3 Juno

Template:Short description {{#invoke:other uses|otheruses}} {{#invoke:infobox|infoboxTemplate | class = vcard | titleclass = fn org | title = 3 Juno | image = {{#invoke:InfoboxImage|InfoboxImage|image=3 Juno VLT (2021).png|upright={{#if:||1.1}}|alt=}} | caption = | headerstyle = {{#if:#D6D6D6|background-color:#D6D6D6|background-color:#E0CCFF}} | labelstyle = max-width:{{#if:||11em}}; | autoheaders = y

| header1 = Discovery

| header10 = {{#if:|Designations|Designations}}

| header20 = Orbital characteristics{{#ifeq:|yes| (barycentric)}}<ref name="jpldata" />

| data21 = | data22 = {{#if:13 September 2023
(JD 2453300.5) |Epoch 13 September 2023
(JD 2453300.5)}} | data23 = {{#if: | Uncertainty parameter {{{uncertainty}}}}} | label24 = Observation arc | data24 = | label25 = Earliest precovery date | data25 = | label26 = {{#switch:{{{apsis}}} |apsis|gee|barion|center|centre|(apsis)=Apo{{{apsis}}} |Ap{{#if:|{{{apsis}}}|helion}}}} | data26 = Template:Convert | label27 = Peri{{#if:|{{{apsis}}}|helion}} | data27 = Template:Convert | label28 = Peri{{#if:|{{{apsis}}}|apsis}} | data28 = | label29 = {{#switch:{{{apsis}}} |helion|astron=Ap{{{apsis}}} |Apo{{#if:|{{{apsis}}}|apsis}}}} | data29 = | label30 = Periastron | data30 = | label31 = Apoastron | data31 = | label32 = Template:Longitem | data32 = Template:Convert | label33 = Template:Longitem | data33 = | label34 = Eccentricity | data34 = 0.2562 | label35 = Template:Longitem | data35 = 4.361 yr | label36 = Template:Longitem | data36 = | label37 = Template:Longitem | data37 = 17.93 km/s | label38 = Template:Longitem | data38 = Template:Val | label39 = Template:Longitem | data39 = | label40 = Inclination | data40 = 12.991° | label41 = Template:Longitem | data41 = | label42 = Template:Longitem | data42 = 169.84° | label43 = Template:Longitem | data43 = | label44 = Template:Longitem | data44 = 2 April 2023 | label45 = Template:Longitem | data45 = 247.74° | label46 = Template:Nowrap | data46 = | label47 = Satellite of | data47 = | label48 = Group | data48 = | label49 = {{#switch: |yes|true=Satellites |Known satellites}} | data49 = | label50 = Star | data50 = | label51 = Earth MOID | data51 = Template:Convert | label52 = Mercury MOID | data52 = | label53 = Venus MOID | data53 = | label54 = Mars MOID | data54 = | label55 = Jupiter MOID | data55 = | label56 = Saturn MOID | data56 = | label57 = Uranus MOID | data57 = | label58 = Neptune MOID | data58 = | label59 = T_Jupiter | data59 =

| header60 = Proper orbital elements<ref name="Juno-POE">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

| label61 = Template:Longitem | data61 = {{#if:2.6693661 |2.6693661 AU}} | label62 = Template:Longitem | data62 = 0.2335060 | label63 = Template:Longitem | data63 = 13.2515192° | label64 = Template:Longitem | data64 = {{#if:82.528181 |82.528181 deg Template:\yr}} | label65 = Template:Longitem | data65 = {{#if:82.528181|{{#expr:360/82.528181 round 5}} yr
({{#expr:365.25*360/82.528181 round 3}} d) }} | label66 = Template:Longitem | data66 = {{#if:43.635655|43.635655 arcsec Template:\yr }} | label67 = Template:Longitem | data67 = {{#if:−61.222138|−61.222138 arcsec Template:\yr}}

| header70 = Template:Anchor{{#if:yes| Physical characteristics|Physical characteristics}}

