "That is like a one in a hundred chance."

History of Planet X
Scientists first imagined the existence of Planet X in 1781, when they discovered Uranus, a gas giant that astonished astronomers with its orbital variations, apparently incompatible with Newton's laws of gravity.

Observers concluded that these irregularities could be explained by the existence of another, unknown planet that was exerting its own gravitational force.

Attempts to track this mysterious Planet X led to the discovery of Neptune in 1846. But the estimated mass of Neptune couldn't explain the deviations of Uranus's orbit.

That led astronomers to continue their search for Planet X—which, in turn, led to the discovery of Pluto in 1930. But the dwarf planet was also too small to explain Uranus's irregular path around the sun.

Finally, in the 1990s, researchers determined that they had slightly overestimated the mass of Neptune, which meant the planet could in fact be the reason for Uranus's orbital behaviour.

Yet Planet X believers were still not convinced.

Sister sun killed dinosaurs?
The existence of Nemesis, a sun-like star nearby, was first posited in the 1980s. The star, by occasionally coming closer to the sun, interfered with the orbit of comets and asteroids leading them to occasionally hit the Earth.

Collisions like these are blamed for the five mass extinctions over the last 540 million years—the most recent being the dinosaur extinction 65 million years ago.

"So over the years, there have been different pieces of evidence suggesting there might be something there," Luhman explained to reporters but the WISE telescope didn't find anything.

The hunt for Planet X and Nemesis may have turned up empty, but the study did uncover 3,525 stars and brown dwarfs, celestial objects whose mass puts them between a star and a large planet, within 500 light years of the sun.

"Neighbouring star systems that have been hiding in plain sight just jump out in the WISE data," said Ned Wright, a University of California, Los Angeles astronomer who contributed to the study.

Hubble images reveal Neptune's 'lost' inner moon

Naiad is the encircled point of light just to the left of Neptune.

Neptune's tiny, innermost moon, Naiad, has now been seen for the first time since it was discovered by Voyager's cameras in 1989.

Dr. Mark Showalter, a senior research scientist at the SETI Institute in Mountain View, California, announced the result today in Denver, Colorado, at the annual meeting of the Division for Planetary Sciences of the American Astronomical Society.

He and collaborators Dr. Jack Lissauer of the NASA Ames Research Center, Dr. Imke de Pater of UC Berkeley, and Robert French of the SETI Institute, also released a dramatic new image of Neptune's puzzling rings and ring-arcs, which were first imaged by Voyager.

Mark Showalter

"Naiad has been an elusive target ever since Voyager left the Neptune system," said Dr. Showalter. From Earth, Neptune is 2 million times brighter than Naiad, andthetwo are separated by only one arcsecond.

"This is equivalent to the width of a human hair from 50 feet away," noted collaborator Lissauer. The team of astronomers needed to develop new techniques to suppress Neptune's glare.

Naiad was finally revealed, moving across a sequence of eight images taken during December 2004.

Strangely, Naiad appears to have veered significantly off course. The astronomers are puzzled by the fact that Naiad is now far ahead of its predicted orbital position.

They wonder whether gravitational interactions with one of Neptune's other moons may have caused it to speed up, although the details remain mysterious.

Further observations will be needed in order to understand Naiad's motion.

In addition to its moons, Neptune hosts a family faint rings and ring-arcs. The arcs have been changing slowly in the years since their discovery.

Whereas Voyager saw a set of four closely-spaced arcs, the leading two arcs have been fading away, and are completely absent from the newest images.

The trailing arcs, however, are essentially unchanged. This system of arcs is probably confined by the gravitational effects of the nearby moon Galatea, but the reason for the long-term changes is unknown.

Dr. de Pater has also been following the ongoing evolution of the arcs from the 10-meter W. M. Keck telescope in Hawaii.

The Mighty Winds of Uranus and Neptune

This image of Uranus was obtained in 2005 by the Hubble Space Telescope. Rings, southern collar and a bright cloud in the northern hemisphere are visible.

CREDIT: NASA, ESA, and M. Showalt

The powerful winds of Uranus and Neptune are apparently confined to tight layers in both planets, researchers have determined.

These findings could shed light on how those immensely strong winds are born, and how giant planets form and evolve over time, scientists added.

Giant planets in the outer solar system, like Uranus and Neptune, are dominated by winds that can reach supersonic speeds and jet streams 10 to 15 times stronger than those found on Earth, judging by images of how clouds race by on those worlds.

Yohai Kaspi

However, just how deep those winds reached was unknown until now, hidden as those lower depths are beneath those dense layers of clouds.

