Rings of Jupiter
The rings of Jupiter are a system of faint planetary rings. The Jovian rings were the third ring system to be discovered in the Solar System, after those of Saturn and Uranus. The main ring was discovered in 1979 by the Voyager 1 space probe<ref name=Smith1979/> and the system was more thoroughly investigated in the 1990s by the Galileo orbiter.<ref name=Ockert-Bell1999/> The main ring has also been observed by the Hubble Space Telescope and from Earth for several years.<ref name=Meier1999/> Ground-based observation of the rings requires the largest available telescopes.<ref name=dePater1999/>
The Jovian ring system is faint and consists mainly of dust.<ref name=Smith1979/><ref name=Burns1987/> It has four main components: a thick inner torus of particles known as the "halo ring"; a relatively bright, exceptionally thin "main ring"; and two wide, thick and faint outer "gossamer rings", named for the moons of whose material they are composed: Amalthea and Thebe.<ref name=Esposito2002/>
The main and halo rings consist of dust ejected from the moons Metis, Adrastea and perhaps smaller, unobserved bodies as the result of high-velocity impacts.<ref name=Ockert-Bell1999/> High-resolution images obtained in February and March 2007 by the New Horizons spacecraft revealed a rich fine structure in the main ring.<ref name=Morring2007/>
In visible and near-infrared light, the rings have a reddish color, except the halo ring, which is neutral or blue in color.<ref name=Meier1999/> The size of the dust in the rings varies, but the cross-sectional area is greatest for nonspherical particles of radius about 15 μm in all rings except the halo.<ref name=Throop2004/> The halo ring is probably dominated by submicrometre dust. The total mass of the ring system (including unresolved parent bodies) is poorly constrained, but is probably in the range of 1011 to 1016 kg.<ref name=Burns2004/> The age of the ring system is also not known, but it is possible that it has existed since the formation of Jupiter.<ref name=Burns2004/>
A ring or ring arc appears to exist close to the moon Himalia's orbit. One explanation is that a small moon recently crashed into Himalia and the force of the impact ejected the material that forms the ring.
Discovery and structureEdit
Jupiter's ring system was the third to be discovered in the Solar System, after those of Saturn and Uranus. It was first observed on 4 March 1979 by the Voyager 1 space probe.<ref name=Smith1979>Template:Cite journal</ref><ref>Template:Cite book</ref> It is composed of four main components: a thick inner torus of particles known as the "halo ring"; a relatively bright, exceptionally thin "main ring"; and two wide, thick and faint outer "gossamer rings", named after the moons of whose material they are composed: Amalthea and Thebe.<ref name=Esposito2002>Template:Cite journal</ref> The principal attributes of the known Jovian Rings are listed in the table.<ref name=Ockert-Bell1999/><ref name=Burns1987>Template:Cite journal</ref><ref name=Esposito2002/><ref name=Throop2004/>
In 2022, dynamical simulations suggested that the relative meagreness of Jupiter's ring system, compared to that of the smaller Saturn, is due to destabilising resonances created by the Galilean satellites.<ref>Template:Cite journal</ref>
| Name | Radius (km) | Width (km) | Thickness (km) | Optical depthTemplate:Refn (in τ) | Dust fraction | Mass, kg | Notes |
|---|---|---|---|---|---|---|---|
| Halo ring | Template:Val–Template:Val | Template:Val | Template:Val | ~1Template:E-sp | 100% | — | |
| Main ring | Template:Val–Template:Val | Template:Val | 30–300 | 5.9Template:E-sp | ~25% | 107– 109 (dust) 1011– 1016 (large particles) |
Bounded by Adrastea |
| Amalthea gossamer ring | Template:Val–Template:Val | Template:Val | Template:Val | ~1Template:E-sp | 100% | 107– 109 | Connected with Amalthea |
| Thebe gossamer ring | Template:Val–Template:Val | Template:Val | Template:Val | ~3Template:E-sp | 100% | 107– 109 | Connected with Thebe. There is an extension beyond the orbit of Thebe. |
Main ringEdit
Appearance and structureEdit
The narrow and relatively thin main ring is the brightest part of Jupiter's ring system. Its outer edge is located at a radius of about Template:Val (Template:Jupiter radius;Template:Jupiter radius = equatorial radius of Jupiter or Template:Val) and coincides with the orbit of Jupiter's smallest inner satellite, Adrastea.<ref name=Ockert-Bell1999/><ref name=Burns1987/> Its inner edge is not marked by any satellite and is located at about Template:Val (Template:Jupiter radius).<ref name=Ockert-Bell1999>Template:Cite journal</ref>
