Uranus's Moon Oberon - Universe Today Universe Today by Matt Williams In 1610, Galileo’s observed four satellites orbiting the distant gas giant of Jupiter. This discovery would ignite a revolution in astronomy, and encouraged further examinations of the outer Solar System to see what other mysteries it held. In the centuries that followed, astronomers not only discovered that other gas giants had similar systems of moons, but that these systems were rather extensive. For example, Uranus has a system of 27 confirmed satellites. Of these, Oberon is the outermost satellite, as well as the second largest and second most-massive. Named in honor of a mythical king of fairies, it is also the ninth most massive moon in the Solar System. Discovery and Naming: Discovered in 1787 by Sir William Herschel, Oberon was one of two major satellites discovered in a single day (the other being Uranus’ moon of Titania). At the time, he reported observing four other moons; however, the Royal Astronomical Society would later determine that these were spurious. It would be almost five decades after the moons were discovered that an astronomer other than Herschel observed them.

Initially, Oberon was referred to as “the second satellite of Uranus”, and in 1848, was given the designation Uranus II by William Lassell. In 1851, Lassell discovered Uranus’ other two moons – later named Ariel and Miranda – and began numbering them based on their distance from the planet . Oberon was thus given the designation of Uranus IV. Size comparison between the Earth, the Moon, and Uranus’ moon of Oberon. Credit: Tom.Reding/Public Domain By 1852, Herschel’s son John suggested naming the moon’s his father observed Oberon and Titania , at the request of Lassell himself. All of these names were taken from the works of William Shakespeare and Alexander Pope, with the name Oberon being derived from the King of the Fairies in A Midsummer Night’s Dream. Size, Mass and Orbit: With a diameter of approx.

1,523 kilometers, a surface area of 7,285,000 km², and a mass of 3.014 ± 0.075 x 10²¹ kilograms, Oberon is the second largest, and second most massive of Uranus’ moons. It is also the ninth most massive moon in the solar system. At a distance of 584,000 km from Uranus, it is the farthest of the five major moons from Uranus. However, this distance is subject to change, as Oberon has a small orbital eccentricity and inclination relative to Uranus’ equator. It has an orbital period of about 13.5 days, coincident with its rotational period. This means that Oberon is a tidally-locked, synchronous satellite with one face always pointing toward the planet. Since (like all of Uranus’ moons) Oberon orbits the planet around its equatorial plane, and Uranus orbits the Sun almost on its side, the moon experiences a rather extreme seasonal cycle.

Essentially, both the northern and southern poles spend a period of 42 years in complete darkness or complete sunlight – with the sun rising close to the zenith over one of the poles at each solstice. Voyager 2: So far, the only close-up images of Oberon have been provided by the Voyager 2 probe, which photographed the moon during its flyby of Uranus in January 1986. The images cover about 40% of the surface, but only 25% of the surface was imaged with a resolution that allows geological mapping. In addition, the time of the flyby coincided with the southern hemisphere’s summer solstice, when nearly the entire northern hemisphere was in darkness. This prevented the northern hemisphere from being studied in any detail. No other spacecraft has visited the Uranian system before or since, and no missions to the planet are currently being planned. Composition: Oberon’s density is higher than the typical density of Uranus’ satellites, at 1.63 g/cm³. This would indicate that the moon consists of roughly equal proportions of water ice and a dense non-ice component. The latter could be made of rock and carbonaceous material including heavy organic compounds.

Spectroscopic observations have confirmed the presence of crystalline water ice in the surface of the moon. It is believed that Oberon, much like the other Uranian moons, consists of an icy mantle surrounding a rocky core. If this is true, then the radius of the core (480 km) would be equal to approx. 63% of the radius of the moon, and its mass would be around 54% of the moon’s mass. False-color image of Oberon, showing the Hamlet and Othello craters (right of center and lower left) and the Mommur Chasma (upper left). Credit: USGS Astrogeology Research Program Currently, the full composition of the icy mantle is unknown. However, it it were to contain enough ammonia or other antifreeze compounds, the moon may possess a liquid ocean layer at the core–mantle boundary. The thickness of this ocean, if it exists, would be up to 40 km and its temperature would be around 180 K. It is unlikely that at these temperatures, such an ocean could support life. But assuming that hydrothermal vents exist in the interior, it is possible life could exist in small patches near the core.

