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132-690: 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 and the system was more thoroughly investigated in the 1990s by the Galileo orbiter. The main ring has also been observed by the Hubble Space Telescope and from Earth for several years. Ground-based observation of

264-605: A heat shield for an atmospheric probe did not yet exist, and facilities to test one under the conditions found on Jupiter would not be available until 1980. NASA management designated the Jet Propulsion Laboratory (JPL) as the lead center for the Jupiter Orbiter Probe (JOP) project. The JOP would be the fifth spacecraft to visit Jupiter, but the first to orbit it, and the probe would be the first to enter its atmosphere. An important decision made at this time

396-1007: A substellar object with a circumstellar disk or massive rings transiting the star. This substellar object, dubbed " J1407b ", is most likely a free-floating brown dwarf or rogue planet several times the mass of Jupiter. The circumstellar disk or ring system of J1407b is about 0.6 astronomical units (90,000,000 km; 56,000,000 mi) in radius. J1407b's transit of V1400 Centauri revealed gaps and density variations within its disk or ring system, which has been interpreted as hints of exomoons or exoplanets forming around J1407b. Solar System   → Local Interstellar Cloud   → Local Bubble   → Gould Belt   → Orion Arm   → Milky Way   → Milky Way subgroup   → Local Group → Local Sheet → Virgo Supercluster → Laniakea Supercluster   → Local Hole   → Observable universe   → Universe Each arrow ( → ) may be read as "within" or "part of". Galileo (spacecraft) Galileo

528-465: A 250 mm (9.8 in) aperture. Both the UVS and EUV instruments used a ruled grating to disperse light for spectral analysis. Light then passed through an exit slit into photomultiplier tubes that produced pulses of electrons, which were counted and the results sent to Earth. The UVS was mounted on Galileo 's scan platform. The EUV was mounted on the spun section. As Galileo rotated, EUV observed

660-424: A 5-meter long (16 ft) boom, carried 7.8 kilograms (17 lb) of Pu . Each RTG contained 18 separate heat source modules, and each module encased four pellets of plutonium(IV) oxide , a ceramic material resistant to fracturing. The plutonium was enriched to about 83.5 percent plutonium-238. The modules were designed to survive a range of potential accidents: launch vehicle explosion or fire, re-entry into

792-447: A broader color detection band than the vidicons of Voyager . The SSI was an 800-by-800-pixel charge-coupled device (CCD) camera. The optical portion of the camera was a modified flight spare of the Voyager narrow-angle camera; a Cassegrain telescope . The CCD had radiation shielding a 10 mm (0.4 in) thick layer of tantalum surrounding the CCD except where the light enters

924-471: A considerable risk to the New Horizons spacecraft. However, this possibility was ruled out when New Horizons failed to detect any dust rings around Pluto. 10199 Chariklo , a centaur , was the first minor planet discovered to have rings. It has two rings , perhaps due to a collision that caused a chain of debris to orbit it. The rings were discovered when astronomers observed Chariklo passing in front of

1056-478: A dense ringlet. 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 1,000 – 3,000 km . 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. They may be wavelike structures excited by this interaction. Spectra of

1188-428: A distance of 4,057 ± 6 km , approximately 7.5 times the radius of Quaoar and more than double the distance of its Roche limit. The inner ring orbits at a distance of 2,520 ± 20 km , approximately 4.6 times the radius of Quaoar and also beyond its Roche limit. The outer ring appears to be inhomogeneous, containing a thin, dense section as well as a broader, more diffuse section. Because all giant planets of

1320-571: A distinctive band around the Earth's equator at that time. The presence of this ring may have led to significant shielding of Earth from sun's rays and a severe cooling event, thus causing the Hirnantian glaciation , the coldest known period of the last 450 million years. Reports in March 2008 suggested that Saturn's moon Rhea may have its own tenuous ring system , which would make it the only moon known to have

1452-431: A faulty main engine controller that forced a postponement to October 17, and then by inclement weather, which necessitated a postponement to the following day, but this was not a concern since the launch window extended until November 21. Atlantis finally lifted off at 16:53:40 UTC on October 18, and went into a 343-kilometer (213 mi) orbit. Galileo was successfully deployed at 00:15 UTC on October 19. Following

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1584-552: A fixed axis or by maintaining a fixed orientation with reference to the Sun and a star. Galileo did both. One section of the spacecraft rotated at 3 revolutions per minute, keeping Galileo stable and holding six instruments that gathered data from many different directions, including the fields and particles instruments. Galileo was intentionally destroyed in Jupiter's atmosphere on September 21, 2003. The next orbiter to be sent to Jupiter

1716-501: 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 128,500 km . 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. Inward of the orbit of Metis,

1848-624: A high-energy particle detector; and a detector of cosmic and Jovian dust . It also carried the Heavy Ion Counter, an engineering experiment to assess the potentially hazardous charged particle environments the spacecraft flew through, and an extreme ultraviolet detector associated with the UV spectrometer on the scan platform. The despun section's instruments included the camera system; the near infrared mapping spectrometer to make multi-spectral images for atmospheric and moon surface chemical analysis;

1980-408: A moon that was disrupted by tidal stresses when it passed within the planet's Roche limit. Most rings were thought to be unstable and to dissipate over the course of tens or hundreds of millions of years, but it now appears that Saturn's rings might be quite old, dating to the early days of the Solar System. Fainter planetary rings can form as a result of meteoroid impacts with moons orbiting around

