Uranus' Moon Umbriel - Universe Today Universe Today by Matt Williams The 19th century was an auspicious time for astronomers and planet hunters. In addition to the discovery of the Asteroid Belt that rests between Mars and Jupiter – as well as the many minor planets within – the outer solar planet of Uranus and its series of moons were also observed for the very first time. Of these, Umbriel was certainly one of the most interesting finds. Aside from being Uranus’ third largest moon, it is also its darkest – a trait which contributed greatly to the selection of its name. And to this day, this large satellite of Uranus is shrouded in mystery… Discovery: Umbriel, along with its fellow moon Ariel , was discovered by English astronomer William Lassell on October 24th, 1851. Fellow English astronomer William Herschel, who had discovered Uranus’ moons of Titania and Oberon at the end of the 18th century, also claimed to have observed four additional moons around Uranus. However, his observations were not confirmed, leaving the confirmed discoveries of Ariel and Umbriel to Lassell, roughly half a century later.

Naming: Much like all of Uranus’ 27 moons , Umbriel was named after a character from Alexander Pope’s The Rape of the Lock, as well as plays by William Shakespeare. These names were suggested by John Herschel, the son of William Herschel, when he announced the discoveries of Titania and Oberon. Size comparison of Earth, the Moon, and Umbriel. Credit: Tom Reding/Public Domain In keeping with the moon’s dark appearance, the name Umbriel – which was the name of the ‘dusky melancholy sprite’ in the The Rape of the Lock and is derived from the Latin Umbra (which means “shadow”) – seemed most appropriate for this satellite. Size, Mass and Orbit: Ariel and Umbriel are nearly the same size, with diameters of 1,158 kilometers and 1,170 kilometers respectively. Based on spectrograph analyses and estimates of the moon’s mass and density, astronomers believe that the majority of the planet consists of water ice, with a dense non-ice component constituting around 40% of its mass. This could mean that Umbriel consists of an icy outer shell that surrounds a rocky core, or one made out of carbonaceous materials.

It also means that though Umbriel is the third largest moon of Uranus, it is only the fourth largest in terms of mass. Furthermore, its dark appearance is believed to be the result of the interactions of surface water ice with energetic particles from Uranus’ magnetosphere. These energetic particles would cause methane deposits (trapped in the ice as clathrate hydrate) to decompose and other organic molecules to darken, leaving behind a dark, carbon-rich residue. The satellite’s dark color is also due to its very low bond albedo – which is basically the amount of electromagnetic radiation (i.e. light) that gets reflected back from the surface. So far, spectrographic analyses have only confirmed the existence of water and carbon dioxide. So the existence of organic particles or methane deposits in the ice remains theoretical. However, their presence would explain the prevalence of CO² and why it is concentrated mainly on the trailing hemisphere. Umbriel’s orbital period – i.e. the time it takes the moon to orbit Uranus – is approximately 4.1 days, which is coincident with its rotational period. This means that the moon is a synchronous and tidally-locked satellite, with one face always pointing towards Uranus.

The satellite is at an average distance of 266,000 kilometers from its planet, which makes it the third farthest from Uranus, behind Miranda and Ariel. Voyager 2: So far, the only close-up images of Umbriel have been provided by the Voyager 2 probe, which photographed the moon during its flyby of Uranus in January of 1986. During this flyby, the closest distance between Voyager 2 and Umbriel was 325,000 km (202,000 mi). The images cover about 40% of the surface, but only 20% was photographed with the quality required for geological mapping. At the time of the flyby, the southern hemisphere of Umbriel was pointed towards the Sun – so the northern, darkened hemisphere could not be studied. At present, no future missions are planned to study the moon in greater detail. US Geological Survey map of Umbriel, showing its cratered surface and polygons. Credit: ISGS Interesting Facts: The surface of Umbriel has far more and larger craters than do Ariel and Titania, ranging in diameter from a few kilometers to several hundred.

The largest known crater on the surface is Wokolo, which is 210 km in diameter. Wunda , a crater with a diameter of about 131 kilometers, is the most noticeable surface feature, due to the ring of bright material on its floor (which scientists think are from the impact). Other craters include Fin, Peri, and Zlyden which, like all of Umbriel’s surface features, are named after dark sprites from different cultures’ mythology. The only satellite of Uranus to have more craters is Oberon, and the planet is believed to be geologically stable. It is further believes that surface has probably been stable since the Late Heavy Bombardment . The only signs of ancient internal activity are canyons and dark polygons – dark patches with complex shapes measuring from tens to hundreds of kilometers across. The polygons were identified from precise photometry of Voyager 2′s images and are distributed more or less uniformly on the surface of Umbriel, trending northeast – southwest. Because Uranus orbits the Sun almost on its side, it is subject to an extreme seasonal cycle.

Both northern and southern poles spend 42 years in complete darkness, and another 42 years in continuous sunlight, with the Sun rising close to the zenith over one of the poles at each solstice. The southern hemisphere of Umbriel displays heavy cratering in this Voyager 2 image, taken Jan. 24, 1986. The large impact crater of Wunda is visible at the top. Credit: NASA/JPL Because they are in the planet’s equatorial plane, Uranus’ satellites also experience these changes. This means that Umbriel’s north and south poles spend 42 years in light and then 42 years in darkness before repeating the cycle. In fact, the Voyager 2 flyby coincided with the southern hemisphere’s 1986 summer solstice, when nearly the entire northern hemisphere was in darkness. Interesting little moon isn’t it? Even though no missions are currently planned to observe it in the coming years, one can only hope that future satellites happen to sneak a peek at it on their way to some other destination in the outer Solar System. Universe Today has many interesting articles on the moons of Uranus , like how many moons does Uranus have?