However, the internal structure of Oberon depends heavily on its thermal history, which is poorly known at present. Interesting Facts: Oberon is the second-darkest large moon of Uranus (after Umbriel), with a surface that appears to be generally red in color – except where fresh impact deposits have left neutral or slightly blue colors. In fact, Oberon is the reddest moon amongst its peers, with a trailing hemisphere that is significantly redder than its leading hemisphere. The reddening of the surfaces is often a result of space weathering caused by bombardment of the surface by charged particles and micrometeorites over many millions of years. However, the color asymmetry of Oberon is more likely caused by accretion of a reddish material spiraling in from outer parts of the Uranian system. Oberon’s surface is the most heavily cratered of all the Uranian moons, which would indicate that Oberon has the most ancient surface among them. Consistent with the planet’s name, these surface features are named after characters in Shakespearean plays.

The largest known crater, Hamlet, measures 206 kilometers in diameter, while the Macbeth, Romeo, and Othello craters measure 203, 159, and 114 km respectively. Uranus and its five major moons. Credit: space.com Other prominent surface features are what is known as chasmata – steep-sided depressions that are comparable to rift valleys or escarpments here on Earth. The largest known chasmata on Oberon is the Mommur Chasma, which measures 537 km in diameter and takes its name from the enchanted forest in French folklore that was ruled by Oberon. As you can plainly see, there is much that remains unknown about this satellite. Much like its peers, how they came to be, and what secrets may lurk beneath their surfaces, is still open to speculation. One can only hope that future generations will choose to mount another Voyager-like expedition to the Outer Solar System for the sake of studying the Uranian satellites. For more information, check out Oberon and the moon Oberon . Astronomy Cast has an episode on Uranus .

Reference: Oberon Oberon Oberon ("OH buh ron") is the outermost of Uranus ' large satellites and the second largest: orbit : 583,420 km from Uranus diameter : 1523 km mass : 3.03e21 kg Oberon is the King of the Fairies and husband of Titania in Shakespeare's Midsummer-Night's Dream. Discovered by Herschel in 1787. Oberon and Umbriel appear quite similar though Oberon is 35% larger. All of Uranus' large moons are a mixture of about 40-50% water ice with the rest rock, a somewhat larger fraction of rock than Saturn 's large moons such as Rhea . Oberon's heavily cratered surface has probably been stable since its formation. It has far more and larger craters than do Ariel and Titania . Some of the craters have rays of ejecta similar to those seen on Callisto . Some of the crater floors are dark, perhaps covered with darker material (dirty water?) that upwelled into the crater. Large faults are also seen across the entire southern hemisphere of Oberon.

This indicates some geologic activity early in Oberon's history. The picture above shows a mountain on the limb that rises 6 km above its surrounds. It is actually possible to see Uranus's 4 largest moons with an amateur telescope. But it takes a very dark sky and a telescope with at least a 12 inch (30 cm) aperture. More about Oberon another APOD Open Issues Why have Oberon and Umbriel apparently been inactive throughout their histories while Ariel and Titania have been at least partially resurfaced? The moon Oberon - History, structure, orbit, surface, evolution The moon Oberon Oberon. © based on NASA images William Herschel. © National Portrait Gallery, London Oberon is the outermost and one among the 27 moons of Uranus. William Herschel discovered it in the year 1787 and it is the second largest as well as the second most massive moon of Uranus. He discovered Oberon and Titania on the same day. In the entire solar system it is the ninth most massive moon.

Much like all the other moons of Uranus, Oberon was also named in 1852 after a character in Shakespeare’s play, A Midsummer Night’s Dream. Though initially named as Uranus II according to the order in which it was discovered, it was later renamed as Uranus IV according to its distance from the planet. Physical structure of Oberon Oberon is assumed to have formed from the diffuse material around Uranus after the planet was formed. The structure of Oberon is that of a rocky core covered by a mantle made of ice. However, the moon consists of equal amounts of rock and ice. It is assumed that a layer of liquid water may be present between the core and the mantle. The surface of Oberon is slightly dark and red in color and is covered by a number of craters that may have been created by the impact of asteroids and comets. Some of the craters are almost 210 km in diameter. The surface of Oberon also has many deep elongated depressions called chasmata. Oberon and Uranus. © NASA These are assumed to have been formed when the interior of the moon was still expanding during early years of its evolution.

It is believed that it is remained stable from the days its formation. The radius of Oberon is about 763 km and has a surface area of 7.2 million km. The density of Oberon is about 1.63 g/cm3 and has a surface gravity of about 0.348 m/s2. The temperature in the moon varies between 70 and 80 degrees Kelvin. Oberon's orbit The Oberon’s orbit is at a distance of 584,000 km from Uranus. The orbital period of the moon is 13.5 days. This coincides with its rotational period. As a result, one face of the moon is tidally locked with Uranus, that is, it always faces the planet. Oberon spends a major part of its orbit outside the magnetosphere of Uranus. This is a reason why its surface is struck by solar wind directly. For those satellites that orbit inside the magnetosphere, the trailing hemispheres of these moons are continuously struck by magnetospheric plasma which leads to darkening of these hemispheres unlike that of Oberon. Uranus orbits the sun almost on its side.