2112-413: A narrow ribbon of space perpendicular to the spin axis. The two instruments combined weighed about 9.7 kg (21 lb) and used 5.9 watts of power. The PPR had seven radiometry bands. One of these used no filters and observed all incoming radiation, both solar and thermal. Another band allowed only solar radiation through. The difference between the solar-plus-thermal and the solar-only channels gave

2244-455: A planetary ring in about 50 million years. Its low orbit, with an orbital period that is shorter than a Martian day, is decaying due to tidal deceleration . Jupiter's ring system was the third to be discovered, when it was first observed by the Voyager 1 probe in 1979, and was observed more thoroughly by the Galileo orbiter in the 1990s. Its four main parts are a faint thick torus known as

2376-404: A ring mass of 0.1%−10% of the centaur's mass is predicted. Ring formation from an undifferentiated body is less likely. The rings would be composed mostly or entirely of material from the parent body's icy mantle. After forming, the ring would spread laterally, leading to satellite formation from whatever portion of it spreads beyond the centaur's Roche Limit. Satellites could also form directly from

2508-468: A ring particle is determined by the specific strength of the material it is made of, its density, and the tidal force at its altitude. The tidal force is proportional to the average density inside the radius of the ring, or to the mass of the planet divided by the radius of the ring cubed. It is also inversely proportional to the square of the orbital period of the ring. Some planetary rings are influenced by shepherd moons , small moons that orbit near

2640-486: A ring system for a period of 40 million years, starting from the middle of the Ordovician period (around 466 million years ago). This ring system may have originated from a large asteroid that passed by Earth at this time and had a significant amount of debris stripped by Earth's gravitational pull, forming a ring system. Evidence for this ring comes from impact craters from the Ordovician meteor event appearing to cluster in

2772-571: A ring system. A later study published in 2010 revealed that imaging of Rhea by the Cassini spacecraft was inconsistent with the predicted properties of the rings, suggesting that some other mechanism is responsible for the magnetic effects that had led to the ring hypothesis. Prior to the arrival of New Horizons , some astronomers hypothesized that Pluto and Charon might have a circumbinary ring system created from dust ejected off of Pluto's small outer moons in impacts. A dust ring would have posed

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2904-528: A series of filters, and, from there, measurements were performed by the detectors of the PPR. The PPR weighed 5.0 kg (11.0 lb) and consumed about 5 watts of power. The dust-detector subsystem (DDS) was used to measure the mass, electric charge, and velocity of incoming particles. The masses of dust particles that the DDS could detect go from 10 to 10 grams. The speed of these small particles could be measured over

3036-438: A series of tiny ringlets as many think, but are more of a disk with varying density. They consist mostly of water ice and trace amounts of rock , and the particles range in size from micrometers to meters. Uranus's ring system lies between the level of complexity of Saturn's vast system and the simpler systems around Jupiter and Neptune. They were discovered in 1977 by James L. Elliot , Edward W. Dunham, and Jessica Mink . In

3168-401: 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. The distribution of large bodies in the mm–km size range is undetermined presently. The light scattering in this model is dominated by particles with r around 15 μm. The power law mentioned above allows estimation of

3300-556: Is about 1,000 times closer than the Moon is to Earth. In addition, astronomers suspect there could be a moon orbiting amidst the ring debris. If these rings are the leftovers of a collision as astronomers suspect, this would give fodder to the idea that moons (such as the Moon) form through collisions of smaller bits of material. Chariklo's rings have not been officially named, but the discoverers have nicknamed them Oiapoque and Chuí, after two rivers near

3432-435: Is about 2 × 10 kg, Amalthea, about 2 × 10 kg, and Earth's Moon , 7.4 × 10 kg. The presence of two populations of particles in the main ring explains why its appearance depends on the viewing geometry. The dust scatters light preferably in the forward direction and forms a relatively thick homogenous ring bounded by the orbit of Adrastea. In contrast, large particles, which scatter in

3564-450: Is comparable. 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 226 000  km ( 3.11   R J ) to about 129 000  km ( 1.80   R J ;). Its inner boundary is not clearly defined because of the presence of the much brighter main ring and halo. The thickness of

3696-404: Is currently unknown, but it may be the last remnant of a past population of small bodies near Jupiter . 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,

3828-414: 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 20 000  km , the halo's brightness is strongly concentrated towards the ring plane and follows a power law of the form z to z , where z is altitude over the ring plane. The halo's appearance in

3960-426: Is not clearly defined because of the presence of the much brighter main ring and halo. The thickness of the ring is approximately 2300 km near the orbit of Amalthea and slightly decreases in the direction of Jupiter . 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. The outer boundary of

4092-486: Is possible that it has existed since the formation of Jupiter. 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. 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

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4224-430: Is present further inward to approximately 92 000  km . Thus the width of the halo ring is about 30 000  km . Its shape resembles a thick torus without clear internal structure. 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 . While its surface brightness

4356-498: Is well within Haumea's Roche limit , which would lie at a radius of about 4,400 km if Haumea were spherical (being nonspherical pushes the limit out farther). In 2023, astronomers announced the discovery of a widely separated ring around the dwarf planet and Kuiper belt object Quaoar . Further analysis of the occultation data uncovered a second inner, fainter ring. Both rings display unusual properties. The outer ring orbits at

4488-443: The Voyager 1 space probe . 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. The principal attributes of the known Jovian Rings are listed in the table. In 2022, dynamical simulations suggested that

