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[[Image:Moon and Asteroids 1 to 10 at 10 km per px.png|thumb|left|Size comparison: the first 10 asteroids profiled against Earth's [[Moon]]. Juno is third from the left.]]<!-- [[Image:3AS.jpg|Artist's concept of 3 Juno|thumb|left]] --> |
[[Image:Moon and Asteroids 1 to 10 at 10 km per px.png|thumb|left|Size comparison: the first 10 asteroids profiled against Earth's [[Moon]]. Juno is third from the left.]]<!-- [[Image:3AS.jpg|Artist's concept of 3 Juno|thumb|left]] --> |
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Juno is one of the largest asteroids, containing approximately 1.0% the mass of the entire asteroid belt. In a ranking by size, it is tenth. It vies with [[15 Eunomia]] for the honour of being the largest of the stony [[S-type asteroid]]s, although the newest estimates put Juno in second place. |
Juno is one of the largest asteroids, containing approximately 1.0% the mass of the entire asteroid belt. In a ranking by size, it is tenth. It vies with [[15 Eunomia]] for the honour of being the largest of the stony [[S-type asteroid]]s, although the newest estimates put Juno in second place. |
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It is the main body in the [[Juno family]]. |
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Amongst S-types it is unusually reflective, which may be indicative of different surface properties. This high reflectivity explains its relatively high [[apparent magnitude|magnitude]] for a small object not near the inner edge of the asteroid belt. Juno can reach +7.5 at a favourable opposition, which is brighter than [[Neptune]] or [[Titan (moon)|Titan]], and explains it discovery predating the larger asteroids [[10 Hygiea|Hygiea]], [[52 Europa|Europa]], [[511 Davida|Davida]] and [[704 Interamnia|Interamnia]]. At most oppositions, however, Juno reaches around +9.0 - only just visible with [[binoculars]] - and at smaller [[elongation]]s a 3-inch [[telescope]] will be required to resolve it. It is the main body in the [[Juno family]]. |
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Juno was originally considered a planet, along with [[1 Ceres]], [[2 Pallas]], and [[4 Vesta]]. It was re-classified as an asteroid, with the other three, when many more additional asteroids were discovered. Juno's small size and irregular shape preclude it from being considered a [[dwarf planet]] under the [[2006 redefinition of planet|IAU classification]]. |
Juno was originally considered a planet, along with [[1 Ceres]], [[2 Pallas]], and [[4 Vesta]]. It was re-classified as an asteroid, with the other three, when many more additional asteroids were discovered. Juno's small size and irregular shape preclude it from being considered a [[dwarf planet]] under the [[2006 redefinition of planet|IAU classification]]. |
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Juno orbits at a slightly closer mean distance to the [[Sun]] than Ceres or Pallas. Its orbit is moderately inclined at around 12° to the [[ecliptic]], but has an eccentricity higher than that of [[Pluto]]. This high eccentricity brings Juno closer to the Sun at [[perihelion]] than Vesta and further out at [[aphelion]] than Ceres. Juno had the most eccentric orbit of any known body until [[33 Polyhymnia|Polyhymnia]] was discovered in 1854, and of asteroids over 200km in diameter only [[324 Bamberga]] has a more eccentric orbit. |
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Juno rotates in a [[prograde and retrograde motion|prograde]] direction, with the north pole pointing towards [[ecliptic coordinate system|ecliptic coordinates]] (β, λ) = (27°, 103°) with a 10° uncertainty.<ref name="kaasalainen2002">{{cite journal | last= Kaasalainen | first= M. | authorlink= | coauthors= J. Torppa; J. Piironen | title= Models of Twenty Asteroids from Photometric Data | journal= Icarus | volume= 159 | issue= 2 | pages= 369–395 | date= 2002 | publisher= | url= http://www.rni.helsinki.fi/~mjk/IcarPIII.pdf | format= [[PDF]] | doi= 10.1006/icar.2002.6907}}</ref> This gives an [[axial tilt]] of 51°. |