You should also check out NASA’s page on Umbriel and Uranus’ moon Umbriel at Nine Planets. Astronomy Cast has an episode on Uranus that you should check out. Sources: Uranus' moon Umbriel Uranus' moon Umbriel June 8, 2015 by Matt Williams, Universe Today Uranus and its five major moons: (left to right) Miranda, Ariel, Titania and Umbriel and Oberon in the foreground. Credit: space.com The 19th century was an auspicious time for astronomers and planet hunters. In addition to the discovery of the Asteroid Belt that rests between Mars and Jupiter – as well as the many minor planets within – the outer solar planet of Uranus and its series of moons were also observed for the very first time. Of these, Umbriel was certainly one of the most interesting finds. Aside from being Uranus' third largest moon, it is also its darkest – a trait which contributed greatly to the selection of its name.

And to this day, this large satellite of Uranus is shrouded in mystery… Discovery: Umbriel, along with its fellow moon Ariel, was discovered by English astronomer William Lassell on October 24th, 1851. Fellow English astronomer William Herschel, who had discovered Uranus' moons of Titania and Oberon at the end of the 18th century, also claimed to have observed four additional moons around Uranus. However, his observations were not confirmed, leaving the confirmed discoveries of Ariel and Umbriel to Lassell, roughly half a century later. Naming: Much like all of Uranus' 27 moons, Umbriel was named after a character from Alexander Pope's The Rape of the Lock, as well as plays by William Shakespeare. These names were suggested by John Herschel, the son of William Herschel, when he announced the discoveries of Titania and Oberon. In keeping with the moon's dark appearance, the name Umbriel – which was the name of the 'dusky melancholy sprite' in the The Rape of the Lock and is derived from the Latin Umbra (which means "shadow") – seemed most appropriate for this satellite.

Size, Mass and Orbit: Ariel and Umbriel are nearly the same size, with diameters of 1,158 kilometers and 1,170 kilometers respectively. Based on spectrograph analyses and estimates of the moon's mass and density, astronomers believe that the majority of the planet consists of water ice, with a dense non-ice component constituting around 40% of its mass. Size comparison of Earth, the Moon, and Umbriel. Credit: Tom Reding/Public Domain This could mean that Umbriel consists of an icy outer shell that surrounds a rocky core, or one made out of carbonaceous materials. It also means that though Umbriel is the third largest moon of Uranus, it is only the fourth largest in terms of mass. Furthermore, its dark appearance is believed to be the result of the interactions of surface water ice with energetic particles from Uranus' magnetosphere. These energetic particles would cause methane deposits (trapped in the ice as clathrate hydrate) to decompose and other organic molecules to darken, leaving behind a dark, carbon-rich residue. The satellite's dark color is also due to its very low bond albedo – which is basically the amount of electromagnetic radiation (i.e.

light) that gets reflected back from the surface. So far, spectrographic analyses have only confirmed the existence of water and carbon dioxide. So the existence of organic particles or methane deposits in the ice remains theoretical. However, their presence would explain the prevalence of CO² and why it is concentrated mainly on the trailing hemisphere. Umbriel's orbital period – i.e. the time it takes the moon to orbit Uranus – is approximately 4.1 days, which is coincident with its rotational period. This means that the moon is a synchronous and tidally-locked satellite, with one face always pointing towards Uranus. The satellite is at an average distance of 266,000 kilometers from its planet, which makes it the third farthest from Uranus, behind Miranda and Ariel. Voyager 2: So far, the only close-up images of Umbriel have been provided by the Voyager 2 probe, which photographed the moon during its flyby of Uranus in January of 1986. During this flyby, the closest distance between Voyager 2 and Umbriel was 325,000 km (202,000 mi).

The images cover about 40% of the surface, but only 20% was photographed with the quality required for geological mapping. At the time of the flyby, the southern hemisphere of Umbriel was pointed towards the sun – so the northern, darkened hemisphere could not be studied. At present, no future missions are planned to study the moon in greater detail. The video will load shortly Interesting Facts: The surface of Umbriel has far more and larger craters than do Ariel and Titania, ranging in diameter from a few kilometers to several hundred. The largest known crater on the surface is Wokolo, which is 210 km in diameter. Wunda, a crater with a diameter of about 131 kilometers, is the most noticeable surface feature, due to the ring of bright material on its floor (which scientists think are from the impact). Other craters include Fin, Peri, and Zlyden which, like all of Umbriel's surface features, are named after dark sprites from different cultures' mythology. The only satellite of Uranus to have more craters is Oberon, and the planet is believed to be geologically stable.

It is further believed that surface has probably been stable since the Late Heavy Bombardment. The only signs of ancient internal activity are canyons and dark polygons – dark patches with complex shapes measuring from tens to hundreds of kilometers across. The polygons were identified from precise photometry of Voyager 2′s images and are distributed more or less uniformly on the surface of Umbriel, trending northeast – southwest. US Geological Survey map of Umbriel, showing its cratered surface and polygons. Credit: ISGS Because Uranus orbits the sun almost on its side, it is subject to an extreme seasonal cycle. Both northern and southern poles spend 42 years in complete darkness, and another 42 years in continuous sunlight, with the sun rising close to the zenith over one of the poles at each solstice. Because they are in the planet's equatorial plane, Uranus' satellites also experience these changes. This means that Umbriel's north and south poles spend 42 years in light and then 42 years in darkness before repeating the cycle. In fact, the Voyager 2 flyby coincided with the southern hemisphere's 1986 summer solstice, when nearly the entire northern hemisphere was in darkness. Interesting little moon isn't it?

Even though no missions are currently planned to observe it in the coming years, one can only hope that future satellites happen to sneak a peek at it on their way to some other destination in the outer solar system. The southern hemisphere of Umbriel displays heavy cratering in this Voyager 2 image, taken Jan. 24, 1986. The large impact crater of Wunda is visible at the top. Credit: NASA/JPL Uranus’ Moon of Umbriel - Technology Org Technology Org Uranus’ Moon of Umbriel Posted June 8, 2015 The 19th century was an auspicious time for astronomers and planet hunters. In addition to the discovery of the Asteroid Belt that rests between Mars and Jupiter – as well as the many minor planets within – the outer solar planet of Uranus and its series of moons were also observed for the very first time. Uranus and its five major moons: (left to right) Miranda, Ariel, Titania and Umbriel and Oberon in the foreground. Credit: space.com Of these, Umbriel was certainly one of the most interesting finds.