4620-513: The 6502 that was being built into the Apple II desktop computer at that time. The Galileo Attitude and Articulation Control System (AACSE) was controlled by two Itek Advanced Technology Airborne Computers (ATAC), built using radiation-hardened 2901s . The AACSE could be reprogrammed in flight by sending the new program through the Command and Data Subsystem. The attitude control system software

4752-550: The asteroid belt or Kuiper belt , or rings of interplanetary dust , such as around the Sun at distances of Mercury , Venus , and Earth, in mean motion resonance with these planets. Evidence suggests that ring systems may also be found around other types of astronomical objects, including moons and brown dwarfs . In the Solar System , all four giant planets ( Jupiter , Saturn, Uranus , and Neptune ) have ring systems. Ring systems around minor planets have also been discovered via occultations. Some studies even theorize that

4884-483: The optical depth τ {\displaystyle \scriptstyle \tau } of the main ring: τ l = 4.7 × 10 − 6 {\displaystyle \scriptstyle \tau _{l}\,=\,4.7\times 10^{-6}} for the large bodies and τ s = 1.3 × 10 − 6 {\displaystyle \scriptstyle \tau _{s}=1.3\times 10^{-6}} for

5016-439: The "halo"; a thin, relatively bright main ring; and two wide, faint "gossamer rings". The system consists mostly of dust. Saturn's rings are the most extensive ring system of any planet in the Solar System, and thus have been known to exist for quite some time. Galileo Galilei first observed them in 1610, but they were not accurately described as a disk around Saturn until Christiaan Huygens did so in 1655. The rings are not

5148-523: The Adrastean orbit) and reaches the background level at 129,300 km —just outward of the Adrastean orbit. Therefore, Adrastea at 129,000 km clearly shepherds the ring. The brightness continues to increase in the direction of Jupiter and has a maximum near the ring's center at 126,000 km , although there is a pronounced gap (notch) near the Metidian orbit at 128,000 km . The inner boundary of

5280-473: 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. The optical depth of this ring is about 10, which is an order of magnitude lower than that of the main ring, but the total mass of the dust (10–10 kg)

5412-459: The EUV shared a communications link and, therefore, had to share observing time. The HIC weighed 8.0 kg (17.6 lb) and used an average of 2.8 watts of power. The magnetometer (MAG) used two sets of three sensors. The three sensors allowed the three orthogonal components of the magnetic field section to be measured. One set was located at the end of the magnetometer boom and, in that position,

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5544-448: The Earth may have had a ring system during the mid-late Ordovician period. There are three ways that thicker planetary rings have been proposed to have formed: from material originating from the protoplanetary disk that was within the Roche limit of the planet and thus could not coalesce to form moons, from the debris of a moon that was disrupted by a large impact, or from the debris of

5676-505: 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. The optical depth of the Thebe gossamer ring is about 3 × 10, which is three times lower than the Amalthea gossamer ring, but the total mass of the dust is the same—about 10–10 kg. However the particle size distribution of

5808-492: The IUS burn, the Galileo spacecraft adopted its configuration for solo flight, and separated from the IUS at 01:06:53 UTC on October 19. The launch was perfect, and Galileo was soon headed towards Venus at over 14,000 km/h (9,000 mph). Atlantis returned to Earth safely on October 23. The CDH subsystem was actively redundant, with two parallel data system buses running at all times. Each data system bus (a.k.a. string)

5940-920: The JPL in Pasadena, California , on the first leg of its journey, a road trip to the Kennedy Space Center in Florida . Due to the Space Shuttle Challenger disaster , the May launch date could not be met. The mission was rescheduled to October 12, 1989. The Galileo spacecraft would be launched by the STS-34 mission in the Space Shuttle Atlantis . As the launch date of Galileo neared, anti-nuclear groups , concerned over what they perceived as an unacceptable risk to

6072-448: The Jovian ring system. Future missions to the Jovian system will provide additional information about the rings. Planetary ring Ring systems are best known as planetary rings, common components of satellite systems around giant planets such as of Saturn , or circumplanetary disks . But they can also be galactic rings and circumstellar discs , belts of planetoids, such as

6204-452: The Jovian rings was inferred from observations of the planetary radiation belts by Pioneer 11 spacecraft in 1975. In 1979 the Voyager 1 spacecraft obtained a single overexposed image of the ring system. More extensive imaging was conducted by Voyager 2 in the same year, which allowed rough determination of the ring's structure. The superior quality of the images obtained by the Galileo orbiter between 1995 and 2003 greatly extended

6336-451: The Jovian system eject dust particles from their surfaces. These particles initially retain the same orbits as their moons but then gradually spiral inward by Poynting–Robertson drag . The thickness of the gossamer rings is determined by vertical excursions of the moons due to their nonzero orbital inclinations . This hypothesis naturally explains almost all observable properties of the rings: rectangular cross-section, decrease of thickness in

6468-562: The Mariner and Voyager projects, became the first project manager. He solicited suggestions for a more inspirational name for the project, and the most votes went to "Galileo" after Galileo Galilei , the first person to view Jupiter through a telescope. His 1610 discovery of what is now known as the Galilean moons orbiting Jupiter was important evidence of the Copernican model of the solar system. It

