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Solar System: Things to Know This Week

Our solar system is a jewel box filled with a glittering variety of beautiful worlds–and not all of them are planets. This week, we present our solar system’s most marvelous moons.

1. Weird Weather: Titan

Saturn’s hazy moon Titan is larger than Mercury, but its size is not the only way it’s like a planet. Titan has a thick atmosphere, complete with its own “water cycle” – except that it’s way too cold on Titan for liquid water. Instead, rains of liquid hydrocarbons like ethane and methane fall onto icy mountains, run into rivers, and gather into great seas. Our Cassini spacecraft mapped the methane seas with radar, and its cameras even caught a glimpse of sunlight reflecting off the seas’ surface. Learn more about Titan: saturn.jpl.nasa.gov/science/titan/

2. Icy Giant: Ganymede

Jupiter’s moon Ganymede is the largest in the solar system. It’s bigger than Mercury and Pluto, and three-quarters the size of Mars. It’s also the only moon known to have its own magnetic field. Details: solarsystem.nasa.gov/planets/ganymede/indepth

3. Retrograde Rebel: Triton

Triton is Neptune’s largest moon, and the only one in the solar system to orbit in the opposite direction of its planet’s rotation, a retrograde orbit. It may have been captured from the Kuiper Belt, where Pluto orbits. Despite the frigid temperatures there, Triton has cryovolcanic activity – frozen nitrogen sometimes sublimates directly to gas and erupts from geysers on the surface. More on Triton: solarsystem.nasa.gov/planets/triton/indepth

4. Cold Faithful: Enceladus

The most famous geysers in our solar system (outside of those on Earth) belong to Saturn’s moon Enceladus. It’s a small, icy body, but Cassini revealed this world to be one of the solar system’s most scientifically interesting destinations. Geyser-like jets spew water vapor and ice particles from an underground ocean beneath the icy crust of Enceladus. With its global ocean, unique chemistry and internal heat, Enceladus has become a promising lead in our search for worlds where life could exist. Get the details: saturn.jpl.nasa.gov/science/enceladus/

5. Volcano World: Io

Jupiter’s moon Io is subjected to tremendous gravitational forces that cause its surface to bulge up and down by as much as 330 feet (100 m). The result? Io is the most volcanically active body in the Solar System, with hundreds of volcanoes, some erupting lava fountains dozens of miles high. More on Io’s volcanoes: solarsystem.nasa.gov/planets/io/indepth

6. Yin and Yang Moon: Iapetus

When Giovanni Cassini discovered Iapetus in 1671, he observed that one side of this moon of Saturn was bright and the other dark. He noted that he could only see Iapetus on the west side of Saturn, and correctly concluded that Iapetus had one side much darker than the other side. Why? Three centuries later, the Cassini spacecraft solved the puzzle. Dark, reddish dust in Iapetus’s orbital path is swept up and lands on the leading face of the moon. The dark areas absorb energy and become warmer, while uncontaminated areas remain cooler. Learn more: saturn.jpl.nasa.gov/news/2892/cassini-10-years-at-saturn-top-10-discoveries/#nine

7. A Double World: Charon and Pluto

At half the size of Pluto, Charon is the largest of Pluto’s moons and the largest known satellite relative to its parent body. The moon is so big compared to Pluto that Pluto and Charon are sometimes referred to as a double planet system. Charon’s orbit around Pluto takes 6.4 Earth days, and one Pluto rotation (a Pluto day) takes 6.4 Earth days. So from Pluto’s point of view Charon neither rises nor sets, but hovers over the same spot on Pluto’s surface, and the same side of Charon always faces Pluto. Get the details: www.nasa.gov/feature/pluto-and-charon-new-horizons-dynamic-duo

8. “Death Star” Moon: Mimas

Saturn’s moon Mimas has one feature that draws more attention than any other: the crater Herschel, which formed in an impact that nearly shattered the little world. Herschel gives Mimas a distinctive look that prompts an oft-repeated joke. But, yes, it’s a moon. More: olarsystem.nasa.gov/planets/mimas