"This has been an open question for the last 25 years," study lead author Yohai Kaspi, a planetary scientist at the Weizmann Institute of Science in Rehovot, Israel, told reporters.

This image shows schematic of the jet streams on the planet Neptune. Scientist have found that the atmosphere's circulation is characterized by westward flow near the equator with velocities reaching 750 mph (1200 km/hr), and an eastward flow at higher latitudes in both the northern and southern hemispheres with velocities reaching 560 mph (900 km/hr). 

The wind velocities decay towards the planet's dense fluid interior. Image released May 15, 2013. 

CREDIT: Yohai Kaspi, Weizmann Institute of Science/NASA

Kaspi and his colleagues focused on Uranus and Neptune, which are both "ice giants" — massive planets with icy atmospheres.

The winds of Uranus can blow clouds up to 560 miles per hour (900 kilometers per hour), while Neptune's winds can reach up to 1,500 miles per hour (2,400 kilometers per hour), the fastest planetary winds detected yet in the solar system.

The researchers investigated the gravity fields of those worlds using data gathered by NASA's Voyager 2 spacecraft and ground-based telescopes.

The strength of a planet's gravity field depends on its amount of mass, and this strength can vary over the surface of a planet depending on the amount of mass lying under it.

By analyzing the gravity fields of these worlds, the investigators could deduce how their atmospheres circulated.

The scientists discovered the winds blow in relatively thin weather layers no more than 600 miles (1,000 kilometers) deep on both planets. For comparison, Neptune is about 30,600 miles (49,250 km) in diameter, while Uranus is approximately 31,500 miles (50,700 km) wide.

These findings help reveal how these winds originate, researchers said.

Past studies have suggested the winds on Uranus and Neptune might arise one of two ways — either shallow processes in their outer atmospheres, or deeper atmospheric mechanisms extending into their interiors.

The researchers found the windy layers of Uranus and Neptune occupy the outermost 0.15 and 0.2 percent of their masses, respectively, suggesting that shallow processes drive those winds, such as swirling caused by moisture condensing and evaporating in the atmosphere.

This image of Neptune was captured by NASA's Voyager 2 spacecraft during an August 1989. Neptune's Great Dark Spot dominates the center along with bright, white. To the south is the bright feature nicknamed "Scooter." 

Still farther south is the "Dark Spot 2," which has a bright core. Each feature moves eastward at a different velocity, so it is only occasionally that they appear close to each other as shown here 

CREDIT: NASA

The new study has implications for how scientists understand how planets form.

"When it comes to thinking about the effects of dynamics on planetary formation, we're saying the bottom 90 percent of giant planets is static," Kaspi said.

In the future, the Cassini spacecraft currently orbiting Saturn and NASA's Juno probe that is scheduled to reach Jupiter can analyze the gravity fields of those giant planets and help better explain their winds as well.

Do Auroras Exist Outside our Solar System?

University of Leicester planetary scientists have found new evidence suggesting auroras -- similar to Earth's Aurora Borealis -- occur on bodies outside our solar system. 

Auroras occur on several planets within our solar system, and the brightest -- on Jupiter -- are 100 times brighter than those on Earth. 

However, no auroras have yet been observed beyond Neptune.

A new study led by University of Leicester lecturer Dr. Jonathan Nichols has shown that processes strikingly similar to those which power Jupiter's auroras could be responsible for radio emissions detected from a number of objects outside our solar system.

In addition, the radio emissions are powerful enough to be detectable across interstellar distances -- meaning that auroras could provide an effective way of observing new objects outside our solar system.

Auroras occur when charged particles in an object's magnetosphere collide with atoms in its upper atmosphere, causing them to glow.

However, before hitting the atmosphere, these particles also emit radio waves into space.

The study, "Origin of Electron Cyclotron Maser Induced Radio Emissions at Ultracool Dwarfs: Magnetosphere-Ionosphere Coupling Currents," which recently appeared in the Astrophysical Journal, shows that this phenomenon is not limited to our solar system.

It shows that the radio emissions from a number of ultracool dwarfs may be caused in a very similar, but significantly more powerful, way to Jupiter's auroras.

Dr. Nichols, a Lecturer and Research Fellow in the University of Leicester's Department of Physics and Astronomy, said: "We have recently shown that beefed-up versions of the auroral processes on Jupiter are able to account for the radio emissions observed from certain "ultracool dwarfs" -- bodies which comprise the very lowest mass stars -- and "brown dwarfs" -- 'failed stars' which lie in-between planets and stars in terms of mass.

"These results strongly suggest that auroras do occur on bodies outside our solar system, and the auroral radio emissions are powerful enough -- one hundred thousand times brighter than Jupiter's -- to be detectable across interstellar distances."