6600-417: The Solar System have rings, the existence of exoplanets with rings is plausible. Although particles of ice , the material that is predominant in the rings of Saturn , can only exist around planets beyond the frost line , within this line rings consisting of rocky material can be stable in the long term. Such ring systems can be detected for planets observed by the transit method by additional reduction of

6732-503: The atmosphere followed by land or water impact, and post-impact situations. An outer covering of graphite provided protection against the structural, thermal, and eroding environments of a potential re-entry into Earth's atmosphere. Additional graphite components provided impact protection, while iridium cladding of the RTGs provided post-impact containment. The RTGs produced about 570 watts at launch. The power output initially decreased at

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6864-457: The back direction, are confined in a number of ringlets between the Metidian and Adrastean orbits. The dust is constantly being removed from the main ring by a combination of Poynting–Robertson drag and electromagnetic forces from the Jovian magnetosphere . Volatile materials such as ices, for example, evaporate quickly. The lifetime of dust particles in the ring is from 100 to 1,000 years , so

6996-408: The back-scattered light, as observed by Keck and HST , 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. 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;

7128-520: 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 (L 4 ) and trailing (L 5 ) Lagrange points of this moon. The particles may also follow horseshoe orbits between the Lagrangian points. 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

7260-403: The brightness of the ring rises much less than in forward-scattered light. So in the back-scattered geometry the main ring appears to consist of two different parts: a narrow outer part extending from 128,000 to 129,000 km , which itself includes three narrow ringlets separated by notches, and a fainter inner part from 122,500 to 128,000 km , which lacks any visible structure like in

7392-460: The direction of Jupiter and brightening of the top and bottom edges of the rings. 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. One possible explanation of the Thebe Extension is influence of the electromagnetic forces from the Jovian magnetosphere. When

7524-405: 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. The bloom grows in thickness towards the inner boundary of the main ring, where it transitions into the halo. Detailed analysis of the Galileo images revealed longitudinal variations of the main ring's brightness unconnected with

7656-491: The disrupted icy mantle. This formation mechanism predicts that roughly 10% of centaurs will have experienced potentially ring-forming encounters with giant planets. The composition of planetary ring particles varies, ranging from silicates to icy dust. Larger rocks and boulders may also be present, and in 2007 tidal effects from eight moonlets only a few hundred meters across were detected within Saturn's rings. The maximum size of

7788-415: 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. The same forces can explain a dip in the particle distribution and ring's brightness, which occurs between the orbits of Amalthea and Thebe. The peak in

7920-401: 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. The dust in the gossamer rings originates in essentially the same way as that in the main ring and halo. Its sources are the inner Jovian moons Amalthea and Thebe respectively. High velocity impacts by projectiles coming from outside

8052-466: The dust must be continuously replenished in the collisions between large bodies with sizes from 1 cm to 0.5 km and between the same large bodies and high velocity particles coming from outside the Jovian system. This parent body population is confined to the narrow—about 1,000 km —and bright outer part of the main ring, and includes Metis and Adrastea. The largest parent bodies must be less than 0.5 km in size. The upper limit on their size

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8184-487: The dust. This optical depth means that the total cross section of all particles inside the ring is about 5000 km². The particles in the main ring are expected to have aspherical shapes. The total mass of the dust is estimated to be 10−10 kg. The mass of large bodies, excluding Metis and Adrastea, is 10−10 kg. It depends on their maximum size— the upper value corresponds to about 1 km maximum diameter. These masses can be compared with masses of Adrastea, which

8316-402: The electromagnetic forces in the Jovian magnetosphere. The outer boundary of the halo ring coincides with location of a strong 3:2 Lorentz resonance. As Poynting–Robertson drag 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. The halo ring's inner boundary is not far from

8448-773: The energetic particle population at Jupiter as a function of position and time. These measurements helped determine how the particles got their energy and how they were transported through Jupiter's magnetosphere. The EPD weighed 10.5 kg (23 lb) and used 10.1 watts of power on average. The HIC was, in effect, a repackaged and updated version of some parts of the flight spare of the Voyager cosmic-ray system. The HIC detected heavy ions using stacks of single crystal silicon wafers. The HIC could measure heavy ions with energies as low as 6 MeV (1 pJ) and as high as 200 MeV (32 pJ) per nucleon. This range included all atomic substances between carbon and nickel . The HIC and

8580-603: The existing knowledge about the Jovian rings. Ground-based observation of the rings by the Keck telescope in 1997 and 2002 and the HST in 1999 revealed the rich structure visible in back-scattered light. Images transmitted by the New Horizons spacecraft in February–March 2007 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

8712-508: The fields and particles instruments. Back on the ground, the mission operations team used software containing 650,000 lines of code in the orbit sequence design process; 1,615,000 lines in the telemetry interpretation; and 550,000 lines of code in navigation. All of the spacecraft components and spare parts received a minimum of 2,000 hours of testing. The spacecraft was expected to last for at least five years—long enough to reach Jupiter and perform its mission. On December 19, 1985, it departed

8844-485: The fine structure was observed by the Keck telescope using adaptive optics in 2002–2003. Observed in back-scattered light the main ring appears to be razor thin, extending in the vertical direction no more than 30 km. In the side scatter geometry the ring thickness is 80–160 km, increasing somewhat in the direction of Jupiter . The ring appears to be much thicker in the forward-scattered light—about 300 km. One of