The moons of Uranus orbit the planet on its equatorial plane. This causes the satellites to experience extreme seasonal cycles. The north and south poles of Oberon have 42 years of continuous darkness and the next 42 years of continuous sunlight. During each solstice, the sun rises close to the zenith of one of the poles. During the summer solstice, the northern hemisphere is left totally darkened. Oberon’s internal structure Oberon’s density is indicative of the fact that it contains equal proportions of water ice as well as a non-ice dense component. The non-ice material is believed to be made up of carbonaceous material, organic compounds, and rock. Spectroscopic findings have corroborated the presence of water ice on the surface of Oberon. Internal structure of Oberon. © NASA images Whereas other Uranian moons exhibit more water ice presence in their leading hemispheres, Oberon exhibits stronger signatures in its trailing hemisphere. This discrepancy is seen as the result of formation of soil due to impacts, which is more predominant on its leading hemisphere. Impacts from meteorites generally knock off ice from the surface and leave behind material that is non ice and dark.

This darkening of this material is assumed to have been caused by radiation processing of compounds of an organic nature. The radius of the core of Oberon is about 480 km. The pressure at the center of the core is about 5 kbar. The exact composition of the icy mantle is unclear. In case the mantle contains a sufficient quantity of antifreeze, there is every chance that there is an ocean that exists between the icy mantle and the rocky core. The thickness of the ocean can be up to 40 km and temperature about 180 degrees Kelvin. Oberon’s geology and surface characteristics Oberon is a dark moon of Uranus. The surface of Oberon is red in color and shows tinges of blue where there have been fresh impacts and deposits thereof. Oberon’s geology and surface characteristics. © NASA The leading hemisphere of Oberon is redder than its trailing hemisphere. Meteorites of a very small size and charged particles that bombard the surface are seen to have caused the reddening of the moon’s surface. Another theory has it that the reddening may have been caused by reddish material accretion from the outer sections including irregular satellites that are seen to impact the leading hemisphere more.

Oberon’s surface is seen to be made up of primarily craters and chasmata. Oberon has the most number of craters when compared to the other moons of Uranus. These high numbers are indicative of the fact that the surface of Oberon is the most ancient one when compared with that of the other moons. The largest crater is Hamlet which is about 206 km in diameter. The craters are surrounded by rays of fresh ice. All known craters (Othello, Macbeth, and Hamlet) have floors that are dark due to deposition of material. Some of the basins formed by impacts have large peaks at the center. Voyager imager shows one such peak that is about 11 km in height. Oberon’s surface also has a number of chasmata or canyons that intersect the landscape. The more recent ones are brighter. Mommur Chasma is the most prominent canyon in Oberon. These canyons are cracks on the crust of ice. Tectonic activity for a period after the formation of the moon has been responsible for the formation of ice.

The cracking of the crust is believed to have taken place in two phases giving rise to old and comparatively new canyons. As regards the nature of the dark patches seen at the bottom of the craters, some scientists believe that they are of volcanic origin, whereas others feel that high impacts may have brought out dark material from below the ice. Oberon’s evolution Voyager 2. © NASA Formed form the accretion of dust and debris, the comparatively high density of Oberon indicates that it may have been poor in water content and containing more rocky material. The accretion is assumed to have taken place over many thousand years. The impacts caused the outer layer of the moon to heat up. After the moon was formed, the layer below the surface cooled but the core remained heated due to radioactive decay. The outer layer contracted while the inner core expanded for about 200 million years. These stresses are assumed to have created the canyons. Any such activity caused by the above mentioned happening are believed to have ceased billions of years ago. Pictures of Oberon have been gathered by Voyager 2 probe during its flight past Uranus in January 1986.

The pictures were shot from a distance of 470,600 km. There have been no pictures of the darkened northern hemisphere of the moon during Voyager’s flight. Oberon (moon) | Gravity Wiki | Fandom powered by Wikia Oberon (pronounced /ˈoʊbərɒn/ ), [note 1] also designated Uranus IV, is the outermost major moon of the planet Uranus . It is the second largest and second most massive of Uranian moons, and the ninth most massive moon in the Solar System. Discovered by William Herschel in 1787, Oberon is named after a character in Shakespeare's A Midsummer Night's Dream . Its orbit lies partially outside Uranus's magnetosphere . Oberon consists of approximately equal amounts of ice and rock , and is likely differentiated into a rocky core and an icy mantle . A layer of liquid water may be present at the core/mantle boundary. The surface of Oberon, which is dark and slightly red in color, appears to have been primarily shaped by asteroid and comet impacts. It is covered by numerous impact craters reaching 210 km in diameter.