9. Don’t Be Afraid, It’s Just Phobos

In mythology, Mars is a the god of war, so it’s fitting that its two small moons are called Phobos, “fear,” and Deimos, “terror.” Our Mars Reconnaissance Orbiter caught this look at Phobos, which is roughly 17 miles (27 km) wide. In recent years, NASA scientists have come to think that Phobos will be torn apart by its host planet’s gravity. Details: www.nasa.gov/feature/goddard/phobos-is-falling-apart

Learn more about Phobos: solarsystem.nasa.gov/planets/phobos/indepth

10. The Moon We Know Best

Although decades have passed since astronauts last set foot on its surface, Earth’s moon is far from abandoned. Several robotic missions have continued the exploration. For example, this stunning view of the moon’s famous Tycho crater was captured by our Lunar Reconnaissance Orbiter, which continues to map the surface in fine detail today. More: www.lroc.asu.edu/posts/902

Discover more lists of 10 things to know about our solar system HERE.

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The four Galilean moons, Ganymede, Callisto, Europa, and Io.

These four are the largest moons in orbit around Jupiter. In fact, they are large enough to be viewed using a simple pair of binoculars!

These four giants, especially Europa, have been of interest to scientists due to their strange formations and liquid water that has the potential to sustain life.

Images belong to NASA.

Magnetospheres: How Do They Work?

The sun, Earth, and many other planets are surrounded by giant magnetic bubbles.

Space may seem empty, but it’s actually a dynamic place, dominated by invisible forces, including those created by magnetic fields.  Magnetospheres – the areas around planets and stars dominated by their magnetic fields – are found throughout our solar system. They deflect high-energy, charged particles called cosmic rays that are mostly spewed out by the sun, but can also come from interstellar space. Along with atmospheres, they help protect the planets’ surfaces from this harmful radiation.

It’s possible that Earth’s protective magnetosphere was essential for the development of conditions friendly to life, so finding magnetospheres around other planets is a big step toward determining if they could support life.

But not all magnetospheres are created equal – even in our own backyard, not all planets in our solar system have a magnetic field, and the ones we have observed are all surprisingly different.

Earth’s magnetosphere is created by the constantly moving molten metal inside Earth. This invisible “force field” around our planet has an ice cream cone-like shape, with a rounded front and a long, trailing tail that faces away from the sun. The magnetosphere is shaped that way because of the constant pressure from the solar wind and magnetic fields on the sun-facing side.

Earth’s magnetosphere deflects most charged particles away from our planet – but some do become trapped in the magnetic field and create auroras when they rain down into the atmosphere.

We have several missions that study Earth’s magnetosphere – including the Magnetospheric Multiscale mission, Van Allen Probes, and Time History of Events and Macroscale Interactions during Substorms (also known as THEMIS) – along with a host of other satellites that study other aspects of the sun-Earth connection.

Mercury, with a substantial iron-rich core, has a magnetic field that is only about 1% as strong as Earth’s. It is thought that the planet’s magnetosphere is stifled by the intense solar wind, limiting its strength, although even without this effect, it still would not be as strong as Earth’s. The MESSENGER satellite orbited Mercury from 2011 to 2015, helping us understand our tiny terrestrial neighbor.

After the sun, Jupiter has by far the biggest magnetosphere in our solar system – it stretches about 12 million miles from east to west, almost 15 times the width of the sun. (Earth’s, on the other hand, could easily fit inside the sun.) Jupiter does not have a molten metal core like Earth; instead, its magnetic field is created by a core of compressed liquid metallic hydrogen.

One of Jupiter’s moons, Io, has intense volcanic activity that spews particles into Jupiter’s magnetosphere. These particles create intense radiation belts and the large auroras around Jupiter’s poles.

Ganymede, Jupiter’s largest moon, also has its own magnetic field and magnetosphere – making it the only moon with one. Its weak field, nestled in Jupiter’s enormous shell, scarcely ruffles the planet’s magnetic field.

Our Juno mission orbits inside the Jovian magnetosphere sending back observations so we can better understand this region. Previous observations have been received from Pioneers 10 and 11, Voyagers 1 and 2, Ulysses, Galileo and Cassini in their flybys and orbits around Jupiter.