Juno rotates in a [[prograde and retrograde motion|prograde]] direction, with the north pole pointing towards [[ecliptic coordinate system|ecliptic coordinates]] (β, λ) = (27°, 103°) with a 10° uncertainty.<ref name="kaasalainen2002">{{cite journal | last= Kaasalainen | first= M. | authorlink= | coauthors= J. Torppa; J. Piironen | title= Models of Twenty Asteroids from Photometric Data | journal= Icarus | volume= 159 | issue= 2 | pages= 369–395 | date= 2002 | publisher= | url= http://www.rni.helsinki.fi/~mjk/IcarPIII.pdf | format= [[PDF]] | doi= 10.1006/icar.2002.6907}}</ref> This gives an [[axial tilt]] of 51°. |
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Spectroscopic studies of the Junonian surface permit the conclusion that Juno could be the body of origin of ordinary [[chondrite]]s, a common group of stony meteorites composed of iron-containing [[silicate]]s such as [[olivine]] and [[pyroxene]].<ref name="gaffey1993">{{cite journal | last= Gaffey | first= Michael J. | authorlink= | coauthors= Burbine, Thomas H.; Piatek, Jennifer L.; Reed, Kevin L.; Chaky, Damon A.; Bell, Jeffrey F.; Brown, R. H. | title= Mineralogical variations within the S-type asteroid class | journal= Icarus | year= 1993 | volume= 106 | issue= 2 | pages= 573 | url= http://adsabs.harvard.edu/abs/1993Icar..106..573G | doi= 10.1006/icar.1993.1194}}</ref> The maximum temperature on the surface, when the sun is overhead, was measured at about 293 [[Kelvin|K]] on [[October 2]], [[2001]]. Taking into account also the [[heliocentric]] distance at the time, this gives an estimated maximum of 301 K (+28°[[Celsius|C]]) at |
Spectroscopic studies of the Junonian surface permit the conclusion that Juno could be the body of origin of ordinary [[chondrite]]s, a common group of stony meteorites composed of iron-containing [[silicate]]s such as [[olivine]] and [[pyroxene]].<ref name="gaffey1993">{{cite journal | last= Gaffey | first= Michael J. | authorlink= | coauthors= Burbine, Thomas H.; Piatek, Jennifer L.; Reed, Kevin L.; Chaky, Damon A.; Bell, Jeffrey F.; Brown, R. H. | title= Mineralogical variations within the S-type asteroid class | journal= Icarus | year= 1993 | volume= 106 | issue= 2 | pages= 573 | url= http://adsabs.harvard.edu/abs/1993Icar..106..573G | doi= 10.1006/icar.1993.1194}}</ref> The maximum temperature on the surface, when the sun is overhead, was measured at about 293 [[Kelvin|K]] on [[October 2]], [[2001]]. Taking into account also the [[heliocentric]] distance at the time, this gives an estimated maximum of 301 K (+28°[[Celsius|C]]) at perihelion.<ref name="lim2005" /> |
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Infrared images reveal that it possesses an approximately 100 km wide crater or ejecta feature, the result of a geologically young impact.<ref name="harvard-pr0318">{{cite web | last= | first= | authorlink= | coauthors= | title= Asteroid Juno Has A Bite Out Of It | work= | publisher= Harvard-Smithsonian Center for Astrophysics | date= 2003-08-06| url= http://cfa-www.harvard.edu/press/pr0318.html | format= | doi= | accessdate= 2007-02-18}}</ref><ref name="baliunas2003">{{cite journal | last= Baliunas | first= Sallie | authorlink= | coauthors= Donahue, Robert; Rampino, Michael R.; Gaffey, Michael J.; Shelton, J. Christopher; Mohanty, Subhanjoy | title= Multispectral analysis of asteroid 3 Juno taken with the 100-inch telescope at Mount Wilson Observatory | journal= Icarus | year= 2003 | volume= 163 | issue= 1 | pages= 135-141 | url= http://pubs.giss.nasa.gov/docs/2003/2003_Baliunas_etal.pdf | format= [[PDF]] | doi= 10.1016/S0019-1035(03)00049-6}}</ref> |