8976-433: The first trans-Neptunian object found to have a ring system. The ring has a radius of about 2,287 km , a width of ≈ 70 km and an opacity of 0.5. The ring plane coincides with Haumea's equator and the orbit of its larger, outer moon Hi’iaka (which has a semimajor axis of ≈ 25,657 km ). The ring is close to the 3:1 resonance with Haumea's rotation, which is located at a radius of 2,285 ± 8 km . It

9108-535: The first spacecraft to orbit an outer planet. The Jet Propulsion Laboratory built the Galileo spacecraft and managed the Galileo program for NASA . West Germany's Messerschmitt-Bölkow-Blohm supplied the propulsion module. NASA's Ames Research Center managed the atmospheric probe, which was built by Hughes Aircraft Company . At launch, the orbiter and probe together had a mass of 2,562 kg (5,648 lb) and stood 6.15 m (20.2 ft) tall. Spacecraft are normally stabilized either by spinning around

9240-533: The following functions: The propulsion subsystem consisted of a 400 N (90 lbf) main engine and twelve 10 N (2.2 lbf) thrusters, together with propellant, storage and pressurizing tanks and associated plumbing. The 10 N thrusters were mounted in groups of six on two 2-meter (6.6 ft) booms. The fuel for the system was 925 kg (2,039 lb) of monomethylhydrazine and nitrogen tetroxide . Two separate tanks held another 7 kg (15 lb) of helium pressurant. The propulsion subsystem

9372-422: The following functions: The spacecraft was controlled by six RCA 1802 COSMAC microprocessor CPUs : four on the spun side and two on the despun side. Each CPU was clocked at about 1.6 MHz, and fabricated on sapphire ( silicon on sapphire ), which is a radiation-and static-hardened material ideal for spacecraft operation. This 8-bit microprocessor was the first low-power CMOS processor chip, similar to

9504-439: The forward-scattering geometry. 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. The early observations by Hubble Space Telescope (HST), Keck and the Cassini spacecraft failed to detect it, probably due to insufficient spatial resolution. However

9636-407: 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. 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

9768-431: The halo is not red and may even be blue. 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. Parts of the halo located far from the ring plane may consist of submicrometre dust. This dusty composition explains the much stronger forward-scattering, bluer colors and lack of visible structure in the halo. The dust probably originates in

9900-460: The inner boundary of the main ring approximately at the radius 122 500  km ( 1.72   R J ). 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 10 000  km over the ring plane. The inner boundary of the halo is relatively sharp and located at the radius 100 000  km ( 1.4   R J ), but some material

10032-403: The inner or outer edges of a ringlet or within gaps in the rings. The gravity of shepherd moons serves to maintain a sharply defined edge to the ring; material that drifts closer to the shepherd moon's orbit is either deflected back into the body of the ring, ejected from the system, or accreted onto the moon itself. It is also predicted that Phobos , a moon of Mars, will break up and form into

10164-587: 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 km, 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. The existence of

10296-512: 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 × 10 kg, which would have tilted the ring out of the equatorial plane by 2 km. A similar spiraling wave pattern that tightens over time has been observed by Cassini in Saturns's C and D rings. The halo ring is the innermost and the vertically thickest Jovian ring. Its outer edge coincides with

10428-425: The light of the central star if their opacity is sufficient. As of 2024, two candidate extrasolar ring systems have been found by this method, around HIP 41378 f and K2-33b . Fomalhaut b was found to be large and unclearly defined when detected in 2008. This was hypothesized to either be due to a cloud of dust attracted from the dust disc of the star, or a possible ring system, though in 2020 Fomalhaut b itself

10560-479: The long-term variation in Chiron's brightness over time. Chiron's rings are suspected to be maintained by orbiting material ejected during seasonal outbursts, as a third partial ring detected in 2018 had become a full ring by 2022, with an outburst in between in 2021. A ring around Haumea , a dwarf planet and resonant Kuiper belt member , was revealed by a stellar occultation observed on 21 January 2017. This makes it

10692-475: The low-density regions of Saturn's rings. However, they are faint and dusty, much more similar in structure to those of Jupiter. The very dark material that makes up the rings is likely organics processed by radiation , like in the rings of Uranus. 20 to 70 percent of the rings are dust , a relatively high proportion. Hints of the rings were seen for decades prior to their conclusive discovery by Voyager 2 in 1989. A 2024 study suggests that Earth may have had

10824-433: The magnetic fields. The electric dipole antenna was mounted at the tip of the magnetometer boom. The search coil magnetic antennas were mounted on the high-gain antenna feed. Nearly simultaneous measurements of the electric and magnetic field spectrum allowed electrostatic waves to be distinguished from electromagnetic waves . The PWS weighed 7.1 kg (16 lb) and used an average of 9.8 watts. The atmospheric probe

10956-416: The main ring are very similar to Adrastea and Amalthea. 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. However, larger bodies are required to explain the strong back-scattering and fine structure in the bright outer part of

11088-490: The main ring obtained by the HST , Keck , Galileo and Cassini 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. 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. The spectra of

11220-423: The main ring, a claim supported by the fact that the halo's optical depth τ s ∼ 10 − 6 {\displaystyle \scriptstyle \tau _{s}\,\sim \,10^{-6}} is comparable with that of the dust in the main ring. The large thickness of the halo can be attributed to the excitation of orbital inclinations and eccentricities of dust particles by

11352-399: The main ring, in contrast, appears to fade off slowly from 124,000 to 120,000 km , merging into the halo ring. In forward-scattered light all Jovian rings are especially bright. In back-scattered light the situation is different. The outer boundary of the main ring, located at 129,100 km , or slightly beyond the orbit of Adrastea, is very steep. The orbit of the moon is marked by