Saturn’s moon Enceladus transforms the shape of its magnetosphere. Active geysers on the moon’s south pole eject oxygen and water molecules into the space around the planet. These particles, much like Io’s volcanic emissions at Jupiter, generate the auroras around the planet’s poles. Our Cassini mission studies Saturn’s magnetic field and auroras, as well as its moon Enceladus.

Uranus’ magnetosphere wasn’t discovered until 1986 when data from Voyager 2’s flyby revealed weak, variable radio emissions. Uranus’ magnetic field and rotation axis are out of alignment by 59 degrees, unlike Earth’s, whose magnetic field and rotation axis differ by only 11 degrees. On top of that, the magnetic field axis does not go through the center of the planet, so the strength of the magnetic field varies dramatically across the surface. This misalignment also means that Uranus’ magnetotail – the part of the magnetosphere that trails away from the sun – is twisted into a long corkscrew.

Neptune’s magnetosphere is also tilted from its rotation axis, but only by 47. Just like on Uranus, Neptune’s magnetic field strength varies across the planet. This also means that auroras can be seen away from the planet’s poles – not just at high latitudes, like on Earth, Jupiter and Saturn.

Does Every Planet Have a Magnetosphere?

Neither Venus nor Mars have global magnetic fields, although the interaction of the solar wind with their atmospheres does produce what scientists call an “induced magnetosphere.” Around these planets, the atmosphere deflects the solar wind particles, causing the solar wind’s magnetic field to wrap around the planet in a shape similar to Earth’s magnetosphere.

What About Beyond Our Solar System?

Outside of our solar system, auroras, which indicate the presence of a magnetosphere, have been spotted on brown dwarfs – objects that are bigger than planets but smaller than stars.

There’s also evidence to suggest that some giant exoplanets have magnetospheres. As scientists now believe that Earth’s protective magnetosphere was essential for the development of conditions friendly to life, finding magnetospheres around exoplanets is a big step in finding habitable worlds.  

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Astronomy and Astrophysics: Facts

Here is a list of some curiosities of astronomy and astrophysics. From our solar system to interstellar space.

Ganymede: Ganymede is the largest and most massive moon of Jupiter and in the Solar System. It has a diameter of 5,268 km and is 8% larger than the planet Mercury. Is the only moon known to have a magnetic field.

Supersonic Wind : Neptune, the eighth and farthest planet from the sun, has the strongest winds in the solar system. At high altitudes speeds can exceed 1,100 mph. That is 1.5 times faster than the speed of sound. 

Io: Jupiter’s moon Io is the most volcanically active world in the Solar System, with hundreds of volcanoes, some erupting lava fountains dozens of miles (or kilometers) high. Io is caught in a tug-of-war between Jupiter’s massive gravity and the smaller but precisely timed pulls from two neighboring moons that orbit further from Jupiter - Europa and Ganymede. 

Magnetosphere of Jupiter: The stronger the magnetic field, the larger the magnetosphere. Some 20,000 times stronger than Earth’s magnetic field, Jupiter’s magnetic field creates a magnetosphere so large it begins to avert the solar wind almost 3 million kilometers before it reaches Jupiter. The magnetosphere extends so far past Jupiter it sweeps the solar wind as far as the orbit of Saturn. 

A scary future - Sun: A red giant star is a dying star in the last stages of stellar evolution. In only a few billion years, our own sun will turn into a red giant star, expand and engulf the inner planets, possibly even Earth. 

Supernova: Supernovas can briefly outshine entire galaxies and radiate more energy than our sun will in its entire lifetime. 

OJ 287: The rotational rate of this massive black hole is one third of the maximum spin rate allowed in General Relativity. This 18 billion-solar-mass black hole powers a quasar called OJ 287 which lies about 3.5 billion light-years away from Earth. 

Olympus Mons: Olympus Mons is a big volcano. It is almost unimaginably huge. It is 550 kilometers (342 miles) across at its base, and the volcanic crater (the technical term is ‘caldera’) at the peak is 80 kilometers (53 miles) long. If you were standing at the edge of the caldera, the volcano is so broad and the slopes are so gradual that the base of the volcano would be beyond the horizon. That’s right, it is a volcano so big that it curves with the surface of the planet. 