Thus the width of the main ring is around Template:Val. The appearance of the main ring depends on the viewing geometry.<ref name=Burns2004/> In forward-scattered light<ref group=lower-alpha>The forward-scattered light is the light scattered at a small angle relative to solar light.</ref> the brightness of the main ring begins to decrease steeply at Template:Val (just inward of the Adrastean orbit) and reaches the background level at Template:Val—just outward of the Adrastean orbit.<ref name=Ockert-Bell1999/> Therefore, Adrastea at Template:Val clearly shepherds the ring.<ref name=Ockert-Bell1999/><ref name=Burns1987/> The brightness continues to increase in the direction of Jupiter and has a maximum near the ring's center at Template:Val, although there is a pronounced gap (notch) near the Metidian orbit at Template:Val.<ref name=Ockert-Bell1999/> The inner boundary of the main ring, in contrast, appears to fade off slowly from Template:Val to Template:Val, merging into the halo ring.<ref name=Ockert-Bell1999/><ref name=Burns1987/> In forward-scattered light all Jovian rings are especially bright.
In back-scattered light<ref group=lower-alpha>The back-scattered light is the light scattered at an angle close to 180° relative to solar light.</ref> the situation is different. The outer boundary of the main ring, located at Template:Val, or slightly beyond the orbit of Adrastea, is very steep.<ref name=Burns2004/> The orbit of the moon is marked by a gap in the ring so there is a thin ringlet just outside its orbit. There is another ringlet just inside Adrastean orbit followed by a gap of unknown origin located at about Template:Val.<ref name=Burns2004/> The third ringlet is found inward of the central gap, outside the orbit of Metis. The ring's brightness drops sharply just outward of the Metidian orbit, forming the Metis notch.<ref name=Burns2004>Template:Cite encyclopedia</ref> Inward of the orbit of Metis, the brightness of the ring rises much less than in forward-scattered light.<ref name=dePater1999/> So in the back-scattered geometry the main ring appears to consist of two different parts: a narrow outer part extending from Template:Val to Template:Val, which itself includes three narrow ringlets separated by notches, and a fainter inner part from Template:Val to Template:Val, which lacks any visible structure like in the forward-scattering geometry.<ref name=Burns2004/><ref name=Showalter2005>Template:Cite conference</ref> The Metis notch serves as their boundary. The fine structure of the main ring was discovered in data from the Galileo orbiter and is clearly visible in back-scattered images obtained from New Horizons in February–March 2007.<ref name=Morring2007>Template:Cite journal</ref><ref name="New Horizons">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The early observations by Hubble Space Telescope (HST),<ref name=Meier1999/> Keck<ref name=dePater1999/> and the Cassini spacecraft failed to detect it, probably due to insufficient spatial resolution.<ref name=Throop2004/> However the fine structure was observed by the Keck telescope using adaptive optics in 2002–2003.<ref name=dePater2008>Template:Cite journal</ref>
Observed in back-scattered light the main ring appears to be razor thin, extending in the vertical direction no more than 30 km.<ref name=Burns1987/> In the side scatter geometry the ring thickness is 80–160 km, increasing somewhat in the direction of Jupiter.<ref name=Ockert-Bell1999/><ref name=Throop2004/> The ring appears to be much thicker in the forward-scattered light—about 300 km.<ref name=Ockert-Bell1999/> One of the discoveries of the Galileo orbiter was the bloom of the main ring—a faint, relatively thick (about 600 km) cloud of material which surrounds its inner part.<ref name=Ockert-Bell1999/> The bloom grows in thickness towards the inner boundary of the main ring, where it transitions into the halo.<ref name=Ockert-Bell1999/>
Detailed analysis of the Galileo images revealed longitudinal variations of the main ring's brightness unconnected with the viewing geometry. The Galileo images also showed some patchiness in the ring on the scales 500–1000 km.<ref name=Ockert-Bell1999/><ref name=Burns2004/>
In February–March 2007 New Horizons spacecraft conducted a deep search for new small moons inside the main ring.<ref name=Showalter2007/> While no satellites larger than 0.5 km were found, the cameras of the spacecraft detected seven small clumps of ring particles. They orbit just inside the orbit of Adrastea inside a dense ringlet.<ref name=Showalter2007/> The conclusion, that they are clumps and not small moons, is based on their azimuthally extended appearance. They subtend 0.1–0.3° along the ring, which correspond to Template:Val–Template:Val.<ref name=Showalter2007/> The clumps are divided into two groups of five and two members, respectively. The nature of the clumps is not clear, but their orbits are close to 115:116 and 114:115 resonances with Metis.<ref name=Showalter2007/> They may be wavelike structures excited by this interaction.