11484-423: The main ring. 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 where n ( r )  dr is a number of particles with radii between r and r  +  dr and A {\displaystyle A} is a normalizing parameter chosen to match the known total light flux from the ring. The parameter q

11616-506: The moons Metis , Adrastea and perhaps smaller, unobserved bodies as the result of high-velocity impacts. High-resolution images obtained in February and March 2007 by the New Horizons spacecraft revealed a rich fine structure in the main ring. In visible and near-infrared light, the rings have a reddish color, except the halo ring, which is neutral or blue in color. The size of the dust in

11748-456: 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. Galileo' s November 1996 observations are consistent with wavelengths of 1920 ± 150 and 630 ± 20 km , and vertical amplitudes of 2.4 ± 0.7 and 0.6 ± 0.2 km , for the larger and smaller sets of waves, respectively. The formation of

11880-437: The northern and southern ends of Brazil. A second centaur, 2060 Chiron , has a constantly evolving disk of rings. Based on stellar-occultation data that were initially interpreted as resulting from jets associated with Chiron's comet-like activity, the rings are proposed to be 324 ± 10 km in radius, though their evolution does change the radius somewhat. Their changing appearance at different viewing angles can explain

12012-423: The orbit of Jupiter's smallest inner satellite, Adrastea . Its inner edge is not marked by any satellite and is located at about 122,500 km ( 1.72   R J ). Thus the width of the main ring is around 6,500 km . The appearance of the main ring depends on the viewing geometry. In forward-scattered light the brightness of the main ring begins to decrease steeply at 128,600 km (just inward of

12144-405: The orbit of Thebe, extending up to 280 000  km ( 3.75   R J ) and called the Thebe Extension. In forward-scattered light the ring appears to be about 3 times fainter than the Amalthea gossamer ring. In back-scattered light it has been detected only by the Keck telescope. Back-scattering images show a peak of brightness just inside the orbit of Thebe. In 2002–2003 the dust counter of

12276-468: The orbiter and probe together had a mass of 2,562 kg (5,648 lb) and stood 6.15 m (20.2 ft) tall. Spacecraft are normally stabilized either by spinning around a fixed axis or by maintaining a fixed orientation with reference the Sun and a star; Galileo did both. One section of the spacecraft rotated at 3 revolutions per minute , keeping Galileo stable and holding six instruments that gathered data from many different directions, including

12408-464: The outboard (11 m) set of sensors could measure magnetic field strengths in the range from ±32 to ±512 nT, while the inboard (6.7 m) set was active in the range from ±512 to ±16,384 nT. The MAG experiment weighed 7.0 kg (15.4 lb) and used 3.9 watts of power. The PLS used seven fields of view to collect charged particles for energy and mass analysis. These fields of view covered most angles from 0 to 180 degrees, fanning out from

12540-399: The planet or, in the case of Saturn's E-ring, the ejecta of cryovolcanic material. Ring systems may form around centaurs when they are tidally disrupted in a close encounter (within 0.4 to 0.8 times the Roche limit ) with a giant planet. For a differentiated body approaching a giant planet at an initial relative velocity of 3−6 km/s with an initial rotational period of 8 hours,

12672-413: The propulsion module and most of Galileo 's computers and control electronics. The sixteen instruments, weighing 118 kg (260 lb) altogether, included magnetometer sensors mounted on an 11 m (36 ft) boom to minimize interference from the spacecraft; a plasma instrument for detecting low-energy charged particles and a plasma-wave detector to study waves generated by the particles;

12804-403: The public's safety from the plutonium in the Galileo 's radioisotope thermoelectric generators (RTGs) and General Purpose Heat Source (GPHS) modules, sought a court injunction prohibiting Galileo 's launch. RTGs were necessary for deep space probes because they had to fly distances from the Sun that made the use of solar energy impractical. The launch was delayed twice more: by

12936-402: The range of 1 to 70 kilometers per second (0.6 to 43.5 mi/s). The instrument could measure impact rates from 1 particle per 115 days (10 megaseconds) to 100 particles per second. Such data was used to help determine dust origin and dynamics within the magnetosphere . The DDS weighed 4.2 kg (9.3 lb) and used an average of 5.4 watts of power. The energetic-particles detector (EPD)

13068-426: The rate of 0.6 watts per month and was 493 watts when Galileo arrived at Jupiter. The spacecraft had a large high-gain antenna which failed to deploy while in space, so the low-gain antenna was used instead, although at slower data transfer speeds. Scientific instruments to measure fields and particles were mounted on the spinning section of the spacecraft, together with the main antenna , power supply,

13200-427: 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 . 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 129,000 km ( 1.806   R J ; R J = equatorial radius of Jupiter or 71,398 km ) and coincides with

13332-411: The ring is approximately 8400 km near the orbit of Thebe and slightly decreases in the direction of the planet. The Thebe gossamer ring is brightest near its top and bottom edges and gradually becomes brighter towards Jupiter —much like the Amalthea ring. The outer boundary of the ring is not especially steep, stretching over 15 000  km . There is a barely visible continuation of the ring beyond