Neutron star: A neutron star has a mass of about 1.4 times the mass of the sun, but is not much bigger than a small city, about 15 km in radius. A teaspoon of neutron star material would weigh about 10 million tons. The gravitational field is intense; the escape velocity is about 0.4 times the speed of light. The collapsed star is so dense that electrons and protons do not exist separately, but are fused to form neutrons. The outer layers form a rigid crust surrounded by an atmosphere of a highly energetic electrons and excited atoms. 

Gravitational waves: Gravitational waves are ‘ripples’ in the fabric of space-time caused by some of the most violent and energetic processes in the Universe. Albert Einstein predicted the existence of gravitational waves in 1916 in his general theory of relativity. Einstein’s mathematics showed that massive accelerating objects (such as neutron stars or black holes orbiting each other) would disrupt space-time in such a way that 'waves’ of distorted space would radiate from the source (like the movement of waves away from a stone thrown into a pond). 

Sources: Wikipedia , laspe.colorad, nasa.com, Futurism.com, LIGO & Universetoday.com

Full Moon and Jupiter sharing a field of view. 

Labeled top to bottom, the tiny pinpricks of light above bright Jupiter are the four Galilean moons; Callisto, Europa, Ganymede, and Io. Callisto, Ganymede, and Io are physically larger than Earth’s Moon, while water world Europa is only slightly smaller. In fact, of the Solar System’s six largest planetary satellites, only Saturn’s moon Titan is missing from the scene.

Image Credit & Copyright: Göran Strand

Planets: As Seen by Voyager

The Voyager 1 and 2 spacecraft explored Jupiter, Saturn, Uranus and Neptune before starting their journey toward interstellar space. Here you’ll find some of those images, including “The Pale Blue Dot” – famously described by Carl Sagan – and what are still the only up-close images of Uranus and Neptune.

These twin spacecraft took some of the very first close-up images of these planets and paved the way for future planetary missions to return, like the Juno spacecraft at Jupiter, Cassini at Saturn and New Horizons at Pluto.

Jupiter

Photography of Jupiter began in January 1979, when images of the brightly banded planet already exceeded the best taken from Earth. They took more than 33,000 pictures of Jupiter and its five major satellites. 

Findings:

  • Erupting volcanoes on Jupiter’s moon Io, which has 100 times the volcanic activity of Earth. 
  • Better understanding of important physical, geological, and atmospheric processes happening in the planet, its satellites and magnetosphere.
  • Jupiter’s turbulent atmosphere with dozens of interacting hurricane-like storm systems.

Saturn

The Saturn encounters occurred nine months apart, in November 1980 and August 1981. The two encounters increased our knowledge and altered our understanding of Saturn. The extended, close-range observations provided high-resolution data far different from the picture assembled during centuries of Earth-based studies.

Findings:

  • Saturn’s atmosphere is almost entirely hydrogen and helium.
  • Subdued contrasts and color differences on Saturn could be a result of more horizontal mixing or less production of localized colors than in Jupiter’s atmosphere.
  • An indication of an ocean beneath the cracked, icy crust of Jupiter’s moon Europa. 
  • Winds blow at high speeds in Saturn. Near the equator, the Voyagers measured winds about 1,100 miles an hour.

Uranus

The Voyager 2 spacecraft flew closely past distant Uranus, the seventh planet from the Sun. At its closest, the spacecraft came within 50,600 miles of Uranus’s cloud tops on Jan. 24, 1986. Voyager 2 radioed thousands of images and voluminous amounts of other scientific data on the planet, its moons, rings, atmosphere, interior and the magnetic environment surrounding Uranus.

Findings:

  • Revealed complex surfaces indicative of varying geologic pasts.
  • Detected 11 previously unseen moons.
  • Uncovered the fine detail of the previously known rings and two newly detected rings.
  • Showed that the planet’s rate of rotation is 17 hours, 14 minutes.
  • Found that the planet’s magnetic field is both large and unusual.
  • Determined that the temperature of the equatorial region, which receives less sunlight over a Uranian year, is nevertheless about the same as that at the poles.