Spectra and particle size distributionEdit
Spectra of the main ring obtained by the HST,<ref name=Meier1999/> Keck,<ref name=Wong2006>Template:Cite journal</ref> Galileo<ref name=McMuldroch2000>Template:Cite journal</ref> and Cassini<ref name=Throop2004/> have shown that particles forming it are red, i.e. their albedo is higher at longer wavelengths. The existing spectra span the range 0.5–2.5 μm.<ref name=Throop2004/> No spectral features have been found so far which can be attributed to particular chemical compounds, although the Cassini observations yielded evidence for absorption bands near 0.8 μm and 2.2 μm.<ref name=Throop2004/> The spectra of the main ring are very similar to Adrastea<ref name=Meier1999>Template:Cite journal</ref> and Amalthea.<ref name=Wong2006/>
The properties of the main ring can be explained by the hypothesis that it contains significant amounts of dust with 0.1–10 μm particle sizes. This explains the stronger forward-scattering of light as compared to back-scattering.<ref name=Burns2004/><ref name=Showalter2005/> However, larger bodies are required to explain the strong back-scattering and fine structure in the bright outer part of the main ring.<ref name=Burns2004/><ref name=Showalter2005/>
Analysis of available phase and spectral data leads to a conclusion that the size distribution of small particles in the main ring obeys a power law<ref name=Throop2004/><ref name=Brooks2004>Template:Cite journal</ref><ref name=Burns2001>Template:Cite encyclopedia</ref>
- <math>n(r)=A\times r^{-q}</math>
where n(r) dr is a number of particles with radii between r and r + dr and <math>A</math> is a normalizing parameter chosen to match the known total light flux from the ring. The parameter q is 2.0 ± 0.2 for particles with r < 15 ± 0.3 μm and q = 5 ± 1 for those with r > 15 ± 0.3 μm.<ref name=Throop2004/> The distribution of large bodies in the mm–km size range is undetermined presently.<ref name=Burns2004/> The light scattering in this model is dominated by particles with r around 15 μm.<ref name=Throop2004>Template:Cite journal</ref><ref name=McMuldroch2000/>
The power law mentioned above allows estimation of the optical depth<ref group=lower-alpha name=footnoteC /> <math>\scriptstyle\tau</math> of the main ring: <math>\scriptstyle\tau_l\,=\,4.7\times 10^{-6}</math> for the large bodies and <math>\scriptstyle \tau_s = 1.3\times 10^{-6}</math> for the dust.<ref name=Throop2004/> This optical depth means that the total cross section of all particles inside the ring is about 5000 km².Template:Refn<ref name=Burns2004/> The particles in the main ring are expected to have aspherical shapes.<ref name=Throop2004/> The total mass of the dust is estimated to be 107−109 kg.<ref name=Burns2004/> The mass of large bodies, excluding Metis and Adrastea, is 1011−1016 kg. It depends on their maximum size— the upper value corresponds to about 1 km maximum diameter.<ref name=Burns2004/> These masses can be compared with masses of Adrastea, which is about 2Template:E-sp kg,<ref name=Burns2004/> Amalthea, about 2Template:E-sp kg,<ref name=Anderson2005>Template:Cite journal</ref> and Earth's Moon, 7.4Template:E-sp kg.