Aside from being Uranus’ third largest moon, it is also its darkest – a trait which contributed greatly to the selection of its name. And to this day, this large satellite of Uranus is shrouded in mystery… Discovery: Umbriel, along with its fellow moon Ariel , was discovered by English astronomer William Lassell on October 24th, 1851. Fellow English astronomer William Herschel, who had discovered Uranus’ moons of Titania and Oberon at the end of the 18th century, also claimed to have observed four additional moons around Uranus. However, his observations were not confirmed, leaving the confirmed discoveries of Ariel and Umbriel to Lassell, roughly half a century later. Naming: Much like all of Uranus’ 27 moons , Umbriel was named after a character from Alexander Pope’s The Rape of the Lock, as well as plays by William Shakespeare. These names were suggested by John Herschel, the son of William Herschel, when he announced the discoveries of Titania and Oberon. Size comparison of Earth, the Moon, and Umbriel.

Credit: Tom Reding/Public Domain In keeping with the moon’s dark appearance, the name Umbriel – which was the name of the ‘dusky melancholy sprite’ in the The Rape of the Lockand is derived from the Latin Umbra (which means “shadow”) – seemed most appropriate for this satellite. Size, Mass and Orbit: Ariel and Umbriel are nearly the same size, with diameters of 1,158 kilometers and 1,170 kilometers respectively. Based on spectrograph analyses and estimates of the moon’s mass and density, astronomers believe that the majority of the planet consists of water ice, with a dense non-ice component constituting around 40% of its mass. This could mean that Umbriel consists of an icy outer shell that surrounds a rocky core, or one made out of carbonaceous materials. It also means that though Umbriel is the third largest moon of Uranus, it is only the fourth largest in terms of mass. Furthermore, its dark appearance is believed to be the result of the interactions of surface water ice with energetic particles from Uranus’ magnetosphere.

These energetic particles would cause methane deposits (trapped in the ice as clathrate hydrate) to decompose and other organic molecules to darken, leaving behind a dark, carbon-rich residue. The satellite’s dark color is also due to its very low bond albedo – which is basically the amount of electromagnetic radiation (i.e. light) that gets reflected back from the surface. So far, spectrographic analyses have only confirmed the existence of water and carbon dioxide. So the existence of organic particles or methane deposits in the ice remains theoretical. However, their presence would explain the prevalence of CO² and why it is concentrated mainly on the trailing hemisphere. Umbriel’s orbital period – i.e. the time it takes the moon to orbit Uranus – is approximately 4.1 days, which is coincident with its rotational period. This means that the moon is a synchronous and tidally-locked satellite, with one face always pointing towards Uranus. The satellite is at an average distance of 266,000 kilometers from its planet, which makes it the third farthest from Uranus, behind Miranda and Ariel.

Voyager 2: So far, the only close-up images of Umbriel have been provided by the Voyager 2 probe, which photographed the moon during its flyby of Uranus in January of 1986. During this flyby, the closest distance between Voyager 2and Umbriel was 325,000 km (202,000 mi). The images cover about 40% of the surface, but only 20% was photographed with the quality required for geological mapping. At the time of the flyby, the southern hemisphere of Umbriel was pointed towards the Sun – so the northern, darkened hemisphere could not be studied. At present, no future missions are planned to study the moon in greater detail. US Geological Survey map of Umbriel, showing its cratered surface and polygons. Credit: ISGS Interesting Facts: The surface of Umbriel has far more and larger craters than do Ariel and Titania, ranging in diameter from a few kilometers to several hundred. The largest known crater on the surface is Wokolo, which is 210 km in diameter.

Wunda , a crater with a diameter of about 131 kilometers, is the most noticeable surface feature, due to the ring of bright material on its floor (which scientists think are from the impact). Other craters include Fin, Peri, and Zlyden which, like all of Umbriel’s surface features, are named after dark sprites from different cultures’ mythology. The only satellite of Uranus to have more craters is Oberon, and the planet is believed to be geologically stable. It is further believes that surface has probably been stable since the Late Heavy Bombardment . The only signs of ancient internal activity are canyons and dark polygons – dark patches with complex shapes measuring from tens to hundreds of kilometers across. The polygons were identified from precise photometry of Voyager 2′s images and are distributed more or less uniformly on the surface of Umbriel, trending northeast – southwest. Because Uranus orbits the Sun almost on its side, it is subject to an extreme seasonal cycle. Both northern and southern poles spend 42 years in complete darkness, and another 42 years in continuous sunlight, with the Sun rising close to the zenith over one of the poles at each solstice.

The southern hemisphere of Umbriel displays heavy cratering in this Voyager 2 image, taken Jan. 24, 1986. The large impact crater of Wunda is visible at the top. Credit: NASA/JPL Because they are in the planet’s equatorial plane, Uranus’ satellites also experience these changes. This means that Umbriel’s north and south poles spend 42 years in light and then 42 years in darkness before repeating the cycle. In fact, the Voyager 2 flyby coincided with the southern hemisphere’s 1986 summer solstice, when nearly the entire northern hemisphere was in darkness. Interesting little moon isn’t it? Even though no missions are currently planned to observe it in the coming years, one can only hope that future satellites happen to sneak a peek at it on their way to some other destination in the outer Solar System.

Source: Universe Today , written by Matt Williams Related Topics: The Discovery of the Uranus Moons Ariel and Umbriel - yovisto Blogyovisto Blog You are here: Home › astronomy › The Discovery of the Uranus Moons Ariel and Umbriel The Discovery of the Uranus Moons Ariel and Umbriel 0 Tabea Tietz Montage of Uranus‘ five largest satellites from left to right: Miranda, Ariel, Umbriel, Titania and Oberon. Images are presented to show correct relative sizes and brightness. Coverage is incomplete for Miranda and Ariel; gray circles depict missing areas On October 24, 1851, English merchant and astronomer William Lassell discovered Ariel and Umbriel, two moons of planet Uranus. Besides, he also discovered the Neptune moon Triton and the Saturn moon Hyperion. William Lassell was born in Bolton and educated in Rochdale. He was apprenticed to a merchant in Liverpool and later became a beer brewer and hobby astronomer.