Neptune

Voyager 2 became the first spacecraft to observe the planet Neptune in the summer of 1989. Passing about 3,000 miles above Neptune’s north pole, Voyager 2 made its closest approach to any planet since leaving Earth 12 years ago. Five hours later, Voyager 2 passed about 25,000 miles from Neptune’s largest moon, Triton, the last solid body the spacecraft had the opportunity to study.

Findings: 

  • Discovered Neptune’s Great Dark Spot
  • Found that the planet has strong winds, around 1,000 miles per hour
  • Saw geysers erupting from the polar cap on Neptune’s moon Triton at -390 degrees Fahrenheit

Solar System Portrait

This narrow-angle color image of the Earth, dubbed ‘Pale Blue Dot’, is a part of the first ever ‘portrait’ of the solar system taken by Voyager 1. 

The spacecraft acquired a total of 60 frames for a mosaic of the solar system from a distance of more than 4 billion miles from Earth and about 32 degrees above the ecliptic.

From Voyager’s great distance, Earth is a mere point of light, less than the size of a picture element even in the narrow-angle camera.

“Look again at that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives.” - Carl Sagan

Both spacecraft will continue to study ultraviolet sources among the stars, and their fields and particles detectors will continue to search for the boundary between the Sun’s influence and interstellar space. The radioisotope power systems will likely provide enough power for science to continue through 2025, and possibly support engineering data return through the mid-2030s. After that, the two Voyagers will continue to orbit the center of the Milky Way.

Learn more about the Voyager spacecraft HERE.

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What’s Up for April 2017

Jupiter, the king of the planets, is visible all night long, and the Lyrids meteor shower peaks on April 22.

On April 7, Jupiter–the king of planets–reaches opposition, when it shines brightest and appears largest. 

Jupiter will be almost directly overhead at midnight.

This is also a great time to observe the planet’s Galilean moons–Io, Ganymeade, Europa and Callisto. They can be easily seen through binoculars.

With binoculars, you can even see the Great Red Spot as the storm transits the planet every ten hours.

Looking east on April 22, look to the skies for the Summer Triangle, consisting of Deneb, in Cygnus, the Swan; Altair in Aquila, the Eagle; and Vega, in Lyre(the Harp).

Get ready for the Lyrids, the year’s second major meteor shower, as it pierces the Summer Triangle in the early morning hours of April 22. Since the shower begins close to the new moon, expect excellent almost moonless viewing conditions.  

You can catch up on solar system and all of our missions at www.nasa.gov

Watch the full “What’s Up for April 2017″ video: 

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What’s Up for June 2017?

Have a planet party and compare Saturn and Jupiter! We’ll show you where and when to point your telescope or binoculars to see these planets and their largest moons. 

Meet at midnight to have a planetary party when Jupiter and Saturn are visible at the same time!

The best time will be after midnight on June 17. To see the best details, you’ll need a telescope.

Saturn will be at opposition on June 15, when Saturn, the Earth and the sun are in a straight line.

Opposition provides the best views of Saturn and several of its brightest moons. At the very least, you should be able to see Saturn’s moon Titan, which is larger and brighter than Earth’s moon.

As mentioned earlier, you’ll be able to see Jupiter and Saturn in the night sky this month. Through a telescope, you’ll be able to see the cloud bands on both planets. Saturn’s cloud bands are fainter than those on Jupiter. 

You’ll also have a great view of Saturn’s Cassini Division, discovered by astronomer Giovanni Cassini in 1675, namesake of our Cassini spacecraft.

Our Cassini spacecraft has been orbiting the planet since 2004 and is on a trajectory that will ultimately plunge it into Saturn’s atmosphere on September 15, 2017, bringing the mission to a close. 

Our Juno spacecraft recently completed its sixth Jupiter flyby. Using only binoculars you can observe Jupiter’s 4 Galilean moons - Io, Callisto, Ganymede and Europa.