The paper, which also involved researchers at the Center for Space Physics, Boston University, USA, could have major implications for the detection of planets and objects outside our solar system which could not be discovered with other methods.

Uranus: Keck observations brings weather into sharp focus

A paired picture of Uranus, the sharpest, most detailed picture of the distant planet to date, reveals a raft of new details about the planet's enigmatic atmosphere. 

The north pole of Uranus (to the right in the picture) is characterised by a swarm of storm-like convective features, and an unusual scalloped pattern of clouds encircles the planet's equator. 

The infrared image was taken using the Keck II telescope in Hawaii. 

Credit: Lawrence Sromovsky, Pat Fry, Heidi Hammel, Imke de Pater

In 1986, when Voyager swept past Uranus, the probe's portraits of the planet were "notoriously bland," disappointing scientists, yielding few new details of the planet and its atmosphere, and giving it a reputation as the most boring planet of the solar system.

Now, however, thanks to a new technique applied at the Keck Observatory, Uranus is coming into sharp focus through high-resolution infrared images, revealing in incredible detail the bizarre weather of the seventh planet from the sun.

The images were released in Reno, Nev. today (Oct. 17, 2012) at a meeting of the American Astronomical Society's Division of Planetary Sciences and provide the best look to date of Uranus's complex and enigmatic weather.

The planet's deep blue-green atmosphere is thick with hydrogen, helium and methane, Uranus's primary condensable gas.

Larry Sromovsky

Winds blow mainly east to west at speeds up to 560 miles per hour, in spite of the small amounts of energy available to drive them.

Its atmosphere is almost equal to Neptune's as the coldest in our solar system with cloud-top temperatures in the minus 360-degree Fahrenheit range, cold enough to freeze methane.

Large weather systems, which are probably much less violent than the storms we know on Earth, behave in bizarre ways on Uranus, explains Larry Sromovsky, a University of Wisconsin-Madison planetary scientist who led the new study using the Keck II telescope.

"Some of these weather systems," Sromovsky notes, "stay at fixed latitudes and undergo large variations in activity. Others are seen to drift toward the planet's equator while undergoing great changes in size and shape. Better measures of the wind fields that surround these massive weather systems are the key to unraveling their mysteries."

Imke de Pater

To get a better picture of atmospheric flow on Uranus, Sromovsky and colleagues Pat Fry, also of UW-Madison, Heidi Hammel of the Association of Universities for Research in Astronomy (AURA), and Imke de Pater of the University of California at Berkeley, used new infrared techniques to detect smaller, more widely distributed weather features whose movements can help scientists trace the planet's pattern of blustery winds.

"We're seeing some new things that before were buried in the noise," says Sromovsky, a senior staff scientist at UW-Madison's Space Science and Engineering Center.

Heidi Hammel

"My first reaction to these images was 'wow' and then my second reaction was WOW," says AURA's Heidi Hammel, a co-investigator on the new observations and an expert on the atmospheres of the solar system's outer planets.

"These images reveal an astonishing amount of complexity in Uranus's atmosphere. We knew the planet was active, but until now much of the activity was masked by noise in our data."

The complexity of Uranus's weather is puzzling, Sromovsky explains. The primary driving mechanism must be solar energy because there is no detectable internal energy source.

"But the sun is 900 times weaker there than on Earth because it is 30 times further from the sun, so you don't have the same intensity of solar energy driving the system," explains Sromovsky.

"Thus the atmosphere of Uranus must operate as a very efficient machine with very little dissipation. Yet the weather variations we see seem to defy that requirement."

The new Keck II pictures of the planet, according to Sromovsky, are the "most richly detailed views of Uranus yet obtained by any instrument on any observatory.

No other telescope could come close to producing this result." Sromovsky and his colleagues used Keck II, located on the summit of Hawaii's 14,000-foot extinct volcano Mauna Kea, to capture a series of images that, when combined, help increase the signal to noise ratio and thus tease out weather features that are otherwise obscured.

In two nights of observing under superb conditions, Sromovsky's group was able to obtain exposures of the planet that provide a clear view of the planet's cloudy features, including several new to science.

The group used two different filters in an effort to characterize cloud features at different altitudes. "The main objective was to find a larger number of cloud features by detecting those that were previously too subtle to be seen, so we could better define atmospheric motions," Sromovsky notes.

New features found by the Wisconsin group include a scalloped band of clouds just south of Uranus's equator and a swarm of small convective features in the north polar regions of the planet, features that have never been seen in the southern polar regions.