Lassell built himself an observatory in West Derby, a suburb of Liverpool with a 610mm reflector telescope for which he pioneered the use of an equatorial mount for easy tracking of objects as the Earth rotates. Around 1854 the observatory was moved to Bradstone. Already in 1846, William Lassell discovered thr largest moon of Neptune, Triton, 17 days after the discovery of Neptune itself by Johann Gottfried Galle. Two years later, independently co-discovered Hyperion, a moon of Saturn. Both Ariel and the slightly larger Uranian satellite Umbriel were discovered by William Lassell on 24 October 1851. Although William Herschel, who discovered Uranus’s two largest moons Titania and Oberon in 1787, claimed to have observed four additional moons, however this was never confirmed and those four objects are now thought to be spurious. All of Uranus’s moons are named after characters from the works of William Shakespeare or Alexander Pope’s The Rape of the Lock. The names of all four satellites of Uranus then known were suggested by John Herschel in 1852 at the request of Lassell.

Ariel is named after the leading sylph in The Rape of the Lock. It is also the name of the spirit who serves Prospero in Shakespeare’s The Tempest. In total, Uranus has 27 known natural satellites and along with Ariel and Umbriel, Miranda, Titania, and Oberon belong to the five main satellites. The Uranian satellite system is the least massive among those of the giant planets and it is believed that the combined mass of Uranus’ five major satellites would be less than half that of Triton, the largest moon of Neptune, alone. Among the Uranian satellites, Ariel appears to have the youngest surface with the fewest impact craters and Umbriel’s the oldest. References and Further Reading: Astronomy for Kids - The Moons of Uranus Please click here for more information. The Five Largest Moons of Uranus Image courtesy of: NASA-Voyager mission Currently, we know that Uranus has at least twenty-one moons. The above image is a "family portrait" of the five largest moons of the planet. From left to right, they are Miranda, Ariel, Umbriel, Titania and Oberon.

The Voyager mission discovered ten more moons when it visited the planet in 1986 and since then, astronomers have discovered six more. Image courtesy of: NASA - Voyager mission Miranda Although it is the smallest of the five larger moons of Uranus, Miranda nonetheless has presented us with a number of puzzles. If you look closely at the picture at the right, you will notice that about half of the moon looks like a lot of the other moons in our solar system. It has lots of craters that tell us that it has been hit by many objects during its long life. The other half of the moon is covered by what appear to be giant cliffs, grooves, gullies and other features a lot like you might find in the American West, although much, much larger. What has caused all of these unusual features? In all honesty, nobody really knows, and the only we will find out is to send another spacecraft to the distant planet for an extended visit. Image courtesy of: NASA The half of Miranda that is covered with canyons, valleys and giant ridges is the most interesting part of this tiny world. Among the fascinating features of this region is the giant cliff shown in the picture at right.

Although the moon is a little under three hundred miles in diameter, the ridge shown in the picture is taller than Mount Everest here on Earth. How did such a small world become the home of such a large cliff? It is one of the many questions that remain unanswered. Image courtesy of: NASA - Voyager mission Ariel The second of the large Moons of Uranus is Ariel. Ariel, with a diameter of almost 720 miles, is much larger than Miranda and is made up mostly of rocky material and ice. The pictue at right shows an interesting world that one side has lots of craters much like our own Moon, but the other side is criss-crossed by what appear to be large grooves of some kind. What causes such unusual features? One explanation may be that at some time in the distant past Ariel might have been much warmer than it is now. If this is the case, some of the ice in the moon may have melted and smoothed out the surface of the moon and then more recent geological activity may have formed the long, wide grooves we see in the picture. Once again, it's a question that only extended research will provide the answer to.

Image courtesy of: NASA - Voyager mission Umbriel The third in the family of the five largest moons of Uranus is Umbriel. Although Umbriel is about the same size as Ariel, the family resemblance ends there. Where Ariel shows us a face that has lots of interesting and mysterious features, Umbriel is more like what most moons look like. It does have lots of impact craters, but other than that, it's a pretty cold, plain place. The only really interesting feature of this moon is the bright crater you can see at the top of the picture at the right. This crater is very large, almost seventy miles across, and is also very bright, compared to the surface of the rest of the moon. Does the interior of this moon contain material that is actually much lighter in color or was the crater just created recently? Either of these would provide an explanation as to why the crater is so much brighter than the rest of the surface. Image courtesy of: NASA - Voyager mission Titania At a little over 980 miles in diameter, Titania is the largest moon of Uranus, as befits its name. Like the other moons of the planet that we have seen, Titania is made up of rocks and ice.

Another thing that Titania has in common with its family members is the fact that part of its surface is heavily cratered, and part of it has lots of ridges, gullies and other features that look like erosion features that we see here on Earth and on Mars. What special set of circumstances have occurred during the planet's history could have caused this? Hopefully, some future mission to the planet will provide answers to the many questions we have. Image courtesy of: NASA - Voyager mission Oberon The last of the largest moons of Uranus is Oberon. At a little over 945 miles in diameter, this moon is just a little smaller than Titania. What Oberon doesn't have that its other family members have is a region that is covered with ridges and gullies. This moon is almost entirely covered by impact craters, much like most of the other moons in the solar system. If you look closely, though, at the bottom left hand side of the image you can just barely make out what appears to be a "mountain" rising from the surface of the moon. This mountain is over three miles high and is the most interesting feature on the surface of this moon.