To learn about What’s Up in the skies for June 2017, watch the full video:

For more astronomy events, check out NASA’s Night Sky Network at https://nightsky.jpl.nasa.gov/.

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Astronomy and Astrophysics: Facts

Here is a list of some curiosities of astronomy and astrophysics. From our solar system to interstellar space.

Pluto: Pluto  is a dwarf planet in the Kuiper belt, a ring of bodies beyond Neptune. It was the first Kuiper belt object to be discovered. Like other Kuiper belt objects, Pluto is primarily made of ice and rock and is relatively small—about one-sixth the mass of the Moon and one-third its volume. It has a moderately eccentric and inclined orbit during which it ranges from 30 to 49 astronomical units or AU (4.4–7.4 billion km) from the Sun. 

Great Red Spot: The Great Red Spot is a persistent zone of high pressure, producing an anticyclonic storm on the planet Jupiter, 22° south of the equator. It has been continuously observed for 187 years, since 1830. Earlier observations from 1665 to 1713 are believed to have been the same storm; if this is correct, it has existed for more than 350 years.

Moons of Jupiter: There are 69 known moons of Jupiter. This gives Jupiter the largest number of moons with reasonably stable orbits of any planet in the Solar System. 

Uranus: Axial tilt: The Uranian axis of rotation is approximately parallel with the plane of the Solar System, with an axial tilt of 97.77° (as defined by prograde rotation). This gives it seasonal changes completely unlike those of the other planets. Near the solstice, one pole faces the Sun continuously and the other faces away. Only 

VFTS 102: VFTS 102 is a star located in the Tarantula nebula, a star forming region in the Large Magellanic Cloud, a satellite galaxy of the Milky Way.

The peculiarity of this star is its projected equatorial velocity of ~600 km/s (about 2.000.000 km/h), making it the fastest rotating massive star known. The resulting centrifugal force tends to flatten the star; material can be lost in the loosely bound equatorial regions, allowing for the formation of a disk. The spectroscopic observations seem to confirm this, and the star is classified as Oe, possibly due to emission from such an equatorial disk of gas.

Black Holes: Monsters in Space: This artist’s concept illustrates a supermassive black hole with millions to billions times the mass of our sun. Supermassive black holes are enormously dense objects buried at the hearts of galaxies. (Smaller black holes also exist throughout galaxies.) In this illustration, the supermassive black hole at the center is surrounded by matter flowing onto the black hole in what is termed an accretion disk. This disk forms as the dust and gas in the galaxy falls onto the hole, attracted by its gravity. 

Saturn’s hexagon: Saturn’s hexagon is a persisting hexagonal cloud pattern around the north pole of Saturn, located at about 78°N. The sides of the hexagon are about 13,800 km (8,600 mi) long, which is more than the diameter of Earth (about 12,700 km (7,900 mi)). 

Gravitational lens: A gravitational lens is a distribution of matter (such as a cluster of galaxies) between a distant light source and an observer, that is capable of bending the light from the source as the light travels towards the observer. This effect is known as gravitational lensing, and the amount of bending is one of the predictions of Albert Einstein’s general theory of relativity.

Quasar: A quasar is an active galactic nucleus of very high luminosity. A quasar consists of a supermassive black hole surrounded by an orbiting accretion disk of gas. As gas in the accretion disk falls toward the black hole, energy is released in the form of electromagnetic radiation. Quasars emit energy across the electromagnetic spectrum and can be observed at radio, infrared, visible, ultraviolet, and X-ray wavelengths. 

Stretching SpaceTime: According to general relativity, the sun’s mass makes an imprint on the fabric of spacetime that keeps the planets in orbit. A neutron star leaves a greater mark. But a black hole is so dense that it creates a pit deep enough to prevent light from escaping.

Source: Wikipedia, NASA & ESO 

Image credit: NASA, JPL, New Horizons, Keck Observatory, Hubble, Chandra, Kevin Gill, James Provost  

Solar System: Things to Know This Week

Almost every day, we receive a message from a spacecraft more than 10.6 billion miles (about 17 billion km) away.