Oberon possesses a system of canyons ( scarps ) formed as a result of the expansion of its interior during its early evolution. This moon probably formed from the accretion disk that surrounded Uranus just after the planet's formation. As of 2008, the Uranian system has been studied up close only once: by the spacecraft Voyager 2 in January 1986. It took several images of Oberon, which allowed mapping of about 40% of the moon’s surface. Contents Edit Oberon was discovered by William Herschel on January 11, 1787; on the same day he discovered Uranus's largest moon, Titania . [1] [2] He later reported the discoveries of four more satellites, [3] although they were subsequently revealed as spurious. [4] For nearly fifty years following their discovery, Titania and Oberon would not be observed by any instrument other than William Herschel's, [5] although the moon can be seen from Earth with a present-day high end amateur telescope. [6] All of the moons of Uranus are named after characters created by William Shakespeare or Alexander Pope .

The name Oberon was derived from Oberon , the King of the Fairies in A Midsummer Night's Dream . [7] The names of all four satellites of Uranus then known were suggested by Herschel's son John in 1852, at the request of William Lassell , [8] who had discovered the other two moons, Ariel and Umbriel , the year before. [9] The adjectival form of the name is Oberonian, pronounced /ˌɒbəˈroʊniən/ . [10] Oberon was initially referred to as "the second satellite of Uranus", and in 1848 was given the designation Uranus II by William Lassell, [11] although he sometimes used William Herschel's numbering (where Titania and Oberon are II and IV). [12] In 1851 Lassell eventually numbered all four known satellites in order of their distance from the planet by Roman numerals , and since then Oberon has been designated Uranus IV.

[13] Orbit Edit Oberon orbits Uranus at the distance of about 584,000 km, being the farthest from the planet among its five major moons. [note 2] Oberon's orbit has a small orbital eccentricity and inclination (relative to the equator of Uranus). [14] Its orbital period is around 13.5 days, coincident with its rotational period . In other words, Oberon is a synchronous satellite , tidally locked , with one face always pointing toward the planet. [15] Oberon spends a significant part of its orbit outside the Uranian magnetosphere . [16] As a result, its surface is directly struck by the solar wind . [17] This is important, because the trailing hemispheres of satellites orbiting inside a magnetosphere are struck by the magnetospheric plasma, which co–rotates with the planet. [16] This bombardment may lead to the darkening of the trailing hemispheres, which is actually observed for all Uranian moons except Oberon (see below).

[17] Because Uranus orbits the Sun almost on its side, and its moons orbit in the planet's equatorial plane, they (including Oberon) are subject to an extreme seasonal cycle. Both northern and southern hemispheres spend 42 years in a complete darkness, and another 42 years in continuous sunlight. [17] Once every 42 years, when Uranus has an equinox and its equatorial plane intersects the Earth, mutual occultations of Uranus's moons become possible. One such event, which lasted for about six minutes, was observed on May 4, 2007, when Oberon occulted Umbriel. [18] Composition and internal structure Edit Oberon is the largest and most massive of Uranian moons after Titania , and the ninth most massive moon in the Solar System. [note 3] Oberon's density of 1.63 g/cm3, [20] which is higher than the typical density of Saturn's satellites, indicates that it consists of roughly equal proportions of water ice and a dense non-ice component. [21] The latter could be made of rock and carbonaceous material including heavy organic compounds .

[15] The presence of water ice is supported by spectroscopic observations, which have revealed crystalline water ice on the surface of the moon. [17] Water ice absorption bands are stronger on Oberon's trailing hemisphere than on the leading hemisphere. This is the opposite of what is observed on other Uranian moons, where the leading hemisphere exhibits stronger water ice signatures. [17] The cause of this asymmetry is not known, but it may be related to impact gardening (the creation of soil via impacts) of the surface, which is stronger on the leading hemisphere. [17] Meteorite impacts tend to sputter (knock out) ice from the surface, leaving dark non-ice material behind. [17] The dark material itself may have formed as a result of radiation processing of methane clathrates or radiation darkening of other organic compounds. [15] [22] Oberon may be differentiated into a rocky core surrounded by an icy mantle .