Facts About Umbriel: Uranus' Moon Interesting Facts about Umbriel, One of the Moons of Uranus written by: Andy Dziuba•edited by: RC Davison •updated: 8/29/2010 Uranus, the second furthest planet from the Sun, has five large moons. Umbriel, discovered centuries ago, stood out in stark contrast from the others when NASA sent the Voyager 2 probe to explore the outer solar system. slide 1 of 3 Umbriel With the advent of the dwarf planet, Uranus now sits as the second furthest planet from the Sun. In an odd twist, the 27 moons of Uranus have been named after characters from the works of English playwrights Alexander Pope and William Shakespeare. The first moons to be discovered were in 1787 by William Herschel, and would not receive names for nearly a hundred years. On October 24, 1851 another English astronomer named William Lassell discovered two more moons around Uranus, which would become Ariel and Umbriel. Umbriel was named after a spirit in Alexander Pope's The Rape of Lock.

For another century astronomy went on without knowing very much more about Umbriel. The space age exploded onto the world in the mid 20th century, and we finally were able to get a better look at the moons of Uranus. In January 1986 the Voyager 2 probe was sent into the far reaches of the solar system and made a pass by Uranus. The probe made some interesting discoveries when scientists at NASA pointed its camera at Umbriel. First and foremost, Umbriel is dark. Compared to the other moons of Uranus like Ariel, Umbriel only reflect about half of the amount of light. On top of that, images of Umbriel showed a mysterious bright ring about 140 kilometers in diameter at one of its poles. To this day astronomers have not been able to definitively explain these characteristics of Umbriel, although there is speculation that the white ring is a frost deposit associated with an impact crater. Umbriel itself is made up of roughly equal parts of rock and ice. It is the fourth largest, and third most distant of Uranus' five large moons. Like most other moons, including the Earth's moon, Umbriel is tidally locked with the planet that it orbits.

This means that Umbriel always shows the same face to Uranus. The Voyager 2 probe has been the only object to study Umbriel up close, and took several pictures that allowed mapping of roughly 40% of its surface. Since Uranus orbits the Sun nearly on its side and Umbriel orbits Uranus on its equatorial plane, it has extreme seasonal cycles. Both Umbriel's northern and southern poles go through 42 years of darkness and 42 years of light. slide 2 of 3 Facts About Umbriel Radius: 584.7 km (363.3 miles) Mass: 1.7 x1021 kg (3.7 x1021 pounds) Distance from Uranus: 265, 998 km (165,277 miles) Orbital Period: 4.14 Earth days Orbital Eccentricity: 0.0050 Orbital Inclination to Ecliptic: 0.36 degree Surface Albedo: 10% - 15% Umbriel Moon | PlanetsEdu.com Umbriel is one of Uranus’ moons.

It was discovered in 1851 by British astronomer William Lassell. Diameter: 1.17 x 106 m Mass: 1.27 x 1021 kg Composition: Ice and rock Orbit: 2.66 x 108 m from Uranus Umbriel is the third largest of Uranus’ moons. 15 moons orbiting Uranus are known to exist; the largest five were discovered by observations from Earth, and the 10 smaller moons were discovered later by spacecraft missions. All of Uranus’ moons are named after characters from either William Shakespeare or Alexander Pope. Umbriel takes its name from Pope’s poem “The Rape of the Lock”. Etymologically, Umbriel’s name comes from the Latin word “umbra”, meaning shadow. This is fitting as Umbriel is the darkest moon orbiting Uranus. It is much less reflective of the Sun’s light than Ariel, another of Uranus’ moons which was discovered at the same time, also by Lassell. In composition Umbriel has a core of rock and an icy mantle. It has recognisable surface features such as its numerous overlapping impact craters.

These were caused by violent collisions which were frequent in the early stages of our solar system when Umbriel was formed. They also provide evidence that the surface structure of Umbriel has not changed significantly since the time of its formation. Some of the most significant craters are named and catalogued; the largest, Wokolo, measures 210km in diameter. Another striking feature is Wunda, a crater which appears as a ring of very bright material near Umbriel’s equator. Umbriel orbits Uranus in its equatorial plane and revolves in the same direction as the planet’s rotation. Umbriel’s orbital period is the same as its rotational period, at roughly four Earth days. This means that the same side of Umbriel is always facing towards Uranus. Along with Uranus and its other satellites, Umbriel takes around 84 Earth years to orbit the sun. In 1986 the Voyager 2 spacecraft mission travelled past Uranus and took photos of Umbriel and other moons. Despite the technical difficulty associated with imaging moving objects whilst travelling past them, Voyager 2 was able to collect images of Umbriel with an impressive resolution of about 3km.

This has been the only mission to Uranus and its moons to date. Share this with the Universe! Umbriel Gallery Close view of Umbriel taken by Voyager on January 24th 1986 Uranus' five largest satellites, ordered in distance from the planet, to scale in size and brightness. Ariel can be seen at the top right Umbriel (moon) | Gravity Wiki | Fandom powered by Wikia Template:Bots Umbriel is a moon of Uranus discovered on October 24, 1851, by William Lassell . It was discovered at the same time as Ariel and named after a character in the Alexander Pope 's poem The Rape of the Lock . Umbriel consists mainly of ice with a substantial fraction of rock , and may be differentiated into a rocky core and an icy mantle . The surface is the darkest among Uranian moons, and appears to have been shaped primarily by impacts. However, the presence of canyons suggests early endogenic processes, and the moon may have undergone an early endogenically driven resurfacing event that obliterated its older surface.

Covered by numerous impact craters reaching 210 km (130 mi) in diameter, Umbriel is the second most heavily cratered satellite of Uranus after Oberon . The most prominent surface feature is a ring of bright material on the floor of Wunda crater. This moon, like all moons of Uranus, probably formed from an accretion disk that surrounded the planet just after its formation. The Uranian system has been studied up close only once: by the spacecraft Voyager 2 in January 1986. It took several images of Umbriel, which allowed mapping of about 40% of the moon’s surface. Contents Edit Umbriel, along with another Uranian satellite Ariel , was discovered by William Lassell on October 24, 1851. [1] [2] Although William Herschel , the discoverer of Titania and Oberon , claimed at the end of the 18th century that he had observed four additional moons of Uranus, [3] his observations were not confirmed and those four objects are now thought to be spurious. [4] All Uranus's moons are named after characters created by William Shakespeare or Alexander Pope .