At that unimaginable distance, it takes the radio signal almost 16 hours to arrive. The spacecraft is Voyager 2, which launched 40 years ago this month. It’s still operating, sending back dispatches from the dark reaches well beyond the orbit of Pluto. Even now, scientists are still actively exploring the outer boundaries of the solar system using Voyager 2, decades after its “Grand Tour” of the giant planets Jupiter, Saturn, Uranus and Neptune revealed their splendors like never before. This week, we recall 10 highlights from one of the most epic voyages in human history.

1. A Journey of 10 Billion Miles Begins With the First Step

Voyager 2 set out from Earth on Aug. 20, 1977. Even though it launched before its twin spacecraft, Voyager 1, it carried the ‘2’ moniker because mission planners knew its trajectory would bring it to Jupiter after Voyager 1’s arrival there.

2. The Grand Tour

Voyager 2’s trajectory was special because it took advantage of a rare orbital alignment to fly by all four gas giant planets: Jupiter, Saturn, Uranus and Neptune. It was the first, and so far the only, spacecraft to carry out a close-up reconnaissance of Uranus and Neptune.

3. Not-So-Gentle Giant

Voyager 2 flew by Jupiter in April 1979, capturing striking images of the planet’s volcanic moon Io and its violent storms larger than the entire Earth.

4. Saturn’s Not the Only One

Jupiter has its own ring system, and Voyager 2 provided the first pictures.

5. An Ocean Under Ice

During its Jupiter encounter, Voyager 2 obtained close-up looks at Jupiter’s moon Europa, including linear cracks and other features which first led scientists to realize Europa probably hides a vast sea of liquid water beneath an icy shell, the first known world outside Earth that could have an ocean.

6. Ringworld, the Prequel

Voyager 2 zoomed through the Saturn system in August 1981. It saw hints of mysterious features that the Cassini mission would later reveal in stunning detail, including Enceladus, with its bright surface that suggested geologic activity, and Saturn’s intriguing hexagonal jet stream.

7. Swiftly by a Tilted Planet

In January 1984, Voyager offered humanity its first detailed look at the seventh planet, Uranus, the only one tilted on its side relative to the Sun. Voyager images revealed 11 new moons, including Juliet, Puck, Cressida, Rosalind and Ophelia. The moon Miranda presented a bizarre landscape that left scientists debating its origins for years. Voyager also captured views of the planet’s lacy rings, and found that it is the coldest in the solar system, at minus 353 degrees Fahrenheit (59 Kelvin).

8. In Neptune’s Blue Realm

After picking up a gravitational speed boost at each previous planetary encounter, by the time Voyager reached Neptune it shot through the entire system of Neptunian rings and moons in a matter of hours. Voyager saw a titanic storm in Neptune’s windy atmosphere, discovered new moons, and revealed active geysers erupting on Triton’s frigid surface.

9. Postcards From the Edge

Although their cameras are no longer functioning, other key scientific instruments on board both Voyager spacecraft are still collecting data. Voyager 1 is exploring the boundary between the Sun’s realm and interstellar space. Voyager 2 hasn’t traveled quite as far. In September 2007, it crossed the termination shock (where the speed of the solar wind of charged particles drops below the speed of sound) at a point about 84 Astronomical Units from the Sun (more than twice the distance to Pluto). See https://go.nasa.gov/2uwrndb

10. Ride Along

Voyager’s mission is far from over. Engineers estimate the spacecraft will have enough power to operate into the mid-2020s. You can ride along at www.jpl.nasa.gov/voyager, or by following @NASAVoyager on Twitter and by downloading our free 3-D space simulation software, Eyes on the Solar System at eyes.nasa.gov.

One more thing: Inspired by the messages of goodwill carried on Voyager’s Golden Record, you’re invited to send a short, uplifting message to Voyager and all that lies beyond it via social media. With input from the Voyager team and a public vote, one of these messages will be selected for us to beam into interstellar space on Sept. 5, 2017—the 40th anniversary of Voyager 1’s launch. Post your message on social media with the tag #MessageToVoyager by Aug 15. Details: www.jpl.nasa.gov/voyager/message/

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