[21] If this is the case, the radius of the core (480 km) is about 63% of the radius of the moon, and its mass is around 54% of the moon’s mass—the parameters are dictated by moon's composition. The pressure in the center of Oberon is about 0.5 GPa (5 kbar ). [21] The current state of the icy mantle is unclear. If the ice contains enough ammonia or other antifreeze , Oberon may possess a liquid ocean layer at the core-mantle boundary. The thickness of this ocean, if it exists, is up to 40 km and its temperature is around 180 K. [21] However the internal structure of Oberon depends heavily on its thermal history, which is poorly known at present. Surface features and geology File:Oberon USGS.jpg Oberon is the second-darkest large moon of Uranus after Umbriel . [23] Its surface shows a strong opposition surge : its reflectivity decreases from 31% at a phase angle of 0° ( geometrical albedo ) to 22% at an angle of about 1°.

Oberon has a very low bond albedo of about 14%. [23] Its surface is generally slightly red in color, except for fresh impact deposits, which are neutral or slightly blue. [24] The trailing and leading hemispheres are asymmetrical: the former is less red than the latter, because it contains less dark red material. [22] The reddening of the surfaces is usually a result of space weathering caused by bombardment of the surface by charged particles and micrometeorites over the age of the Solar System . [22] 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. [25] Scientists have recognized two classes of geological feature on Oberon: craters and chasmata (canyons). [15] The ancient surface of Oberon is the most heavily cratered of all the Uranian moons, with a crater density approaching saturation—when the formation of new craters is balanced by destruction of old ones.

[note 4] [26] The crater diameters range from a few kilometers at the low end to 206 kilometers for the largest known crater, [26] Hamlet . [27] Many large craters are surrounded by bright impact ejecta ( rays ) consisting of relatively fresh ice. [15] The largest craters, Hamlet, Othello and Macbeth, have floors made of a very dark material deposited after their formation. [26] A peak with a height of about 11 km was observed in some Voyager images near the south-eastern limb of Oberon, [28] which may be the central peak of a large impact basin with a diameter of about 375 km. [28] Oberon's surface is intersected by a system of canyons , which, however, are less widespread than those found on Titania. [15] The canyons are probably normal faults or scarps , [note 5] which can be either old or fresh: the latter transect the bright deposits of some large craters, indicating that they formed later. [29] The most prominent among Oberonian canyons is Mommur Chasma .

[30] The geology of Oberon was influenced by two competing forces: impact crater formation and endogenic resurfacing. [29] The former acted over the moon's entire history and is primarily responsible for its present-day appearance. [26] The latter processes were active for a period following the moon's formation. The endogenic processes were mainly tectonic in nature and led to the formation of the canyons, which are actually giant cracks in the ice crust. [29] The canyons obliterated parts of the older surface. [29] The cracking of the crust was caused by the expansion of Oberon by about 0.5%, [29] which occurred in two phases corresponding to the old and young canyons. The nature of the dark patches, which mainly occur on the leading hemisphere and inside craters, is not known. Some scientists hypothesized that they are of cryovolcanic origin (analogs of Lunar maria ), [26] while others think that the impacts excavated dark material buried beneath the pure ice ( crust ).

[24] In the latter case Oberon should be at least partially differentiated, with the ice crust lying atop of the non-differentiated interior. [24] Named surface features on Oberon [31] (Surface features on Oberon are named for characters from Shakespeare's works) [32] Feature Edit Oberon 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 . [33] The precise composition of the subnebula is not known; however, the relatively high density of Oberon and other Uranian moons compared to the moons of Saturn indicates that it may have been relatively water-poor. [note 6] [15] Significant amounts of nitrogen and carbon may have been present in the form of carbon monoxide and N2 instead of ammonia and methane. [33] 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.

[15] Oberon's accretion probably lasted for several thousand years. [33] The impacts that accompanied accretion caused heating of the moon's outer layer. [34] The maximum temperature of around 230 K was reached at the depth of about 60 km. [34] After the end of formation, the subsurface layer cooled, while the interior of Oberon heated due to decay of radioactive elements present in its rocks. [15] The cooling near-surface layer contracted, while the interior expanded. This caused strong extensional stresses in the moon's crust leading to cracking. The present-day system of canyons may be a result of this process, which lasted for about 200 million years, [35] implying that any endogenous activity ceased billions of years ago. [15] The initial accretional heating together with continued decay of radioactive elements were probably strong enough to melt the ice [35] if some antifreeze like ammonia (in the form of ammonia hydrate ) or some salt was present. [21] Further melting may have led to the separation of ice from rocks and formation of a rocky core surrounded by an icy mantle.