The names of all four satellites of Uranus then known were suggested by John Herschel in 1852 at the request of Lassell. [5] Umbriel is the 'dusky melancholy sprite' in Alexander Pope's The Rape of the Lock , [6] and the name suggests the Latin umbra , meaning shadow. The moon is also designated Uranus II. [2] Orbit Edit Umbriel orbits Uranus at the distance of about 266,000 km (165,000 mi), being the third farthest from the planet among its five major moons . [note 1] Umbriel's orbit has a small eccentricity and is inclined very little relative to the equator of Uranus. [7] Its orbital period is around 4.1 Earth days, coincident with its rotational period . In other words, Umbriel is a synchronous or tidally locked satellite, with one face always pointing toward the planet. [8] Umbriel's orbit lies completely inside the Uranian magnetosphere .

[9] This is important, because the trailing hemispheres of airless satellites orbiting inside a magnetosphere (like Umbriel ) are struck by magnetospheric plasma , which co-rotates with the planet. [10] This bombardment may lead to the darkening of the trailing hemispheres, which is actually observed for all Uranian moons except Oberon (see below). [9] Umbriel also serves as a sink of the magnetospheric charged particles, which creates a pronounced dip in energetic particle count near the moon's orbit as observed by Voyager 2 in 1986. [11] Because Uranus orbits the Sun almost on its side, and its moons orbit in the planet's equatorial plane, they (including Umbriel) are subject to an extreme seasonal cycle. Both northern and southern poles spend 42 years in complete darkness, and another 42 years in continuous sunlight. [9] Once every 42 years, when Uranus has an equinox and its equatorial plane intersects the Earth, mutual occultations of Uranus's moons become possible.

In 2007–2008 a number of such events was observed including two occultations of Titania by Umbriel on August 15 and December 8, 2007 as well as of Ariel by Umbriel on August 19, 2007. [12] Currently Umbriel is not involved in any orbital resonance with other Uranian satellites. In the past, however, it may have been in the 3:1 resonance with Miranda , which was partially responsible for the heating of that moon. [13] Composition and internal structure Edit Umbriel is the third largest and fourth most massive of Uranian moons. [note 2] The moon's density is 1.39 g/cm3, [15] which indicates that it mainly consists of water ice , while a dense non-ice component constitutes around 40% of its mass. [16] The latter could be made of rock and carbonaceous material including heavy organic compounds known as tholins . [8] The presence of water ice is supported by infrared spectroscopic observations, which have revealed crystalline water ice on the surface of the moon.

[9] Water ice absorption bands are stronger on Umbriel's leading hemisphere than on the trailing hemisphere. [9] The cause of this asymmetry is not known, but it may be related to the bombardment by charged particles from the magnetosphere of Uranus , which is stronger on the trailing hemisphere (due to the plasma's co-rotation). [9] The energetic particles tend to sputter water ice, decompose methane trapped in ice as clathrate hydrate and darken other organics, leaving a dark, carbon-rich residue behind. [9] Except for water, the only other compound identified on the surface of Umbriel by the infrared spectroscopy is carbon dioxide , which is concentrated mainly on the trailing hemisphere. [9] The origin of the carbon dioxide is not completely clear. It might be produced locally from carbonates or organic materials under the influence of the energetic charged particles coming from the magnetosphere of Uranus or the solar ultraviolet radiation. This hypothesis would explain the asymmetry in its distribution, as the trailing hemisphere is subject to a more intense magnetospheric influence than the leading hemisphere. Another possible source is the outgassing of the primordial CO2 trapped by water ice in Umbriel's interior.

The escape of CO2 from the interior may be related to the past geological activity on this moon. [9] Umbriel may be differentiated into a rocky core surrounded by an icy mantle . [16] If this is the case, the radius of the core (317 km) is about 54% of the radius of the moon, and its mass is around 40% of the moon’s mass—the parameters are dictated by the moon's composition. The pressure in the center of Umbriel is about 0.24 GPa (2.4 kbar ). [16] The current state of the icy mantle is unclear, although the existence of the subsurface ocean is considered unlikely. [16] Surface features File:Umbriel usgs.jpg Umbriel's surface is the darkest of the Uranian moons, and reflects less than half as much light as Ariel, a sister satellite of similar size. [14] Umbriel has a very low bond albedo of only about 10% as compared to 23% for Ariel.

[17] The reflectivity of the moon's surface decreases from 26% at a phase angle of 0° ( geometrical albedo ) to 19% at an angle of about 1°. This phenomenon is called opposition surge . Opposite to what is observed for another dark Uranian moon, Oberon, the surface of Umbriel is slightly blue in color, [18] while fresh bright impact deposits (in Wunda crater, for instance) [19] are even bluer. There may be an asymmetry between the leading and trailing hemispheres; the former appears to be redder than the latter. [20] The reddening of the surfaces probably results from space weathering from bombardment by charged particles and micrometeorites over the age of the Solar System . [18] On the other hand, the color asymmetry is more likely caused by accretion of a reddish material coming from outer parts of the Uranian system, possibly, from irregular satellites , which would occur predominately on the leading hemisphere. [20] The surface of Umbriel is relatively homogeneous—it does not demonstrate strong variation in either albedo or color.

[18] Scientists have so far recognized only one class of geological feature on Umbriel— craters . [21] The surface of Umbriel has far more and larger craters than do Ariel and Titania and is also the least geologically active. [19] In fact only Oberon has more impact craters than Umbriel. The observed crater diameters range from a few kilometers at the low end to 210 kilometers for the largest known crater, Wokolo. [19] [21] All recognized craters on Umbriel have central peaks, [19] but no crater has rays . [8] Template:Coord/input/d 44.0 Near Umbriel's equator lies the most prominent surface feature: Wunda crater, which has a diameter of about 131 km. [23] [24] Wunda has a large ring of bright material on its floor, which appears to be an impact deposit. [19] Nearby, seen along the terminator , are the craters Vuver and Skynd , which lack bright rims but possess bright central peaks.