Infrared images reveal that it possesses an approximately 100 km wide crater or ejecta feature, the result of a geologically young impact.<ref name="harvard-pr0318">{{cite web | last= | first= | authorlink= | coauthors= | title= Asteroid Juno Has A Bite Out Of It | work= | publisher= Harvard-Smithsonian Center for Astrophysics | date= 2003-08-06| url= http://cfa-www.harvard.edu/press/pr0318.html | format= | doi= | accessdate= 2007-02-18}}</ref><ref name="baliunas2003">{{cite journal | last= Baliunas | first= Sallie | authorlink= | coauthors= Donahue, Robert; Rampino, Michael R.; Gaffey, Michael J.; Shelton, J. Christopher; Mohanty, Subhanjoy | title= Multispectral analysis of asteroid 3 Juno taken with the 100-inch telescope at Mount Wilson Observatory | journal= Icarus | year= 2003 | volume= 163 | issue= 1 | pages= 135-141 | url= http://pubs.giss.nasa.gov/docs/2003/2003_Baliunas_etal.pdf | format= [[PDF]] | doi= 10.1016/S0019-1035(03)00049-6}}</ref> |
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Revision as of 11:09, 5 July 2007
 Juno moving among background stars | |
| Discovery | |
|---|---|
| Discovered by | Karl Ludwig Harding |
| Discovery date | September 1, 1804 |
| Designations | |
| none | |
| Main belt (Juno clump) | |
| Symbol |  |
| Orbital characteristics | |
| Epoch November 25, 2005 (JD 2453699.5) | |
| Aphelion | 502.276 Gm (3.358 AU) |
| Perihelion | 296.03 Gm (1.979 AU) |
| 399.155 Gm (2.668 AU) | |
| Eccentricity | 0.2583 |
| 1591.93 d (4.36 a) | |
Average orbital speed | 17.93 km/s |
| 7.879° | |
| Inclination | 12.971° |
| 170.125° | |
| 247.839° | |
| Physical characteristics | |
| Dimensions | 290×240×190 km |
| Mass | 3.0×1019 kg[1][2] |
Mean density | 3.4 g/cm³ |
| 0.12 m/s² | |
| 0.18 km/s | |
| 0.3004 d[3] | |
| Albedo | 0.238[4] |
| Temperature | ~163 K max: 301 K (+28° C)[5] |
Spectral type | S-type asteroid[6] |
| 5.33[4] | |
Juno (IPA: [ˈdʒunoʊ]), designated 3 Juno in the Minor Planet Center catalogue system, was the third asteroid to be discovered and is one of the largest main belt asteroids, being the second heaviest of the stony S-type. It was discovered on September 1, 1804 by German astronomer Karl L. Harding and named after the mythological figure Juno, the highest Roman goddess. The adjectival form of the name is Junonian.
Characteristics
Juno is one of the largest asteroids, containing approximately 1.0% the mass of the entire asteroid belt. In a ranking by size, it is tenth. It vies with 15 Eunomia for the honour of being the largest of the stony S-type asteroids, although the newest estimates put Juno in second place.
Amongst S-types it is unusually reflective, which may be indicative of different surface properties. This high reflectivity explains its relatively high magnitude for a small object not near the inner edge of the asteroid belt. Juno can reach +7.5 at a favourable opposition, which is brighter than Neptune or Titan, and explains it discovery predating the larger asteroids Hygiea, Europa, Davida and Interamnia. At most oppositions, however, Juno reaches around +9.0 - only just visible with binoculars - and at smaller elongations a 3-inch telescope will be required to resolve it. It is the main body in the Juno family.
Juno was originally considered a planet, along with 1 Ceres, 2 Pallas, and 4 Vesta. It was re-classified as an asteroid, with the other three, when many more additional asteroids were discovered. Juno's small size and irregular shape preclude it from being considered a dwarf planet under the IAU classification.
Juno orbits at a slightly closer mean distance to the Sun than Ceres or Pallas. Its orbit is moderately inclined at around 12° to the ecliptic, but has an eccentricity higher than that of Pluto. This high eccentricity brings Juno closer to the Sun at perihelion than Vesta and further out at aphelion than Ceres. Juno had the most eccentric orbit of any known body until Polyhymnia was discovered in 1854, and of asteroids over 200km in diameter only 324 Bamberga has a more eccentric orbit.
Juno rotates in a prograde direction, with the north pole pointing towards ecliptic coordinates (β, λ) = (27°, 103°) with a 10° uncertainty.[7] This gives an axial tilt of 51°.
