Editing 3 Juno (section)

==Characteristics==
Juno is one of the larger asteroids, perhaps tenth by size and containing approximately 1% the mass of the entire [[asteroid belt]].<ref name="Pitjeva04b">Pitjeva, E. V.; [http://journals.cambridge.org/production/action/cjoGetFulltext?fulltextid=303499 ''Precise determination of the motion of planets and some astronomical constants from modern observations''] {{Webarchive|url=https://web.archive.org/web/20231214154827/https://www.cambridge.org/core/redirect-support |date=14 December 2023 }}, in Kurtz, D. W. (Ed.), ''Proceedings of IAU Colloquium No. 196: Transits of Venus: New Views of the Solar System and Galaxy'', 2004</ref> It is the second-most-massive S-type asteroid after 15 Eunomia.<ref name="Baer"/> Even so, Juno has only 3% the mass of [[Ceres (dwarf planet)|Ceres]].<ref name="Baer"/> The orbital period of Juno is 4.36578 years.<ref>{{cite web|title=Comets Asteroids |url=http://comets-asteroids.findthedata.org/l/3015/3-Juno |archive-url=https://archive.today/20140514074257/http://comets-asteroids.findthedata.org/l/3015/3-Juno |url-status=dead |archive-date=14 May 2014 |publisher=Find The Data.org |access-date=14 May 2014 }}</ref>

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#Observation|Neptune]] or [[Exploration of Titan|Titan]], and is the reason for it being discovered before the larger asteroids [[10 Hygiea|Hygiea]], [[52 Europa|Europa]], [[511 Davida|Davida]], and [[704 Interamnia|Interamnia]]. At most oppositions, however, Juno only reaches a magnitude of around +8.7<ref name="brightestasteroids">
 {{cite web
 |title=The Brightest Asteroids 
 |publisher=The Jordanian Astronomical Society 
 |author=Odeh, Moh'd 
 |url=http://jas.org.jo/ast.html 
 |access-date=2008-05-21 
 |archive-url=https://web.archive.org/web/20080511115437/http://www.jas.org.jo/ast.html 
 |archive-date=11 May 2008 
 |url-status=dead 
}}
</ref>—only just visible with [[binoculars]]—and at smaller [[Elongation (astronomy)|elongation]]s a {{convert|3|in|mm|adj=on}} [[telescope]] will be required to resolve it.<ref name="telescope">
 {{cite web|date=2004 |title=What Can I See Through My Scope? |publisher=Ballauer Observatory |url=http://www.allaboutastro.com/Articlepages/whatcanisee.html |access-date=2008-07-20 |url-status=dead |archive-url=https://web.archive.org/web/20110726123615/http://www.allaboutastro.com/Articlepages/whatcanisee.html |archive-date=26 July 2011 }} (archived)
</ref> It is the main body in the [[Juno family]].

Juno was originally considered a planet, along with [[Ceres (dwarf planet)|1 Ceres]], [[2 Pallas]], and [[4 Vesta]].<ref name="Hilton"/> In 1811, [[Johann Hieronymus Schröter|Schröter]] estimated Juno to be as large as 2290&nbsp;km in diameter.<ref name="Hilton">
 {{cite web
  |date=2007-11-16
  |author=Hilton, James L |author-link=James L. Hilton
  |title=When did asteroids become minor planets?
  |work=U.S. Naval Observatory
  |url=http://aa.usno.navy.mil/faq/docs/minorplanets.php
  |access-date=2008-06-22 |archive-url = https://web.archive.org/web/20080324182332/http://aa.usno.navy.mil/faq/docs/minorplanets.php |archive-date = 2008-03-24}} 
</ref> 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]].
[[File:Moon_and_Asteroids_1_to_10.svg|center|thumb|400x400px|Size comparison: the first 10 asteroids discovered, profiled against Earth's [[Moon]]. Juno is third from the left.]]
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 [[orbital eccentricity|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&nbsp;km in diameter only [[324 Bamberga]] has a more eccentric orbit.<ref name="ecc">{{cite web|title=MBA Eccentricity Screen Capture |publisher=JPL Small-Body Database Search Engine |url=http://home.comcast.net/~kpheider/3Juno-ecc.jpg |access-date=2008-11-01 |url-status=dead |archive-url=https://web.archive.org/web/20090327111705/http://home.comcast.net/~kpheider/3Juno-ecc.jpg |archive-date=27 March 2009 }}</ref>