| label71 = Dimensions | data71 = (288 × 250 × 225) ± 5 km<ref name=VLT/>
(320 × 267 × 200) ± 6 km<ref name="Baer"> {{#invoke:citation/CS1|citation |CitationClass=web }} </ref> | label72 = Template:Longitem | data72 = Template:Val<ref name=VLT>P. Vernazza et al. (2021) VLT/SPHERE imaging survey of the largest main-belt asteroids: Final results and synthesis. Astronomy & Astrophysics 54, A56</ref>
Template:Val<ref name="jpldata"/> | label73 = Template:Longitem | data73 = | label74 = Template:Longitem | data74 = | label75 = Template:Longitem | data75 = | label76 = Flattening | data76 = | label77 = Circumference | data77 = | label78 = Template:Longitem | data78 = | label79 = Volume | data79 = | label80 = Mass | data80 = Template:Val Template:Efn<ref name=VLT/>
Template:Val<ref name="Baer2011">James Baer, Steven Chesley & Robert Matson (2011) "Astrometric masses of 26 asteroids and observations on asteroid porosity." The Astronomical Journal, Volume 141, Number 5</ref>Template:Refn | label81 = Template:Longitem | data81 = Template:Val<ref name=VLT/>
Template:Val<ref name="Baer2011"/> | label82 = Template:Longitem | data82 = Template:Cvt | label83 = Template:Longitem | data83 = | label84 = Template:Longitem | data84 = Template:V2 km/s | label85 = Template:Longitem | data85 = 7.21 hr<ref name="jpldata"/> (0.3004 d)<ref name="lc">

{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref> | label86 = Template:Longitem | data86 = | label87 = Template:Longitem | data87 = 31.75 m/sTemplate:Efn | label88 = Template:Longitem | data88 = | label89 = Template:Longitem | data89 = | label90 = Template:Longitem | data90 = | label91 = Template:Longitem | data91 = 27° ± 5°<ref name="kaasalainen2002"/> | label92 = Template:Longitem | data92 = 103° ± 5°<ref name="kaasalainen2002"/> | label93 = {{#if:yes |Template:Longitem |Albedo}} | data93 = 0.202<ref name=VLT/>
0.238<ref name="jpldata"/><ref name="iras" /> | label94 = Temperature | data94 = ~163 K
max: 301 K (+28°C)<ref name="lim2005">

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| data100 = {{#if:|

Surface temp.	min	mean	max
{{{temp_name1}}}
{{{temp_name2}}}
{{{temp_name3}}}
{{{temp_name4}}}

}}

| label101 = Surface absorbed dose rate | data101 = | label102 = Surface equivalent dose rate | data102 = | label103 = Template:Longitem | data103 = S<ref name="jpldata"/><ref name="tax">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> | label104 = Template:Longitem | data104 = | label105 = Template:Longitem | data105 = 7.4<ref name="AstDys-Juno">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="bright2005">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> to 11.55 | label106 = Template:Longitem | data106 = 5.33<ref name="jpldata"/><ref name="iras">

{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref> | label107 = Template:Longitem | data107 = 0.30" to 0.07"

| header110 = Atmosphere

| below = {{#if:||Template:Reflist }}

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Juno (minor-planet designation: 3 Juno) is a large asteroid in the asteroid belt. Juno was the third asteroid discovered, in 1804, by German astronomer Karl Harding.<ref>Template:Citation</ref> It is tied with three other asteroids as the thirteenth largest asteroid, and it is one of the two largest stony (S-type) asteroids, along with 15 Eunomia. (Ceres is the largest asteroid.) It is estimated to contain 1% of the total mass of the asteroid belt.<ref name="Pitjeva05">

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HistoryEdit

DiscoveryEdit

Juno was discovered on 1 September 1804, by Karl Ludwig Harding.<ref>Template:Cite book</ref> 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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Name and symbolEdit

Juno is named after the mythological Juno, the highest Roman goddess. The adjectival form is Junonian (from Latin jūnōnius), with the historical final n of the name (still seen in the French form, Junon) reappearing, analogous to Pluto ~ Plutonian.<ref name=OED/> 'Juno' is the international name for the asteroid, subject to local variation: Italian Giunone, French Junon, Russian Юнона (Yunona), etc.<ref group="lower-alpha">There are two exceptions: 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).</ref>