Spectroscopic studies of the Junonian surface permit the conclusion that Juno could be the body of origin of ordinary chondrites, a common group of stony meteorites composed of iron-containing silicates such as olivine and pyroxene.[8] The maximum temperature on the surface, when the sun is overhead, was measured at about 293 K on October 2, 2001. Taking into account also the heliocentric distance at the time, this gives an estimated maximum of 301 K (+28°C) at perihelion.[5]
Infrared images reveal that it possesses an approximately 100 km wide crater or ejecta feature, the result of a geologically young impact.[9][10]
Observations
Some notable observation milestones for Juno include:
- Juno was the first asteroid for which an occultation was observed. It passed in front of a dim star (SAO 112328) on February 19, 1958. Since then, several occultations by Juno have been observed, the most fruitful being on December 11, 1979 which was registered by 18 observers.[11]
- Radio signals from spacecraft in orbit around Mars and/or on its surface have been used to estimate the mass of Juno from the tiny perturbations induced by it onto the motion of Mars.[2]
- A study by James Hilton suggests that Juno's orbit changed (slightly) around 1839, "very likely" due to perturbations from a passing asteroid, whose identity has not been determined yet. An alternate yet unlikely explanation is an impact by a sizeable body.[12]
- In 1996, Juno was imaged by the Hooker Telescope at Mount Wilson Observatory at visible and near-IR wavelengths, using adaptive optics. The images spanned a whole rotation period and revealed an irregular (lumpy) shape with a dark feature, interpreted as a fresh impact site.[10]
References
- Yeomans, Donald K. "Horizons system". NASA JPL. Retrieved 2007-03-20. — Horizons can be used to obtain a current ephemeris
- ^ Pitjeva, E. V. (2005). "High-Precision Ephemerides of Planets—EPM and Determination of Some Astronomical Constants" (PDF). Solar System Research. 39 (3): 176. doi:10.1007/s11208-005-0033-2.
- ^ a b Pitjeva, E. V. (2004). "Estimations of masses of the largest asteroids and the main asteroid belt from ranging to planets, Mars orbiters and landers". 35th COSPAR Scientific Assembly. Held 18 - 25 July 2004, in Paris, France. p. 2014.
{{cite conference}}: Unknown parameter|booktitle=ignored (|book-title=suggested) (help) - ^ Harris, A. W. (2006). "Asteroid Lightcurve Derived Data. EAR-A-5-DDR-DERIVED-LIGHTCURVE-V8.0". NASA Planetary Data System. Retrieved 2007-03-15.
{{cite web}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ a b Davis, D. R. (2002). "Asteroid Albedos. EAR-A-5-DDR-ALBEDOS-V1.1". NASA Planetary Data System. Retrieved 2007-02-18.
{{cite web}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ a b Lim, Lucy F. (2005). "Thermal infrared (8-13μm) spectra of 29 asteroids: the Cornell Mid-Infrared Asteroid Spectroscopy (MIDAS) Survey". Icarus. 173 (2): 385–408. doi:10.1016/j.icarus.2004.08.005.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ Neese, C. (2005). "Asteroid Taxonomy.EAR-A-5-DDR-TAXONOMY-V5.0". NASA Planetary Data System. Retrieved 2007-03-15.
{{cite web}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ Kaasalainen, M. (2002). "Models of Twenty Asteroids from Photometric Data" (PDF). Icarus. 159 (2): 369–395. doi:10.1006/icar.2002.6907.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ Gaffey, Michael J. (1993). "Mineralogical variations within the S-type asteroid class". Icarus. 106 (2): 573. doi:10.1006/icar.1993.1194.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ "Asteroid Juno Has A Bite Out Of It". Harvard-Smithsonian Center for Astrophysics. 2003-08-06. Retrieved 2007-02-18.
{{cite web}}: Cite has empty unknown parameter:|coauthors=(help) - ^ a b Baliunas, Sallie (2003). "Multispectral analysis of asteroid 3 Juno taken with the 100-inch telescope at Mount Wilson Observatory" (PDF). Icarus. 163 (1): 135–141. doi:10.1016/S0019-1035(03)00049-6.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ Millis, R. L. (1981). "The diameter of Juno from its occultation of AG+0°1022". Astronomical Journal. 86: 306–313. doi:10.1086/112889.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help); Unknown parameter|month=ignored (help) - ^ Hilton, James L. (1999). "US Naval Observatory Ephemerides of the Largest Asteroids". Astronomical Journal. 117: 1077–1086. doi:10.1086/300728.
{{cite journal}}: Unknown parameter|month=ignored (help)
External links
Wikimedia Commons has media related to 3 Juno.
- Well resolved images from four angles taken at Mount Wilson observatory
- NASA Planetary Data System asteroid data sets
- Shape model deduced from light curve