Juno rotates in a [[direct motion|prograde]] direction with an [[axial tilt]] of approximately 50°.<ref name="kaasalainen2002">The north pole points towards [[ecliptic coordinate system|ecliptic coordinates]] (β, λ) = (27°, 103°) within a 5° uncertainty. 
 {{cite journal | last= Kaasalainen | first= M. | author2= Torppa, J. | author3= Piironen, J. | title= Models of Twenty Asteroids from Photometric Data | journal= Icarus | volume= 159 | issue= 2 | pages= 369–395 | date= 2002 | url= http://www.rni.helsinki.fi/~mjk/IcarPIII.pdf | doi= 10.1006/icar.2002.6907 | bibcode= 2002Icar..159..369K | access-date= 30 November 2005 | archive-date= 16 February 2008 | archive-url= https://web.archive.org/web/20080216072340/http://www.rni.helsinki.fi/~mjk/IcarPIII.pdf | url-status= dead }}</ref> The maximum temperature on the surface, directly facing the Sun, was measured at about 293 [[Kelvin|K]] on 2 October 2001. Taking into account the [[heliocentric]] distance at the time, this gives an estimated maximum temperature of 301 K (+28&nbsp;°C) at perihelion.<ref name="lim2005"/>

[[File:Juno orbit 2018.png|thumb|The orbit of Juno is significantly elliptical with a small inclination, moving between Mars and Jupiter|center|400x400px]]Spectroscopic studies of the Junonian surface permit the conclusion that Juno could be the progenitor of [[chondrite]]s, a common type of stony [[meteorite]] composed of iron-bearing [[silicate]]s such as [[olivine]] and [[pyroxene]].<ref name="gaffey1993">
{{cite journal
 | last= Gaffey
 | first= Michael J.
 |author2=Burbine, Thomas H.|author3=Piatek, Jennifer L.|author4=Reed, Kevin L.|author5=Chaky, Damon A.|author6=Bell, Jeffrey F.|author7= Brown, R. H.
 | title= Mineralogical variations within the S-type asteroid class
 | journal= Icarus | date= 1993 | volume= 106 | issue= 2 | page= 573
 | bibcode= 1993Icar..106..573G | doi= 10.1006/icar.1993.1194}}
</ref> [[Infrared]] images reveal that Juno possesses an approximately 100&nbsp;km-wide crater or ejecta feature, the result of a geologically young impact.<ref name="harvard-pr0318">
 {{cite web
 |title=Asteroid Juno Has A Bite Out Of It 
 |publisher=Harvard-Smithsonian Center for Astrophysics 
 |date=2003-08-06 
 |url=http://cfa-www.harvard.edu/press/pr0318.html 
 |access-date=2007-02-18 
 |archive-url=https://web.archive.org/web/20070208013152/http://cfa-www.harvard.edu/press/pr0318.html 
 |archive-date=8 February 2007 
 |url-status=dead 
}}
</ref><ref name="baliunas2003">{{cite journal 
 |last=Baliunas 
 |first=Sallie 
 |author2=Donahue, Robert 
 |author3=Rampino, Michael R. 
 |author4=Gaffey, Michael J. 
 |author5=Shelton, J. Christopher 
 |author6=Mohanty, Subhanjoy 
 |title=Multispectral analysis of asteroid 3 Juno taken with the 100-inch telescope at Mount Wilson Observatory 
 |journal=Icarus 
 |date=2003 
 |volume=163 
 |issue=1 
 |pages=135–141 
 |url=https://pubs.giss.nasa.gov/docs/2003/2003_Baliunas_ba04100j.pdf 
 |doi=10.1016/S0019-1035(03)00049-6 
 |bibcode=2003Icar..163..135B 
 |access-date=18 July 2017 
 |archive-date=23 January 2023 
 |archive-url=https://web.archive.org/web/20230123110931/https://pubs.giss.nasa.gov/docs/2003/2003_Baliunas_ba04100j.pdf 
 |url-status=live 
 }}</ref>

Based on MIDAS infrared data using the [[Hale Telescope]], an average radius of 135.7 ± 11 km was reported in 2004.<ref name="mit.edu">{{cite journal|doi=10.1016/j.icarus.2004.08.005|url=https://www.mit.edu/people/lucylim/2005_Icarus_LimMcConnochie_Thermal_infrared_8-13_micron_spectra.pdf|title=Thermal infrared (8?13 ?m) spectra of 29 asteroids: The Cornell Mid-Infrared Asteroid Spectroscopy (MIDAS) Survey|journal=Icarus|volume=173|issue=2|pages=385|year=2005|last1=Lim|first1=L|last2=McConnochie|first2=T|last3=Belliii|first3=J|last4=Hayward|first4=T|bibcode=2005Icar..173..385L|access-date=26 August 2019|archive-url=https://web.archive.org/web/20160303232808/http://www.mit.edu/people/lucylim/2005_Icarus_LimMcConnochie_Thermal_infrared_8-13_micron_spectra.pdf|archive-date=3 March 2016|url-status=dead}}</ref>