The presence of two populations of particles in the main ring explains why its appearance depends on the viewing geometry.<ref name=Burns2001/> The dust scatters light preferably in the forward direction and forms a relatively thick homogenous ring bounded by the orbit of Adrastea.<ref name=Burns2004/> In contrast, large particles, which scatter in the back direction, are confined in a number of ringlets between the Metidian and Adrastean orbits.<ref name=Burns2004/><ref name=Showalter2005/>
Origin and ageEdit
The dust is constantly being removed from the main ring by a combination of Poynting–Robertson drag and electromagnetic forces from the Jovian magnetosphere.<ref name=Burns2001/><ref name=Burns1999>Template:Cite journal</ref> Volatile materials such as ices, for example, evaporate quickly. The lifetime of dust particles in the ring is from 100 to Template:Val,<ref name=Burns2004/><ref name=Burns1999/> so the dust must be continuously replenished in the collisions between large bodies with sizes from 1 cm to 0.5 km<ref name=Showalter2007>Template:Cite journal</ref> and between the same large bodies and high velocity particles coming from outside the Jovian system.<ref name=Burns2004/><ref name=Burns1999/> This parent body population is confined to the narrow—about Template:Val—and bright outer part of the main ring, and includes Metis and Adrastea.<ref name=Burns2004/><ref name=Showalter2005/> The largest parent bodies must be less than 0.5 km in size. The upper limit on their size was obtained by New Horizons spacecraft.<ref name=Showalter2007/> The previous upper limit, obtained from HST<ref name=Meier1999/><ref name=Showalter2005/> and Cassini<ref name=Throop2004/> observations, was near 4 km.<ref name=Burns2004/> The dust produced in collisions retains approximately the same orbital elements as the parent bodies and slowly spirals in the direction of Jupiter forming the faint (in back-scattered light) innermost part of the main ring and halo ring.<ref name=Burns2004/><ref name=Burns1999/> The age of the main ring is currently unknown, but it may be the last remnant of a past population of small bodies near Jupiter.<ref name=Esposito2002/>
Vertical corrugationsEdit
Images from the Galileo and New Horizons space probes show the presence of two sets of spiraling vertical corrugations in the main ring. These waves became more tightly wound over time at the rate expected for differential nodal regression in Jupiter's gravity field. Extrapolating backwards, the more prominent of the two sets of waves appears to have been excited in 1995, around the time of the impact of Comet Shoemaker-Levy 9 with Jupiter, while the smaller set appears to date to the first half of 1990.<ref name = "forensic"> {{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name = "Jupiter's Ring"> {{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name = "Showalter"> Template:Cite journal</ref> Galileo's November 1996 observations are consistent with wavelengths of Template:Nowrap and Template:Nowrap, and vertical amplitudes of Template:Nowrap and Template:Nowrap, for the larger and smaller sets of waves, respectively.<ref name = "Showalter"/> The formation of the larger set of waves can be explained if the ring was impacted by a cloud of particles released by the comet with a total mass on the order of 2–5 × 1012 kg, which would have tilted the ring out of the equatorial plane by 2 km.<ref name = "Showalter"/> A similar spiraling wave pattern that tightens over time<ref name = "tilting"> {{#invoke:citation/CS1|citation |CitationClass=web }}</ref> has been observed by Cassini in Saturns's C and D rings.<ref name = "Hedman2"> Template:Cite journal</ref>
Halo ringEdit
Appearance and structureEdit
The halo ring is the innermost and the vertically thickest Jovian ring. Its outer edge coincides with the inner boundary of the main ring approximately at the radius Template:Val (Template:Jupiter radius).<ref name=Ockert-Bell1999/><ref name=Burns1987/> From this radius the ring becomes rapidly thicker towards Jupiter. The true vertical extent of the halo is not known but the presence of its material was detected as high as Template:Val over the ring plane.<ref name=Ockert-Bell1999/><ref name=dePater1999/> The inner boundary of the halo is relatively sharp and located at the radius Template:Val (Template:Jupiter radius),<ref name=dePater1999/> but some material is present further inward to approximately Template:Val.<ref name=Ockert-Bell1999/> Thus the width of the halo ring is about Template:Val. Its shape resembles a thick torus without clear internal structure.<ref name=Burns2004/> In contrast to the main ring, the halo's appearance depends only slightly on the viewing geometry.