The old astronomical symbol of Juno, still used in astrology, is a scepter topped by a star, Template:Angbr. There were many graphic variants with a more elaborated scepter, such as orbed symbol of Juno, sometimes tilted at an angle to provide more room for decoration. The generic asteroid symbol of a disk with its discovery number, Template:Angbr, was introduced in 1852 and quickly became the norm.<ref name="Forbes1971">Template:Cite journal</ref><ref>Template:Cite journal</ref> The scepter symbol was resurrected for astrological use in 1973.<ref>Eleanor Bach (1973) Ephemerides of the asteroids: Ceres, Pallas, Juno, Vesta, 1900–2000. Celestial Communications.</ref>

CharacteristicsEdit

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.; Precise determination of the motion of planets and some astronomical constants from modern observations Template:Webarchive, 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.<ref name="Baer"/> The orbital period of Juno is 4.36578 years.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</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 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<ref name="brightestasteroids">

{{#invoke:citation/CS1|citation

|CitationClass=web }} </ref>—only just visible with binoculars—and at smaller elongations a Template:Convert telescope will be required to resolve it.<ref name="telescope">

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|CitationClass=web }} (archived) </ref> It is the main body in the Juno family.

Juno was originally considered a planet, along with 1 Ceres, 2 Pallas, and 4 Vesta.<ref name="Hilton"/> In 1811, Schröter estimated Juno to be as large as 2290 km in diameter.<ref name="Hilton">

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|CitationClass=web }} </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

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 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.<ref name="ecc">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Juno rotates in a prograde direction with an axial tilt of approximately 50°.<ref name="kaasalainen2002">The north pole points towards ecliptic coordinates (β, λ) = (27°, 103°) within a 5° uncertainty.

Template:Cite journal</ref> The maximum temperature on the surface, directly facing the Sun, was measured at about 293 K on 2 October 2001. Taking into account the heliocentric distance at the time, this gives an estimated maximum temperature of 301 K (+28 °C) at perihelion.<ref name="lim2005"/>

File:Juno orbit 2018.png

The orbit of Juno is significantly elliptical with a small inclination, moving between Mars and Jupiter

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.<ref name="gaffey1993">

Template:Cite journal </ref> Infrared images reveal that Juno possesses an approximately 100 km-wide crater or ejecta feature, the result of a geologically young impact.<ref name="harvard-pr0318">

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|CitationClass=web }} </ref><ref name="baliunas2003">Template:Cite journal</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">Template:Cite journal</ref>

ObservationsEdit

Juno was the first asteroid for which an occultation was observed. It passed in front of a dim star (SAO 112328) on 19 February 1958. Since then, several occultations by Juno have been observed, the most fruitful being the occultation of SAO 115946 on 11 December 1979, which was registered by 18 observers.<ref name="millis1981">Template:Cite journal</ref> Juno occulted the magnitude 11.3 star PPMX 9823370 on 29 July 2013,<ref>Asteroid Occultation Updates – 29 Jul 2013</ref> and 2UCAC 30446947 on 30 July 2013.<ref>Asteroid Occultation Updates – 30 Jul 2013.</ref>

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.<ref name="Pitjeva04">

Template:Cite conference</ref> 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.<ref name="usno1999">Template:Cite journal</ref>

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.<ref name="baliunas2003"/>

Juno 4 wavelengths.jpg

Juno seen at four wavelengths with a large crater in the dark (Hooker telescope, 2003
Juno mpl anim.gif

Juno moving across background stars
3Juno-LB1-apmag.jpg

Juno during opposition in 2009
Animation of the asteroid Juno as imaged by ALMA.webm

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

OppositionsEdit

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 oppositions were on 1 December 2005, at a distance of 1.063 AU, magnitude 7.55, and on 17 November 2018, at a minimum distance of 1.036 AU, magnitude 7.45.<ref>The Astronomical Almanac for the year 2018, G14</ref><ref>Asteroid 3 Juno at opposition Template:Webarchive 16 Nov 2018 at 11:31 UTC</ref> The next favorable opposition will be 30 October 2031, at a distance of 1.044 AU, magnitude 7.42.