A layer of liquid water (ocean) rich in dissolved ammonia may have formed at the core–mantle boundary. [21] The eutectic temperature of this mixture is 176 K. [21] If the temperature dropped below this value the ocean would have frozen by now. The freezing of the water led to the expansion of the interior, which may have also been responsible for the formation of canyons. [26] Still, the present knowledge of the evolution of Oberon is very limited. Exploration Edit Template:Mainarticle So far the only close-up images of Oberon 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 Oberon was only 470,600 km, [36] the best images of this moon have spatial resolution of about 6 km. [26] The images cover about 40% of the surface, but only images for 25% of the surface have quality, which allows the geological mapping .

At the time of the flyby the southern hemisphere of Oberon was pointed towards the Sun , so the northern (dark) hemisphere could not be studied. [15] No other spacecraft ever visited Uranus (and Oberon), and no mission to this planet is planned in the foreseeable future.

See also ↑ 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 Lassell5 ↑ 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 Shakespeare ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Lassell2 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Lassell3 ↑ 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 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 Ness1986 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Grundy2006 ↑ Cite error:

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 ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Croft1989 ↑ " Oberon: Mommur ".

Gazetteer of Planetary Nomenclature. USGS Astrogeology. Retrieved on 2009-03-06. ↑ 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 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 Uranus's Moon Oberon: A Cold Unknown World Uranus’s Moon Oberon: A Cold Unknown World [adsense] Uranus’s Moon Oberon It is a world that remains only partly seen. A flying-probe took a few images as it shoots past the far-away satellite.

From these paltry pictures we have garnered much of our present picture of the Uranus’s moon Oberon. Uranus’s moon Oberon is the second largest moon of Uranus. Like many of the other satellites orbiting Uranus, Oberon is named after characters from Shakespeare’s A Midsummer Night’s Dream. Uranus’s moon Oberon orbits Uranus at a distance of 584,000 kilometres (362,000 miles) taking roughly 13.5 days to complete one trip around the planet. The moon is a very cold world with temperatures as low as minus 203 degrees Celsius (minus 333 degrees Fahrenheit) Uranus’s Moon Oberon: Violent Origins It is thought that the moon was created from an accretion disk that was left over after Uranus’s formation. This field of debris coalesced over thousands of years and formed the satellite. Like the other Uranian moons, Uranus’s Oberon is composed mainly of nearly equal amounts of ice and solid rock. Scientists believe that the moon has an icy mantle and an inner rocky core.

There is considerable speculation as to whether or not there is a layer of liquid water present at the boundary between the core and the mantle. Heavily Cratered Canyon Surface From the 25 per cent that Voyager 2 mapped in sufficient detail scientists have noted two types of features on Uranus’s moon Oberon’s surface. These are canyons called chasmata and craters. Oberon’s surface is thought to be the most heavily cratered of all the Uranian satellites. In fact, it is almost saturated with craters which means that a new impact is likely to erase older impacts. The largest canyon so far discovered on Uranus’s moon Oberon is Momur Chasma. Oberon’s canyons were created quite early in its history and are the result of tectonic activity when the moon expanded. Uranus’s moon Oberon’s surface is pockmarked with scars from heavy impacts from both comets and asteroids.Unfortunately, only 40 per cent of the entire moon’s surface has been mapped. This was done by Voyager 2 in 1986 as the probe navigated its way past the planets on its long trip out of the Solar System.

However, just 25 per cent of the surface was mapped in sufficient detail as to allow geological mapping. The entire northern hemisphere was shrouded in darkness during Voyager 2’s mapping so its features are completely unknown. One of the largest craters so far discovered on the moon’s surface is 210 kilometres (130 miles) across. Uranus’s Moon Oberon: A Hostile Orbit Uranus odd orbital tilt means that the Uranian moons are subject to extreme seasons. Each of the hemispheres of Uranus’s moon Oberon experience complete darkness and complete sunlight for 42 years at a time. The moon is tidally locked, like our own Moon . This means that one side continuously faces Uranus while the other always points away from the planet’s surface. Like Titania , a substantial portion of the orbit of Uranus’s moon Oberon’s resides outside the magnetosphere of Uranus. This means that Oberon is bombarded by magnetospheric plasma. Nevertheless, the darkening of the trailing hemisphere, which is typical of the Uranian moon system, is not found on Oberon. Scientists know this because of the density of the moon.