The halo ring appears brightest in forward-scattered light, in which it was extensively imaged by Galileo.<ref name=Ockert-Bell1999/> While its surface brightness is much less than that of the main ring, its vertically (perpendicular to the ring plane) integrated photon flux is comparable due to its much larger thickness. Despite a claimed vertical extent of more than Template:Val, the halo's brightness is strongly concentrated towards the ring plane and follows a power law of the form z−0.6 to z−1.5,<ref name=Burns2004/> where z is altitude over the ring plane. The halo's appearance in the back-scattered light, as observed by Keck<ref name=dePater1999>Template:Cite journal</ref> and HST,<ref name=Meier1999/> is the same. However its total photon flux is several times lower than that of the main ring and is more strongly concentrated near the ring plane than in the forward-scattered light.<ref name=Burns2004/>
The spectral properties of the halo ring are different from the main ring. The flux distribution in the range 0.5–2.5 μm is flatter than in the main ring;<ref name=Meier1999/> the halo is not red and may even be blue.<ref name=Wong2006/>
Origin of the halo ringEdit
The optical properties of the halo ring can be explained by the hypothesis that it comprises only dust with particle sizes less than 15 μm.<ref name=Meier1999/><ref name=Burns2004/><ref name=Brooks2004/> Parts of the halo located far from the ring plane may consist of submicrometre dust.<ref name=Meier1999/><ref name=dePater1999/><ref name=Burns2004/> This dusty composition explains the much stronger forward-scattering, bluer colors and lack of visible structure in the halo. The dust probably originates in the main ring, a claim supported by the fact that the halo's optical depth <math>\scriptstyle\tau_s\,\sim\,10^{-6}</math> is comparable with that of the dust in the main ring.<ref name=Burns1987/><ref name=Burns2004/> The large thickness of the halo can be attributed to the excitation of orbital inclinations and eccentricities of dust particles by the electromagnetic forces in the Jovian magnetosphere. The outer boundary of the halo ring coincides with location of a strong 3:2 Lorentz resonance.Template:Refn<ref name=Burns2001/><ref name=Hamilton1994>Template:Cite journal</ref><ref name=Burns1985>Template:Cite journal</ref> As Poynting–Robertson drag<ref name=Burns2001/><ref name=Burns1999/> causes particles to slowly drift towards Jupiter, their orbital inclinations are excited while passing through it. The bloom of the main ring may be a beginning of the halo.<ref name=Burns2004/> The halo ring's inner boundary is not far from the strongest 2:1 Lorentz resonance.<ref name=Burns2001/><ref name=Hamilton1994/><ref name=Burns1985/> In this resonance the excitation is probably very significant, forcing particles to plunge into the Jovian atmosphere thus defining a sharp inner boundary.<ref name=Burns2004/> Being derived from the main ring, the halo has the same age.<ref name=Burns2004/>
Gossamer ringsEdit
Amalthea gossamer ringEdit
The Amalthea gossamer ring is a very faint structure with a rectangular cross section, stretching from the orbit of Amalthea at Template:Val (2.54 RJ) to about Template:Val (Template:Jupiter radius).<ref name=Ockert-Bell1999/><ref name=Burns2004/> Its inner boundary is not clearly defined because of the presence of the much brighter main ring and halo.<ref name=Ockert-Bell1999/> The thickness of the ring is approximately 2300 km near the orbit of Amalthea and slightly decreases in the direction of Jupiter.Template:Refn<ref name=dePater1999/> The Amalthea gossamer ring is actually the brightest near its top and bottom edges and becomes gradually brighter towards Jupiter; one of the edges is often brighter than another.<ref name=Showalter2008>Template:Cite journal</ref> The outer boundary of the ring is relatively steep;<ref name=Ockert-Bell1999/> the ring's brightness drops abruptly just inward of the orbit of Amalthea,<ref name=Ockert-Bell1999/> although it may have a small extension beyond the orbit of the satellite ending near 4:3 resonance with Thebe.<ref name=dePater2008/> In forward-scattered light the ring appears to be about 30 times fainter than the main ring.<ref name=Ockert-Bell1999/> In back-scattered light it has been detected only by the Keck telescope<ref name=dePater1999/> and the ACS (Advanced Camera for Surveys) on HST.<ref name=Showalter2005/> Back-scattering images show additional structure in the ring: a peak in the brightness just inside the Amalthean orbit and confined to the top or bottom edge of the ring.<ref name=dePater1999/><ref name=dePater2008/>
In 2002–2003 Galileo spacecraft had two passes through the gossamer rings. During them its dust counter detected dust particles in the size range 0.2–5 μm.<ref name=Kruger2003/><ref name=Kruger2008>Template:Cite journal</ref> In addition, the Galileo spacecraft's star scanner detected small, discrete bodies (< 1 km) near Amalthea.<ref>Template:Cite journal</ref> These may represent collisional debris generated from impacts with this satellite.