"This is a very asymmetric situation," says the Wisconsin scientist. "There is certainly something different going on in those two polar regions." One possible explanation, is that methane is pushed north by an atmospheric conveyor belt toward the pole where it wells up to form the convective features observed by Sromovsky's group.

"The 'popcorn' appearance of Uranus's pole reminds me very much of a Cassini image of Saturn," adds de Pater.

Read more here

Voyager 1 & 2: The Interstellar Mission

The twin Voyager 1 and 2 spacecraft continue exploring where nothing from Earth has flown before.

In the 34th year after their 1977 launches, they each are much farther away from Earth and the Sun than Pluto.

Voyager 1 and 2 are now in the "Heliosheath" - the outermost layer of the heliosphere where the solar wind is slowed by the pressure of interstellar gas.

Both spacecraft are still sending scientific information about their surroundings through the Deep Space Network (DSN).


The primary mission was the exploration of Jupiter and Saturn.

After making a string of discoveries there, such as recording active volcanoes on Jupiter's moon Io and intricacies of Saturn's rings, the mission was extended.

Voyager 2 went on to explore Uranus and Neptune, and is still the only spacecraft to have visited those outer planets.

The adventurers' current mission, the Voyager Interstellar Mission (VIM), will explore the outermost edge of the Sun's domain and beyond.

Mission Objective

The mission objective of the Voyager Interstellar Mission (VIM) is to extend the NASA exploration of the solar system beyond the neighbourhood of the outer planets to the outer limits of the Sun's sphere of influence, and possibly beyond.

This extended mission is continuing to characterize the outer solar system environment and search for the heliopause boundary, the outer limits of the Sun's magnetic field and outward flow of the solar wind.

Penetration of the heliopause boundary between the solar wind and the interstellar medium will allow measurements to be made of the interstellar fields, particles and waves unaffected by the solar wind.

The Planets: The Retro Space Poster Art of Steve Thomas

Visit Steve Thomas's site for more great poster art. A great new creative experience in retro-style Art, with more than a touch of Humour.

Neptune Completes First Orbit Since Discovery In 1846

This illustration is a composite of numerous separate Hubble WFC3 images. 

A colour image composed of exposures made through three color filters shows the disk of Neptune, revealing clouds in its atmosphere. 

48 separate images from a single filter were brightened to reveal the very faint moons. The white dots are Neptune's inner moons moving along their orbits during Hubble's observations. 

The solid green lines trace the full orbit of each moon. Note in this image Triton position and size is not shown to scale. 

The spacing of the moon images follows the timing of each Hubble exposure. About 30 moons are known to orbit Neptune, most of which are too faint or orbit too far away to appear in these images.

Illustration credit: NASA, ESA, and Z. Levay (STScI).

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.

'This Planet Tastes Funny,' According To Spitzer

'This Planet Tastes Funny,' According To Spitzer

NASA's Spitzer Space Telescope has discovered something odd about a distant planet - it lacks methane, an ingredient common to many of the planets in our solar system.

"It's a big puzzle," said Kevin Stevenson, a planetary sciences graduate student at the University of Central Florida in Orlando, lead author of a study appearing tomorrow, April 22 in the journal Nature.

"Models tell us that the carbon in this planet should be in the form of methane. Theorists are going to be quite busy trying to figure this one out."

The discovery brings astronomers one step closer to probing the atmospheres of distant planets the size of Earth. The methane-free planet, called GJ 436b, is about the size of Neptune, making it the smallest distant planet that any telescope has successfully "tasted," or analyzed.

Eventually, a larger space telescope could use the same kind of technique to search smaller, Earth-like worlds for methane and other chemical signs of life, such as water, oxygen and carbon dioxide.

Transit Image of Neptune's Moon Despina: Missing Voyager 2 Image

(Image: NASA/JPL/Ted Stryk)

Never-before-seen images of Neptune's moon Despina passing in front of the ice giant planet were found in the dusty archives of the Voyager 2 mission, which launched in 1977 and is now heading out of the solar system.

Ted Stryk, an amateur astronomer with a passion for old data, found the 20-year-old frames, which were originally taken for atmospheric data. That may be why the transit images had been missed before – atmospheric scientists might have deliberately ignored the object's shadow on Neptune's cloud tops. These "new" images could help scientists pin down the orbit of the 148-km-wide moon.

You can now see Neptune in the Night Sky

Then felt I like some watcher of the skies
When a new planet swims into his ken

Thus wrote John Keats, referring to William Herschel's discovery of the planet Uranus a few years before in 1781. Measurements of the position of Uranus soon showed that it was under the gravitational influence of another planet, farther out in the solar system.