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3 Juno

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3 Juno Juno symbol.svg
Juno orbit 2018.png
The orbit of Juno is significantly elliptical with a small inclination, moving between Mars and Jupiter.
Discovery
Discovered byKarl Ludwig Harding
Discovery dateSeptember 1, 1804
Designations
MPC designation(3) Juno
Pronunciation/ˈn/
Named after
Juno (Latin: Iūno)
none
Main belt (Juno clump)
AdjectivesJunonian /ˈnniən/[1]
Orbital characteristics[2]
Epoch JD 2457000.5 (9 December 2014)
Aphelion3.35293 AU
Perihelion1.98847 AU
2.67070 AU
Eccentricity0.25545
4.36463 yr
17.93 km/s
33.077°
Inclination12.9817°
169.8712°
248.4100°
Proper orbital elements[3]
2.6693661 AU
0.2335060
13.2515192°
82.528181 deg / yr
4.36215 yr
(1593.274 d)
Precession of perihelion
43.635655 arcsec / yr
Precession of the ascending node
−61.222138 arcsec / yr
Physical characteristics
Dimensions(320×267×200)±6 km[4]
Mean diameter
233 km[2]
216 000 km2[5]
Volume8 950 000 km3[5]
Mass2.67 ×1019 kg[4]
Mean density
3.20±0.56 g/cm3[4]
Equatorial surface gravity
0.12 m/s2
Equatorial escape velocity
0.18 km/s
7.21 hr[2] (0.3004 d)[6]
Equatorial rotation velocity
31.75 m/s[5]
0.238[2][7]
Temperature~163 K
max: 301 K (+28°C)[8]
S[2][9]
7.4[10][11] to 11.55
5.33[2][7]
0.30" to 0.07"


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Juno, minor-planet designation 3 Juno in the Minor Planet Center catalogue system, is an asteroid in the asteroid belt. Juno was the third asteroid discovered, in 1804, by German astronomer Karl Harding. It is the 11th-largest asteroid, and one of the two largest stony (S-type) asteroids, along with 15 Eunomia. It is estimated to contain 1% of the total mass of the asteroid belt.[12]

History[edit]

Discovery[edit]

Juno was discovered on 1 September 1804, by Karl Ludwig Harding.[2] It was the third asteroid found, but was initially considered to be a planet; it was reclassified as an asteroid and minor planet during the 1850s.[13]

Name[edit]

Juno is named after the mythological Juno, the highest Roman goddess. The adjectival form is Junonian (jūnōnius).

With two exceptions, 'Juno' is the international name, subject to local variation: Italian Giunone, French Junon, Russian Yunona, etc.[lower-alpha 1] Its planetary symbol is ③. An older symbol, still occasionally seen, is ⚵ (Old symbol of Juno).

Characteristics[edit]

Juno is one of the larger asteroids, perhaps tenth by size and containing approximately 1% the mass of the entire asteroid belt.[14] It is the second-most-massive S-type asteroid after 15 Eunomia.[4] Even so, Juno has only 3% the mass of Ceres.[4]

Size comparison: the first 10 asteroids discovered, profiled against Earth's Moon. Juno is third from the left.

The orbital period of Juno is 4.36578 years.[15]

Amongst S-type asteroids, Juno is unusually reflective, which may be indicative of distinct surface properties. This high albedo explains its relatively high apparent 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 is the reason for it being discovered before the larger asteroids Hygiea, Europa, Davida, and Interamnia. At most oppositions, however, Juno only reaches a magnitude of around +8.7[16]—only just visible with binoculars—and at smaller elongations a 3-inch (76 mm) telescope will be required to resolve it.[17] It is the main body in the Juno family.

Planets 1807–1845
1 Mercury☿
2 Venus♀
3 Earth ⊕
4 Mars♂
5 Vesta Vesta symbol.svg
6 Juno Juno symbol.svg
7 Ceres Ceres symbol.svg
8 Pallas Pallas symbol.svg
9 Jupiter♃
10 Saturn ♄
11 Uranus♅

Juno was originally considered a planet, along with 1 Ceres, 2 Pallas, and 4 Vesta.[18] In 1811, Schröter estimated Juno to be as large as 2290 km in diameter.[18] All four were reclassified as asteroids as additional asteroids were discovered. Juno's small size and irregular shape preclude it from being designated a dwarf planet.

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 extreme eccentricity, greater 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 was discovered in 1854, and of asteroids over 200 km in diameter only 324 Bamberga has a more eccentric orbit.[19]

Juno rotates in a prograde direction with an axial tilt of approximately 50°.[20] The maximum temperature on the surface, directly facing the Sun, was measured at about 293 K on October 2, 2001. Taking into account the heliocentric distance at the time, this gives an estimated maximum temperature of 301 K (+28 °C) at perihelion.[8]

Spectroscopic studies of the Junonian surface permit the conclusion that Juno could be the progenitor of chondrites, a common type of stony meteorite composed of iron-bearing silicates such as olivine and pyroxene.[21] Infrared images reveal that Juno possesses an approximately 100 km-wide crater or ejecta feature, the result of a geologically young impact.[22][23]

Observations[edit]

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 the occultation of SAO 115946 on December 11, 1979, which was registered by 18 observers.[24] Juno occulted the magnitude 11.3 star PPMX 9823370 on July 29, 2013,[25] and 2UCAC 30446947 on July 30, 2013.[26]