13464-534: The ring is relatively steep; the ring's brightness drops abruptly just inward of the orbit of Amalthea, although it may have a small extension beyond the orbit of the satellite ending near 4:3 resonance with Thebe. In forward-scattered light the ring appears to be about 30 times fainter than the main ring. In back-scattered light it has been detected only by the Keck telescope and the ACS ( Advanced Camera for Surveys ) on HST . Back-scattering images show additional structure in

13596-550: The ring: a peak in the brightness just inside the Amalthean orbit and confined to the top or bottom edge of the ring. 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. In addition, the Galileo spacecraft's star scanner detected small, discrete bodies (< 1 km) near Amalthea. These may represent collisional debris generated from impacts with this satellite. The detection of

13728-448: The rings requires the largest available telescopes. The Jovian ring system is faint and consists mainly of dust. 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 . The main and halo rings consist of dust ejected from

13860-400: The rings varies, but the cross-sectional area is greatest for nonspherical particles of radius about 15 μm in all rings except the halo. 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 10 to 10 kg. The age of the ring system is also not known, but it

13992-417: The spin axis. The rotation of the spacecraft carried each field of view through a full circle. The PLS measured particles in the energy range from 0.9 to 52,000  eV (0.14 to 8,300  aJ ). The PLS weighed 13.2 kg (29 lb) and used an average of 10.7 watts of power. An electric dipole antenna was used to study the electric fields of plasmas , while two search coil magnetic antennas studied

14124-492: The star UCAC4 248-108672 on June 3, 2013 from seven locations in South America. While watching, they saw two dips in the star's apparent brightness just before and after the occultation. Because this event was observed at multiple locations, the conclusion that the dip in brightness was in fact due to rings is unanimously the leading hypothesis. The observations revealed what is likely a 19-kilometer (12-mile)-wide ring system that

14256-491: The strongest 2:1 Lorentz resonance. In this resonance the excitation is probably very significant, forcing particles to plunge into the Jovian atmosphere thus defining a sharp inner boundary. Being derived from the main ring, the halo has the same age. The Amalthea gossamer ring is a very faint structure with a rectangular cross section, stretching from the orbit of Amalthea at 182 000  km (2.54 R J ) to about 129 000  km ( 1.80   R J ). Its inner boundary

14388-483: The system. An eight-position filter wheel was used to obtain images at specific wavelengths. The images were then combined electronically on Earth to produce color images. The spectral response of the SSI ranged from about 400 to 1100 nm. The SSI weighed 29.7 kg (65 lb) and consumed, on average, 15 watts of power. The NIMS instrument was sensitive to 0.7-to-5.2- micrometer wavelength infrared light, overlapping

14520-502: The time between then and 2005, observations by Voyager 2 and the Hubble Space Telescope led to a total of 13 distinct rings being identified, most of which are opaque and only a few kilometers wide. They are dark and likely consist of water ice and some radiation-processed organics . The relative lack of dust is due to aerodynamic drag from the extended exosphere - corona of Uranus. The system around Neptune consists of five principal rings that, at their densest, are comparable to

14652-486: The total thermal radiation emitted. The PPR also measured in five broadband channels that spanned the spectral range from 17 to 110 micrometers. The radiometer provided data on the temperatures of Jupiter's atmosphere and satellites. The design of the instrument was based on that of an instrument flown on the Pioneer Venus spacecraft. A 100 mm (4 in) aperture reflecting telescope collected light and directed it to

14784-425: The ultraviolet spectrometer to study gases; and the photopolarimeter-radiometer to measure radiant and reflected energy. The camera system was designed to obtain images of Jupiter's satellites at resolutions 20 to 1,000 times better than Voyager 's best, because Galileo flew closer to the planet and its inner moons, and because the more modern CCD sensor in Galileo 's camera was more sensitive and had

14916-416: The viewing geometry. The Galileo images also showed some patchiness in the ring on the scales 500–1000 km. In February–March 2007 New Horizons spacecraft conducted a deep search for new small moons inside the main ring. 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

15048-403: The wavelength range of the SSI. NIMS used a 229 mm (9 in) aperture reflecting telescope. The spectrometer used a grating to disperse the light collected by the telescope. The dispersed spectrum of light was focused on detectors of indium , antimonide and silicon . NIMS weighed 18 kg (40 lb) and used 12 watts of power on average. The Cassegrain telescope of the UVS had

15180-418: Was Juno , which arrived on July 5, 2016. Jupiter is the largest planet in the Solar System , with more than twice the mass of all the other planets combined. Consideration of sending a probe to Jupiter began as early as 1959. NASA's Scientific Advisory Group (SAG) for Outer Solar System Missions considered the requirements for Jupiter orbiters and atmospheric probes. It noted that the technology to build

15312-455: Was about 11 m (36 ft) from the spin axis of the spacecraft. The second set, designed to detect stronger fields, was 6.7 m (22 ft) from the spin axis. The boom was used to remove the MAG from the immediate vicinity of Galileo to minimize magnetic effects from the spacecraft. However, not all these effects could be eliminated by distancing the instrument. The rotation of the spacecraft

15444-499: Was also noted that the name was that of a spacecraft in the Star Trek television show. The new name was adopted in February 1978. The Jet Propulsion Laboratory built the Galileo spacecraft and managed the Galileo mission for NASA. West Germany 's Messerschmitt-Bölkow-Blohm supplied the propulsion module. NASA's Ames Research Center managed the atmospheric probe, which was built by Hughes Aircraft Company . At launch,