One theory proposed for this departure from the other satellites is that the trailing hemisphere of Uranus’s moon Oberon has more water ice compared to its leading hemisphere. This is completely at odds with all the other Uranian satellites. One theory proposed to explain this anomaly is impact gardening. Impact gardening is the creation of fine soil through heavy impacts. A Liquid Ocean? Uranus’s moon Oberon may have a liquid ocean at the core-mantle boundary. This is heavily reliant on there being enough of an anti-freeze material present to stop the water freezing. If the ocean does exist it could be up to 40 kilometres (25 miles) deep. At this stage, given the dearth of information, it is impossible to say whether this is the case or not. It may be quite some time before a spacecraft is sent to explore either Uranus or Oberon. As of now there are no planned missions to Uranus’s moon Oberon. 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 wish 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 Uranus’s Moon of Oberon - Technology Org Technology Org Uranus’s Moon of Oberon Posted June 22, 2015 In 1610, Galileo’s observed four satellites orbiting the distant gas giant of Jupiter. This discovery would ignite a revolution in astronomy, and encouraged further examinations of the outer Solar System to see what other mysteries it held. In the centuries that followed, astronomers not only discovered that other gas giants had similar systems of moons, but that these systems were rather extensive. Oberon, as imaged by the Voyager 2 probe during its flyby on Jan. 24, 1986. Credit: NASA For example, Uranus has a system of 27 confirmed satellites. Of these, Oberon is the outermost satellite, as well as the second largest and second most-massive.

Named in honor of a mythical king of fairies, it is also the ninth most massive moon in the Solar System. Discovery and Naming: Discovered in 1787 by Sir William Herschel, Oberon was one of two major satellites discovered in a single day (the other being Uranus’ moon of Titania). At the time, he reported observing four other moons; however, the Royal Astronomical Society would later determine that these were spurious. It would be almost five decades after the moons were discovered that an astronomer other than Herschel observed them. Initially, Oberon was referred to as “the second satellite of Uranus”, and in 1848, was given the designation Uranus II by William Lassell. In 1851, Lassell discovered Uranus’ other two moons – later named Ariel and Miranda – and began numbering them based on their distance from the planet . Oberon was thus given the designation of Uranus IV. Size comparison between the Earth, the Moon, and Uranus’ moon of Oberon.

Credit: Tom.Reding/Public Domain By 1852, Herschel’s son John suggested naming the moon’s his father observed Oberon and Titania , at the request of Lassell himself. All of these names were taken from the works of William Shakespeare and Alexander Pope, with the name Oberon being derived from the King of the Fairies in A Midsummer Night’s Dream. Size, Mass and Orbit: With a diameter of approx. 1,523 kilometers, a surface area of 7,285,000 km², and a mass of 3.014 ± 0.075 x 10²¹ kilograms, Oberon is the second largest, and second most massive of Uranus’ moons. It is also the ninth most massive moon in the solar system. At a distance of 584,000 km from Uranus, it is the farthest of the five major moons from Uranus. However, this distance is subject to change, as Oberon has a small orbital eccentricity and inclination relative to Uranus’ equator. It has an orbital period of about 13.5 days, coincident with its rotational period.

This means that Oberon is a tidally-locked, synchronous satellite with one face always pointing toward the planet. Since (like all of Uranus’ moons) Oberon orbits the planet around its equatorial plane, and Uranus orbits the Sun almost on its side, the moon experiences a rather extreme seasonal cycle. Essentially, both the northern and southern poles spend a period of 42 years in complete darkness or complete sunlight – with the sun rising close to the zenith over one of the poles at each solstice. Voyager 2: So far, the only close-up images of Oberon have been provided by the Voyager 2 probe, which photographed the moon during its flyby of Uranus in January 1986. The images cover about 40% of the surface, but only 25% of the surface was imaged with a resolution that allows geological mapping. In addition, the time of the flyby coincided with the southern hemisphere’s summer solstice, when nearly the entire northern hemisphere was in darkness. This prevented the northern hemisphere from being studied in any detail. No other spacecraft has visited the Uranian system before or since, and no missions to the planet are currently being planned.

Composition: Oberon’s density is higher than the typical density of Uranus’ satellites, at 1.63 g/cm³. This would indicate that the moon consists of roughly equal proportions of water ice and a dense non-ice component. The latter could be made of rock and carbonaceous material including heavy organic compounds. Spectroscopic observations have confirmed the presence of crystalline water ice in the surface of the moon. It is believed that Oberon, much like the other Uranian moons, consists of an icy mantle surrounding a rocky core. If this is true, then the radius of the core (480 km) would be equal to approx. 63% of the radius of the moon, and its mass would be around 54% of the moon’s mass. False-color image of Oberon, showing the Hamlet and Othello craters (right of center and lower left) and the Mommur Chasma (upper left). Credit: USGS Astrogeology Research Program Currently, the full composition of the icy mantle is unknown. However, it it were to contain enough ammonia or other antifreeze compounds, the moon may possess a liquid ocean layer at the core–mantle boundary.