The detection of the Amalthea gossamer ring from the ground, in Galileo images and the direct dust measurements have allowed the determination of the particle size distribution, which appears to follow the same power law as the dust in the main ring with q=2 ± 0.5.<ref name=Showalter2005/><ref name=Kruger2008/> The optical depth of this ring is about 10−7, which is an order of magnitude lower than that of the main ring, but the total mass of the dust (107–109 kg) is comparable.<ref name=Esposito2002/><ref name=Burns1999/><ref name=Kruger2008/>
Thebe gossamer ringEdit
The Thebe gossamer ring is the faintest Jovian ring. It appears as a very faint structure with a rectangular cross section, stretching from the Thebean orbit at Template:Val (Template:Jupiter radius) to about Template:Val (Template:Jupiter radius;).<ref name=Ockert-Bell1999/><ref name=Burns2004/> Its inner boundary is not clearly defined because of the presence of the much brighter main ring and halo.<ref name=Ockert-Bell1999/> The thickness of the ring is approximately 8400 km near the orbit of Thebe and slightly decreases in the direction of the planet.<ref group=lower-alpha name=footnoteF /><ref name=dePater1999/> The Thebe gossamer ring is brightest near its top and bottom edges and gradually becomes brighter towards Jupiter—much like the Amalthea ring.<ref name=Showalter2008/> The outer boundary of the ring is not especially steep, stretching over Template:Val.<ref name=Ockert-Bell1999/> There is a barely visible continuation of the ring beyond the orbit of Thebe, extending up to Template:Val (Template:Jupiter radius) and called the Thebe Extension.<ref name=Ockert-Bell1999/><ref name=Kruger2008/> In forward-scattered light the ring appears to be about 3 times fainter than the Amalthea gossamer ring.<ref name=Ockert-Bell1999/> In back-scattered light it has been detected only by the Keck telescope.<ref name=dePater1999/> Back-scattering images show a peak of brightness just inside the orbit of Thebe.<ref name=dePater1999/> In 2002–2003 the dust counter of the Galileo spacecraft detected dust particles in the size range 0.2–5 μm—similar to those in the Amalthea ring—and confirmed the results obtained from imaging.<ref name=Kruger2003>Template:Cite conference</ref><ref name=Kruger2008/>
The optical depth of the Thebe gossamer ring is about 3Template:E-sp, which is three times lower than the Amalthea gossamer ring, but the total mass of the dust is the same—about 107–109 kg.<ref name=Esposito2002/><ref name=Burns1999/><ref name=Kruger2008/> However the particle size distribution of the dust is somewhat shallower than in the Amalthea ring. It follows a power law with q < 2. In the Thebe extension the parameter q may be even smaller.<ref name=Kruger2008/>
Origin of the gossamer ringsEdit
The dust in the gossamer rings originates in essentially the same way as that in the main ring and halo.<ref name=Burns1999/> Its sources are the inner Jovian moons Amalthea and Thebe respectively. High velocity impacts by projectiles coming from outside the Jovian system eject dust particles from their surfaces.<ref name=Burns1999/> These particles initially retain the same orbits as their moons but then gradually spiral inward by Poynting–Robertson drag.<ref name=Burns1999/> The thickness of the gossamer rings is determined by vertical excursions of the moons due to their nonzero orbital inclinations.<ref name=Burns2004/> This hypothesis naturally explains almost all observable properties of the rings: rectangular cross-section, decrease of thickness in the direction of Jupiter and brightening of the top and bottom edges of the rings.<ref name=Showalter2008/>
However some properties have so far gone unexplained, like the Thebe Extension, which may be due to unseen bodies outside Thebe's orbit, and structures visible in the back-scattered light.<ref name=Burns2004/> One possible explanation of the Thebe Extension is influence of the electromagnetic forces from the Jovian magnetosphere. When the dust enters the shadow behind Jupiter, it loses its electrical charge fairly quickly. Since the small dust particles partially corotate with the planet, they will move outward during the shadow pass creating an outward extension of the Thebe gossamer ring.<ref name=Hamilton2008>Template:Cite journal</ref> The same forces can explain a dip in the particle distribution and ring's brightness, which occurs between the orbits of Amalthea and Thebe.<ref name=Kruger2008/><ref name=Hamilton2008/>