[8] [24] Study of limb profiles of Umbriel revealed a possible very large impact feature having the diameter of about 400 km and depth of approximately 5 km. [25] Much like other moons of Uranus, the surface of Umbriel is cut by a system of canyons trending northeast–southwest. [26] They are not, however, officially recognized due to the poor resolution of images and generally bland appearance of this moon, which hinders geological mapping . [19] Umbriel's heavily cratered surface has probably been stable since the Late Heavy Bombardment . [19] The only signs of the ancient internal activity are canyons and dark polygons—dark patches with complex shapes measuring from tens to hundreds kilometers across. [27] The polygons were identified from the precise photometry of Voyager's images and are distributed more or less uniformly on the surface of Umbriel trending northeast–southwest. Some polygons correspond to depressions of a few kilometers deep and may have been created during an early episode of tectonic activity. [27] Currently there is no explanation of why Umbriel is so dark and uniform in appearance.

Its surface may be covered by a relatively thin layer of dark material (so called umbral material) excavated by an impact or expelled in an explosive volcanic eruption. [note 3] [20] Alternatively, Umbriel's crust may be entirely composed of the dark material, which prevented formation of bright features like crater rays. However, the presence of the bright Wunda feature seems to contradict this hypothesis. [8] Origin and evolution Edit Umbriel is thought to have formed from an accretion disc or subnebula; a disc of gas and dust that either existed around Uranus for some time after its formation or was created by the giant impact that most likely gave Uranus its large obliquity . [28] The precise composition of the subnebula is not known; however, the higher density of Uranian moons compared to the moons of Saturn indicates that it may have been relatively water-poor. [note 4] [8] Significant amounts of nitrogen and carbon may have been present in the form of carbon monoxide (CO) and molecular nitrogen (N2) instead of ammonia and methane.

[28] The moons that formed in such a subnebula would contain less water ice (with CO and N2 trapped as clathrate) and more rock, explaining the higher density. [8] Umbriel's accretion probably lasted for several thousand years. [28] The impacts that accompanied accretion caused heating of the moon's outer layer. [29] The maximum temperature of around 180 K was reached at the depth of about 3 km. [29] After the end of formation, the subsurface layer cooled, while the interior of Umbriel heated due to decay of radioactive elements present in its rocks. [8] The cooling near-surface layer contracted, while the interior expanded. This caused strong extensional stresses in the moon's crust, which may have led to cracking. [30] The present-day canyons may be a result of this process, [26] which lasted for about 200 million years, implying that any endogenous activity ceased billions years ago.

[8] The initial accretional heating together with continued decay of radioactive elements may have led to melting of the ice [29] if an antifreeze like ammonia (in the form of ammonia hydrate ) or some salt was present. [16] The melting may have led to the separation of ice from rocks and formation of a rocky core surrounded by an icy mantle. [19] A layer of liquid water (ocean) rich in dissolved ammonia may have formed at the core–mantle boundary. The eutectic temperature of this mixture is 176 K. The ocean, however, is likely to have frozen long ago. [16] Among Uranian moons Umbriel was least subjected to endogenic resurfacing processes, [19] although it may like other Uranian moons have experienced a very early resurfacing event. [27] Exploration Edit Template:Mainarticle So far the only close-up images of Umbriel have been from the Voyager 2 probe, which photographed the moon during its flyby of Uranus in January 1986.

Since the closest distance between Voyager 2 and Umbriel was 325,000 km (202,000 mi), [31] the best images of this moon have a spatial resolution of about 5.2 km. [19] The images cover about 40% of the surface, but only 20% was photographed with the quality required for geological mapping . [19] At the time of the flyby the southern hemisphere of Umbriel (like those of the other moons) was pointed towards the Sun, so the northern (dark) hemisphere could not be studied. [8] No other spacecraft has ever visited Uranus (and Umbriel), and no mission to this planet is planned. Notes Edit ↑ The five major moons are Miranda , Ariel , Umbriel, Titania and Oberon. ↑ Due to the current observational error , it is not yet known for certain whether Ariel is more massive than Umbriel. [14] ↑ While a co-orbiting population of dust particles is another possible source of the dark material, this is considered less likely because other satellites were not affected.

[8] ↑ For instance, Tethys , a Saturnian moon, has the density of 0.97 g/cm3, which means that it contains more than 90% of water.

[9] References ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Lassell1851 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Lassell1851b ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Herschel3 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Struve1848 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Lassell5 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Kuiper1949 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named orbit ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Smith1986 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Grundy2006 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Ness1986 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Krim

igis1986 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named occultations ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Tittemore1990 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named JPLSSD ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Jacobson1992 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Hassmann2006 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Karkoschka2001a ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Bell1991 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Plescia1987 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Buratti1991 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named usgs ↑ Cite error: Invalid <ref> tag; no text was provided

 for refs named Strobell1987 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named usgsWunda ↑ Cite error: Invalid <ref> tag; no text was provided for refs named hunt ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Moore2004 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Croft1989 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Helfenstein1989 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Mousis2004 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Squyres1988 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Hillier1991 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Stone1987 External links BW Color Prints | Science On a Sphere - Datasets Uranus’ Moons — Miranda, Ariel, Umbriel, Titania, Oberon Description: Uranus has

 27 moons, all of which are named after characters in Shakespeare and Alexander Pope works.

The five main satellites, in order of proximity to Uranus, are Miranda, Ariel, Umbriel, Titania, and Oberon. Before the Voyager 2 studied Uranus in 1986, these five moons were the only ones known to exist. Miranda Miranda (a character in The Tempest by Shakespeare) has a surface unlike any other in the solar system. One theory for the jumbled appearance is that the moon has shattered and reformed up to five times, creating a surface of both young and old material. Another explanation involves the upwelling of partially melted ices. Ariel Ariel (a character in The Tempest by Shakespeare and also a character in a Pope poem) is the brightest moon of Uranus. The most notable features on this moon are the craters that cover the surface as well as the interconnected rift valleys that run across the moon. Some of the valleys are up to 6 miles deep. Umbriel Umbriel (a character in The Rape of the Lock by Pope) is the darkest moon of Uranus. It is also the least geologically active satellite with a heavily cratered surface indicating that it is old.