The thickness of this ocean, if it exists, would be up to 40 km and its temperature would be around 180 K. This, in short, would mean that Oberon could house a warm water ocean that would theoretically be capable of supporting life. However, the internal structure of Oberon depends heavily on its thermal history, which is poorly known at present. Interesting Facts: Oberon is the second-darkest large moon of Uranus (after Umbriel), with a surface that appears to be generally red in color – except where fresh impact deposits have left neutral or slightly blue colors. In fact, Oberon is the reddest moon amongst its peers, with a trailing hemisphere that is significantly redder than its leading hemisphere. The reddening of the surfaces is often a result of space weathering caused by bombardment of the surface by charged particles and micrometeorites over many millions of years. However, the color asymmetry of Oberon is more likely caused by accretion of a reddish material spiraling in from outer parts of the Uranian system. Oberon’s surface is the most heavily cratered of all the Uranian moons, which would indicate that Oberon has the most ancient surface among them.

Consistent with the planet’s name, these surface features are named after characters in Shakespearean plays. The largest known crater, Hamlet, measures 206 kilometers in diameter, while the Macbeth, Romeo, and Othello craters measure 203, 159, and 114 km respectively. Uranus and its five major moons. Credit: space.com Other prominent surface features are what is known as chasmata – steep-sided depressions that are comparable to rift valleys or escarpments here on Earth. The largest known chasmata on Oberon is the Mommur Chasma, which measures 537 km in diameter and takes its name from the enchanted forest in French folklore that was ruled by Oberon. As you can plainly see, there is much that remains unknown about this satellite. Much like its peers, how they came to be, and what secrets may lurk beneath their surfaces, is still open to speculation. One can only hope that future generations will choose to mount another Voyager-like expedition to the Outer Solar System for the sake of studying the Uranian satellites. For more information, check out Oberon and the moon Oberon .

Source: Universe Today , written by Matt Williams Related Topics: Oberon, moon of Uranus - The Solar System on Sea and Sky Voyager 2 close-up of Oberon (NASA/NSSDC) King of the Fairies Oberon [OH buh ron] is the outermost of Uranus' moons and is the second largest. It was named after the King of the Fairies and husband of Titania in Shakespeare's Midsummer-Night's Dream. Oberon was discovered in 1787 by the British astronomer, Sir William Herschel, who also discovered Uranus. Most of what we now know about this moon was discovered by Voyager 2 in 1986. Mysterious Dark Craters Oberon is very similar to Umbriel in composition, although Oberon is about 35% larger. As with all of Uranus' moons, it is believed to be composed of about half water ice and half rocky material. The surface of Oberon is heavily cratered. The lack of other surface features indicates that it has probably been stable since its formation. An unidentified substance covers the floors of many of Oberon's craters. Astronomers are not yet sure where this substance originates.

One theory suggests that it could be "dirty water" that upwelled into the crater after impact. Features of Oberon The most notable features of Oberon are its craters. These craters are more numerous and much larger than those on Ariel and Titania. Some of these craters exhibit bright rays of ejecta material similar to those on Jupiter's moon, Callisto. Several images of Oberon show a lone mountain peak rising 4 miles (6 km) above the surface. In the southern hemisphere, large faults can be seen crossing the surface. This may be evidence of some type of geologic activity early in the moon's history. Oberon has no detectable atmosphere and no magnetic field. Oberon | astronomy | Britannica.com astronomy Enceladus Oberon, outermost of the five major moons of Uranus and the second largest of the group. Oberon was discovered in 1787 by the English astronomer William Herschel , who had found Uranus in 1781; it was named by William’s son, John Herschel , for a character in William Shakespeare’s play A Midsummer Night’s Dream.

Oberon, outermost of the five major moons of Uranus, as recorded by Voyager 2 on Jan. 24, 1986. The … NASA/Caltech/JPL The mean distance of Oberon from the centre of Uranus is about 582,600 km (362,000 miles), and its orbital period is 13.46 days. Like all of Uranus’s large moons, Oberon rotates synchronously with its orbital period, keeping the same hemisphere toward the planet and the same hemisphere forward in its orbit. The moon has a diameter of 1,522 km (946 miles) and a density of 1.63 grams per cubic cm. Like its three large siblings Ariel , Umbriel , and Titania , Oberon is thought to consist of about half water ice , with the remainder made of rocky material and perhaps a small proportion of other frozen volatile materials. Photographic images transmitted by the U.S. Voyager 2 spacecraft when it flew past the Uranian system in 1986 revealed that Oberon’s surface is old and heavily cratered like the highlands of Earth’s Moon .

A few of the numerous bright craters appear to have been flooded by some kind of dark material that upwelled from the moon’s interior.

Question: Oberon is a moon of which planet?
Answer: Uranus