Radio signals from spacecraft in orbit around Mars and on its surface have been used to estimate the mass of Juno from the tiny perturbations induced by it onto the motion of Mars.[27] Juno's orbit appears to have changed slightly around 1839, very likely due to perturbations from a passing asteroid, whose identity has not been determined.[28]

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 shape and a dark albedo feature, interpreted as a fresh impact site.[23]

Juno 4 wavelengths.jpg
Juno seen at four wavelengths with a large crater in the dark (Hooker telescope, 2003)
Animation
Juno mpl anim.gif
Juno moving across background stars
Star field
3Juno-LB1-apmag.jpg
Juno during opposition in 2009
ALMA

Video of Juno taken as part of ALMA's Long Baseline Campaign

Oppositions[edit]

Juno reaches opposition from the Sun every 15.5 months or so, with its minimum distance varying greatly depending on whether it is near perihelion or aphelion. Sequences of favorable oppositions occur every 10th opposition, i.e. just over every 13 years. The last favorable opposition was on December 1, 2005 at a distance of 1.063 AU, magnitude 7.55, and its next favorable one is November 17, 2018 at a minimum distance of 1.036 AU, magnitude 7.45.[29][30] The opposition after that will be October 30, 2031, at a distance of 1.044 AU, magnitude 7.42.

See also[edit]

Notes[edit]

  1. The exceptions are Greek, where the name was translated to its Hellenic equivalent, Hera (3 Ήρα), as in the cases of 1 Ceres and 4 Vesta; and Chinese, where it is called the 'marriage-god(dess) star' (婚神星 hūnshénxīng). This contrasts with the goddess Juno, for which Chinese uses the transliterated Latin name (朱諾 zhūnuò).

References[edit]

  1. Junonian (3rd ed.), Oxford University Press, September 2005, http://oed.com/search?searchType=dictionary&q=Junonian (Subscription or UK public library membership required.)
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
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  5. 5.0 5.1 5.2 Calculated based on the known parameters
  6. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  7. 7.0 7.1 Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  8. 8.0 8.1 Lim, Lucy F.; McConnochie, Timothy H.; Bell, James F.; Hayward, Thomas L. (2005). "Thermal infrared (8–13 µm) spectra of 29 asteroids: the Cornell Mid-Infrared Asteroid Spectroscopy (MIDAS) Survey". Icarus 173 (2): 385–408. Bibcode 2005Icar..173..385L. doi:10.1016/j.icarus.2004.08.005.
  9. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  10. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  11. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  12. Pitjeva, E. V. (2005). "High-Precision Ephemerides of Planets—EPM and Determination of Some Astronomical Constants" (PDF). Solar System Research 39 (3): 176. Bibcode 2005SoSyR..39..176P. doi:10.1007/s11208-005-0033-2. Archived from the original on 2008-10-31. https://web.archive.org/web/20081031065523/http://iau-comm4.jpl.nasa.gov/EPM2004.pdf.
  13. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  14. Pitjeva, E. V.; Precise determination of the motion of planets and some astronomical constants from modern observations, in Kurtz, D. W. (Ed.), Proceedings of IAU Colloquium No. 196: Transits of Venus: New Views of the Solar System and Galaxy, 2004
  15. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  16. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
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  18. 18.0 18.1 Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  19. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  20. The north pole points towards ecliptic coordinates (β, λ) = (27°, 103°) within a 10° uncertainty. Kaasalainen, M.; Torppa, J.; Piironen, J. (2002). "Models of Twenty Asteroids from Photometric Data" (PDF). Icarus 159 (2): 369–395. Bibcode 2002Icar..159..369K. doi:10.1006/icar.2002.6907. http://www.rni.helsinki.fi/~mjk/IcarPIII.pdf.
  21. 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. Bibcode 1993Icar..106..573G. doi:10.1006/icar.1993.1194.
  22. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  23. 23.0 23.1 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. Bibcode 2003Icar..163..135B. doi:10.1016/S0019-1035(03)00049-6. https://pubs.giss.nasa.gov/docs/2003/2003_Baliunas_ba04100j.pdf.
  24. Millis, R. L.; Wasserman, L. H.; Bowell, E.; Franz, O. G.; White, N. M.; Lockwood, G. W.; Nye, R.; Bertram, R. et al. (February 1981). "The diameter of Juno from its occultation of AG+0°1022". Astronomical Journal 86: 306–313. Bibcode 1981AJ.....86..306M. doi:10.1086/112889.
  25. Asteroid Occultation Updates – Jul 29, 2013
  26. Asteroid Occultation Updates – Jul 30, 2013.
  27. Lua error in Module:Citation/CS1 at line 637: attempt to concatenate local 'chapter' (a table value).
  28. Hilton, James L. (February 1999). "US Naval Observatory Ephemerides of the Largest Asteroids". Astronomical Journal 117 (2): 1077–1086. Bibcode 1999AJ....117.1077H. doi:10.1086/300728. http://aa.usno.navy.mil/publications/reports/asteroid_ephemerides.html. Retrieved 2012-04-15.
  29. The Astronomical Amanac for the year 2018, G14
  30. Asteroid 3 Juno at opposition 16 Nov 2018 at 11:31 UTC

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External links[edit]

Template:Large asteroids Template:Solar System table

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