The peak in the brightness just inside of the Amalthea's orbit and, therefore, the vertical asymmetry the Amalthea gossamer ring may be due to the dust particles trapped at the leading (L4) and trailing (L5) Lagrange points of this moon.<ref name=Showalter2008/> The particles may also follow horseshoe orbits between the Lagrangian points.<ref name=dePater2008/> The dust may be present at the leading and trailing Lagrange points of Thebe as well. This discovery implies that there are two particle populations in the gossamer rings: one slowly drifts in the direction of Jupiter as described above, while another remains near a source moon trapped in 1:1 resonance with it.<ref name=Showalter2008/>
Himalia ringEdit
In September 2006, as NASA's New Horizons mission to Pluto approached Jupiter for a gravity assist, it photographed what appeared to be a faint, previously unknown planetary ring or ring arc, parallel with and slightly inside the orbit of the irregular satellite Himalia. The amount of material in the part of the ring or arc imaged by New Horizons was at least 0.04 km3, assuming it had the same albedo as Himalia. If the ring (arc) is debris from Himalia, it must have formed quite recently, given the century-scale precession of the Himalian orbit. It is possible that the ring could be debris from the impact of a very small undiscovered moon into Himalia, suggesting that Jupiter might continue to gain and lose small moons through collisions.<ref name="Cheng2010">Template:Cite conference</ref>
ExplorationEdit
The existence of the Jovian rings was inferred from observations of the planetary radiation belts by Pioneer 11 spacecraft in 1975.<ref name=Fillius1976>Template:Cite journal</ref> In 1979 the Voyager 1 spacecraft obtained a single overexposed image of the ring system.<ref name=Smith1979/> More extensive imaging was conducted by Voyager 2 in the same year, which allowed rough determination of the ring's structure.<ref name=Burns1987/> The superior quality of the images obtained by the Galileo orbiter between 1995 and 2003 greatly extended the existing knowledge about the Jovian rings.<ref name=Ockert-Bell1999/> Ground-based observation of the rings by the Keck<ref name=dePater1999/> telescope in 1997 and 2002 and the HST in 1999<ref name=Meier1999/> revealed the rich structure visible in back-scattered light. Images transmitted by the New Horizons spacecraft in February–March 2007<ref name="New Horizons"/> allowed observation of the fine structure in the main ring for the first time. In 2000, the Cassini spacecraft en route to Saturn conducted extensive observations of the Jovian ring system.<ref name=Brown2003>Template:Cite journal</ref> Future missions to the Jovian system will provide additional information about the rings.<ref name=Juno>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
GalleryEdit
- JupiterRings.jpg
The ring system as imaged by Galileo
- PIA21644 - Jupiter's rings from the inside.jpg
The rings as observed from the inside by Juno
- JWST photo of Jupiter and rings.png
James Webb Space Telescope's photo of Jupiter and rings in infrared at 2.12 and 3.23 μm
- Jupiter Showcases Auroras, Hazes (NIRCam Widefield View) (jupiter-auroras2).jpeg
James Web Telescope image of Jupiter, taken in Infrared light, reveals its faint rings, along with two moons, Amalthea and Adrastea, auroras, and features of its atmosphere.
See alsoEdit
NotesEdit
ReferencesEdit
External linksEdit
- Jupiter Rings Fact Sheet
- Jupiter's Rings by NASA's Solar System Exploration
- NASA Pioneer project page
- NASA Voyager project page
- NASA Galileo project page
- NASA Cassini project space
- New Horizons project page
- Planetary Ring Node: Jupiter's Ring System
- Rings of Jupiter nomenclature from the USGS planetary nomenclature page
Template:Planetary rings Template:Jupiter Template:Moons of Jupiter Template:Voyager program Template:Authority control Template:Featured article