Near the equator of Umbriel is a bright ring referred to the as the Fluorescent Cheerio or Wunda. The origin of this is unknown, though it is believed to be the floor of a crater. Titania Titania (Queen of the fairies in A Midsummer Night’s Dream by Shakespeare) has a surface remarkably similar to that of Ariel. Covered in craters and interconnected valleys like Ariel, Titania is 35% larger than Ariel and is the largest of the known satellites orbiting Uranus. One of the most notable features is a trench that extends for over 1000 miles. It is thought that the satellite was once hot and the valleys and trenches are the result of the planet freezing and expanding. Oberon Oberon (King of the fairies in A Midsummer Night’s Dream by Shakespeare) is similar to Umbriel but 35% larger. Heavily cratered and geologically inactive, Oberon is the second largest moon of Uranus. In many of the large craters that cover the surface there is a dark material that coats the crater floors. It is still unknown what causes this. Also of interest on Oberon is a mountain that is over 4 miles tall.

Data Category Umbriel Uranus's Blue Moon Umbriel Uranus’s Blue Moon [adsense] Uranus’s Moon Umbriel A dark, somewhat blue sphere, is on a continuous journey around the Icy Giant, Uranus. Despite being photographed up close once and the great distance of over two billion kilometres that separates us – we have quite a good picture of what the world of Uranus’s moon Umbriel looks like. Umbriel, the darkest of all the Uranian moons was named after a character in the poem The Rape of the Lock by Alexander Pope. Uranus’s Moon Umbriel: A Sub-Zero World Taking just over four days to complete one trip around Uranus, Umbriel orbits the planet at a distance of 266,000 kilometres (165,000 miles). Uranus’s moon Umbriel is a very cold world with an average surface temperature of minus 198 degrees Celsius (minus 324 degrees Fahrenheit). Like many other moons in the Solar System, including our own Moon , Uranus’s moon Umbriel is tidally locked. This means that one side continually faces Uranus while the other is always pointing away from the planet.

Uranus’s moon Umbriel is comprised mostly of ice though it is thought to have rocky core and an icy mantle. The density of Umbriel indicates that the moon is comprised of 60 per cent water ice and 40 per cent non-ice. The non-ice component is thought to be a combination of rock and carbonaceous material. 42-Year Seasons Uranus’s moon Umbriel’s orbit resides completely within the magnetsphere of the planet which means the moon is subject to magnetsopheric plasma which has resulted in the darkening of its trailing hemisphere. Like Oberon, Uranus’s Umbriel has an extraordinarily extreme seasonal cycle. The poles of the moon spend 42 years in either complete darkness or continuous sunlight. Presence Of Carbon Dioxide Carbon dioxide has been observed to be present on the moon’s surface. Although its origins are not fully understood several possible hypotheses have been offered as an explanation. One is that the carbon dioxide is being formed through either organic material or carbonates being bombarded by either charged particles or ultraviolet radiation emanating from the Sun. The second explanation is that primordial carbon dioxide once trapped in the ice is escaping from Uranus’s moon Umbriel.

Uranus’s Moon Umbriel: A Blue Moon Uranus’s moon Umbriel’s dark surface reflects only about half as much light as Ariel which is of a similar size. The surface of the moon has a blue tint while sites of fresh impacts have a much stronger blue colour. The leading hemisphere appears to be redder than the trailing hemisphere. The red colour may be attributed to weathering from a combination of tiny meteorites known as micrometeorites and charged particles from Uranus’s magnetosphere striking the surface. Cratered Satellite As of yet, no canyons, or chasmata, have been discovered on the surface of Uranus’s moon Umbriel. This is chiefly because of the poor quality of the images provided to scientists. The only geological features found so far have been craters. Many of these craters have peaks at their centres. It is thought to have gotten its dark appearance from heavy impacts with comets and asteroids. In fact, the moon is the second most heavily cratered satellite in the Uranian system after Oberon . The largest of its craters measures an impressive 210 kilometres (130 miles) across.

The most prominent of all the craters on Uranus’s moon Umbriel is Wunda crater. Measuring 131 kilometres (81 miles) across its basin it is very bright and creates a highly visible contrast next to the dark surface of the moon. Formation And Future Like the other Uranian moons, Umbriel is believed to have been born out of an accretion disc either left over after the formation of Uranus or after the likely impact that gave Uranus its bizarre tilt. This process is thought to have taken several thousand years to complete. In its past, Uranus’s moon Umbriel may have had a liquid water ocean at the boundary between the icy mantle and the rocky core. However, this liquid ocean, if it had existed, would have long since frozen. Uranus’s moon Umbriel has only been photographed up-close once by a space probe during a fly-by. In 1986, on its way to the far reaches of the Solar System and beyond, Voyager 2 mapped roughly 40 per cent of the surface of Uranus’s moon Umbriel. The Voyager probe is the only spacecraft that has been in close proximity to the moon.

No other missions have been planned to visit the moon in the foreseeable future. Highly Recommended Reading Check out Yellow Magpie’s Uranus: The Coldest Ice Giant for more insight into the largest planet in the Solar System. You may also like to take a gander at The Solar System And Beyond: A Guide To The Cosmos . Cosmos is a highly recommended book. It contains large, full-page pictures of the asteroids and writing on the subject by the highly competent author, Giles Sparrow. Amazon.co.uk For people living in Ireland or the United Kingdom, you can access: Cosmos from here. Amazon.ca For those who live in Canada, you can obtain: Cosmos here. Amazon.de

Question: Umbriel and Ariel are moons of which planet?
Answer: Uranus