15576-512: Was an American robotic space probe that studied the planet Jupiter and its moons , as well as the asteroids Gaspra and Ida . Named after the Italian astronomer Galileo Galilei , it consisted of an orbiter and an entry probe. It was delivered into Earth orbit on October 18, 1989, by Space Shuttle Atlantis , during STS-34 . Galileo arrived at Jupiter on December 7, 1995, after gravitational assist flybys of Venus and Earth, and became

15708-507: Was built by Hughes Aircraft Company 's Space and Communications Group at its El Segundo, California plant. It weighed 339 kilograms (747 lb) and was 86 centimeters (34 in) high. Inside the probe's heat shield , the scientific instruments were protected from extreme heat and pressure during its high-speed journey into the Jovian atmosphere, entering at 48 kilometers per second (110,000 mph). Temperatures reached around 16,000 °C (29,000 °F). The ablative heat shield

15840-455: Was built up around a single 1802 microprocessor and 32K of RAM (for HLMs) or 16K of RAM (for LLMs). Two HLMs and two LLMs resided on the spun side while two LLMs were on the despun side. Thus, total memory capacity available to the CDH subsystem was 176K of RAM: 144K allocated to the spun side and 32K to the despun side. Each HLM was responsible for the following functions: Each LLM was responsible for

15972-404: Was composed of the same functional elements, consisting of multiplexers (MUX), high-level modules (HLM), low-level modules (LLM), power converters (PC), bulk memory (BUM), data management subsystem bulk memory (DBUM), timing chains (TC), phase locked loops (PLL), Golay coders (GC), hardware command decoders (HCD) and critical controllers (CRC). The CDH subsystem was responsible for maintaining

16104-416: Was designed to measure the numbers and energies of ions and electrons whose energies exceeded about 20 keV (3.2 fJ). The EPD could also measure the direction of travel of such particles and, in the case of ions, could determine their composition (whether the ion is oxygen or sulfur , for example). The EPD used silicon solid-state detectors and a time-of-flight detector system to measure changes in

16236-405: Was determined to very likely be an expanding debris cloud from a collision of asteroids rather than a planet. Similarly, Proxima Centauri c has been observed to be far brighter than expected for its low mass of 7 Earth masses, which may be attributed to a ring system of about 5 R J . A 56-day-long sequence of dimming events in the star V1400 Centauri observed in 2007 was interpreted as

16368-439: Was determined with reference to the Sun and Canopus , which were monitored with two primary and four secondary sensors. There was also an inertial reference unit and an accelerometer . This allowed it to take high-resolution images, but the functionality came at a cost of increased weight. A Mariner weighed 722 kilograms (1,592 lb) compared to just 146 kilograms (322 lb) for a Pioneer. John R. Casani , who had headed

16500-483: Was developed and built by Messerschmitt-Bölkow-Blohm and provided by West Germany, the major international partner in Project Galileo . At the time, solar panels were not practical at Jupiter's distance from the Sun; the spacecraft would have needed a minimum of 65 square meters (700 sq ft) of panels. Chemical batteries would likewise be prohibitively large due to technological limitations. The solution

16632-520: Was made of carbon phenolic . NASA built a special laboratory, the Giant Planet Facility, to simulate the heat load, which was similar to the convective and radiative heating experienced by an ICBM warhead reentering the atmosphere. The probe's electronics were powered by 13 lithium sulfur dioxide batteries manufactured by Honeywell 's Power Sources Center in Horsham, Pennsylvania . Each cell

16764-406: Was obtained by New Horizons spacecraft. The previous upper limit, obtained from HST and Cassini observations, was near 4 km. 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. The age of the main ring

16896-433: Was the size of a D battery so existing manufacturing tools could be used. They provided a nominal power output of about 7.2-ampere hours capacity at a minimal voltage of 28.05 volts. The probe included seven instruments for taking data on its plunge into Jupiter: In addition, the probe's heat shield contained instrumentation to measure ablation during descent. Lacking the fuel to escape Jupiter's gravity well, at

17028-408: Was to use a Mariner program spacecraft like that used for Voyager for the Jupiter orbiter, rather than a Pioneer. Pioneer was stabilized by spinning the spacecraft at 60 rpm , which gave a 360-degree view of the surroundings, and did not require an attitude control system. By contrast, Mariner had an attitude control system with three gyroscopes and two sets of six nitrogen jet thrusters. Attitude

17160-417: Was two radioisotope thermoelectric generators (RTGs) which powered the spacecraft through the radioactive decay of plutonium-238 . The heat emitted by this decay was converted into electricity through the solid-state Seebeck effect . This provided a reliable and long-lasting source of electricity unaffected by the cold environment and high-radiation fields in the Jovian system. Each GPHS-RTG , mounted on

17292-440: Was used to separate natural magnetic fields from engineering-induced fields. Another source of potential error in measurement came from the bending and twisting of the long magnetometer boom. To account for these motions, a calibration coil was mounted rigidly on the spacecraft to generate a reference magnetic field during calibrations. The magnetic field at the surface of the Earth has a strength of about 50,000  nT . At Jupiter,

17424-605: Was written in the HAL/S programming language, which was also used in the Space Shuttle program . Memory capacity provided by each BUM was 16K of RAM , while the DBUMs each provided 8K of RAM. There were two BUMs and two DBUMs in the CDH subsystem and they all resided on the spun side of the spacecraft. The BUMs and DBUMs provided storage for sequences and contain various buffers for telemetry data and interbus communication. Every HLM and LLM

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