3 Juno
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 Juno moving among background stars |
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| Discovery | |
|---|---|
| Discovered by: | Karl Ludwig Harding |
| Discovery date: | September 1, 1804 |
| Alternative names: | none |
| Minor planet category: | Main belt (Juno clump) |
| Orbital characteristics | |
| Epoch November 25, 2005 (JD 2453699.5) | |
| Aphelion distance: | 502.276 Gm (3.358 AU) |
| Perihelion distance: | 296.03 Gm (1.979 AU) |
| Semi-major axis: | 399.155 Gm (2.668 AU) |
| Eccentricity: | 0.2583 |
| Orbital period: | 1591.93 d (4.36 a) |
| Avg. orbital speed: | 17.93 km/s |
| Mean anomaly: | 7.879° |
| Inclination: | 12.971° |
| Longitude of ascending node: | 170.125° |
| Argument of perihelion: | 247.839° |
| Physical characteristics | |
| Dimensions: | 290×240×190 km |
| Mass: | 3.0×1019 kg[1][2] |
| Mean density: | 3.4 g/cm³ |
| Equatorial surface gravity: | 0.12 m/s² |
| Escape velocity: | 0.18 km/s |
| Rotation period: | 0.3004 d[3] |
| Albedo: | 0.238[5] |
| Temperature: | ~163 K max: 301 K (+28° C)[6] |
| Spectral type: | S-type asteroid[4] |
| Absolute magnitude: | 5.33[5] |
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.
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[edit] 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 along with Juno's high eccentricity (the highest of any known object until Polyhymnia was discovered in 1854) explains its relatively high magnitude and its discovery predating that of the larger asteroids Hygiea, Europa, Davida and Interamnia. 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 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.[6]
Infrared images reveal that it possesses an approximately 100 km wide crater or ejecta feature, the result of a geologically young impact.[9][10]
[edit] 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]
[edit] References
- Yeomans, Donald K.. Horizons system. NASA JPL. Retrieved on 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: 2014.
- ^ Harris, A. W.; Warner, B.D.; Pravec, P.; Eds. (2006). Asteroid Lightcurve Derived Data. EAR-A-5-DDR-DERIVED-LIGHTCURVE-V8.0.. NASA Planetary Data System. Retrieved on 2007-03-15.
- ^ Neese, C.; Ed. (2005). Asteroid Taxonomy.EAR-A-5-DDR-TAXONOMY-V5.0.. NASA Planetary Data System. Retrieved on 2007-03-15.
- ^ a b Davis, D. R.; Neese, C., Eds. (2002). Asteroid Albedos. EAR-A-5-DDR-ALBEDOS-V1.1.. NASA Planetary Data System. Retrieved on 2007-02-18.
- ^ a b Lim, Lucy F.; McConnochie, Timothy H.; Bell, James F.; Hayward, Thomas L. (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.
- ^ Kaasalainen, M.; J. Torppa; J. Piironen (2002). "Models of Twenty Asteroids from Photometric Data" (PDF). Icarus 159 (2): 369–395. DOI:10.1006/icar.2002.6907.
- ^ Gaffey, Michael J.; Burbine, Thomas H.; Piatek, Jennifer L.; Reed, Kevin L.; Chaky, Damon A.; Bell, Jeffrey F.; Brown, R. H. (1993). "Mineralogical variations within the S-type asteroid class". Icarus 106 (2): 573. DOI:10.1006/icar.1993.1194.
- ^ Asteroid Juno Has A Bite Out Of It. Harvard-Smithsonian Center for Astrophysics (2003-08-06). Retrieved on 2007-02-18.
- ^ a b Baliunas, Sallie; Donahue, Robert; Rampino, Michael R.; Gaffey, Michael J.; Shelton, J. Christopher; Mohanty, Subhanjoy (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.
- ^ Millis, R. L.; Wasserman, L. H.; Bowell, E.; Franz, O. G.; White, N. M.; Lockwood, G. W.; Nye, R.; Bertram, R.; Klemola, A.; Dunham, E.; Morrison, D. (February 1981). "The diameter of Juno from its occultation of AG+0°1022". Astronomical Journal 86: 306-313. DOI:10.1086/112889.
- ^ Hilton, James L. (February 1999). "US Naval Observatory Ephemerides of the Largest Asteroids". Astronomical Journal 117: 1077-1086. DOI:10.1086/300728.
[edit] External links
- Well resolved images from four angles taken at Mount Wilson observatory
- NASA Planetary Data System asteroid data sets
- Shape model deduced from light curve
[edit] See also
| Minor planets | ||
|---|---|---|
| Previous minor planet | 3 Juno | Next minor planet |
| List of asteroids | ||
Vulcanoids · Near-Earth asteroids · Main belt · Jupiter Trojans · Centaurs · Damocloids · Comets · Trans-Neptunians (Kuiper belt • Scattered disc • Oort cloud)
For other objects and regions, see Asteroid groups and families, Binary asteroids, Asteroid moons and the Solar System.
For a complete listing, see List of asteroids. See also Pronunciation of asteroid names and Meanings of asteroid names.
