JUNO was the third of the minor planets to be discovered on 01st September 1804 being found by Karl Harding at Lilienthal, now in northern Germany. She is the noble queen of the whole Olympian pantheon of gods, whose main responsibilities were in regarded as the sanctity of marriage, and towards the protection of women, especially during childbirth. The Ancient Greeks knew her as Hera, whose name translates as ‘lady’, but in Roman mythology she is both wife and sister of Jupiter (Zeus).
JUNO DATADiscoverer : Karl Ludwig Harding Date : 01 September 1804 Satellites : 0 Diameter : 290×240×120 km. Polar Tilt : 50 ° ? Period (P) : 4.36 yr. Synodic Period : 447.83 d. Orbital Velocity : 17.93 km.s-1 Perihelion (q) : 1.979 A.U. Aphelion (Q) : 3.358 A.U. Eccentricity (e) : 0.2583 Inclination (i) : 12.971° Mass : 3.0 ×1019 kg. Mean Density : 3.0 g.cm-3 Mean Distance : 2.668 AU or 399.2 ×108 km Sidereal Rotation : 05 hr. 20.5 m. Mean Sidereal Rotation : 0.3004 d. Maximum Diameter : 0.29″ (arcsec) Minimum Diameter : 0.07″ (arcsec) Maximum Magnitude : 7.5 Minimum Magnitude : 10.0 Class : S-type |
Juno takes 4.36 years to orbit the Sun at the mean distance of 2.666 A.U. This is slightly closer in mean distance than either Ceres or Pallas by 0.06AU. Juno is the dimmest of the four main asteroids, reaching the possible maximum of 7.4 magnitude at opposition. As such, it is the smallest body of the four main minor planets, having the mean diameter of 233.9 across. or 290×240×190 km. Orbital eccentricity ‘e’ is 0.2588, and is this similar to Pallas’ orbit. The body is inclined at -13.0° to the ecliptic, finding the range of declinations as anywhere between +13.5° or -13.5°. Like many of the brighter asteroids, the location of Juno can sometimes lie beyond the typical zodiacal constellations on the ecliptic, but in the case of Juno, the orbit lies closer to the current aequator of the sky. This means the variation in declination is less than Ceres or Pallas.
Juno’s brightness can be significantly different between successive oppositions, which can be attributed to the eccentric orbit . During favourable oppositions (2005, 2009 and 2018) the maximum magnitude can reach 7.5, while during poorer apparitions (2008, 2012, 2016 and 2021) the magnitude reaches only 10th magnitude. During best oppositions, Juno may have a distance just over 1 A.U. or 151 million kilometres, or receed as far as about 2.4 A.U. or 362 million km. Telecopically the asteroid’s disk remains only star-like, whose maximum diameter subtends just 0.29 arc seconds.
Juno, like Vesta, has been shown to be slightly variable in brightness. Johann Schöeter was first to notice this in 1810 and had assumed that the changes were the rotation period. His 27-hour long period proved to be too long (Juno has a period of 7.2 hours) but this showed that these bodies planets were not round but either oval or irregular in shape. Another possibility is such light-variations are caused by different surface features causing variation in albedos - the measure of the way light is reflected by substances on the surface of asteroidal bodies. This latter point was difficult to prove, as most minor planets appear as pin-points of light and do not show discernible disks.
The photometric observations of Juno have shown variations of only about 0.15 magnitudes, whose oscillations suggest the rotation period of 7.209 hours. There are also slight colour changes in the measured B-V of around 0.03 magnitudes, which likely show differences on the surface by a number of features - though nothing in extent when compared with Vesta.
********************************************************* 0h UT (J2000) Mag Δ r El. Con DATE R.A. Decl. V A.U. A.U. o hh mm.m o ′ ********************************************************* 12 Jan 16 43.8 -12 05 11.5 4.033 3.355 041 Oph 26 Jan 17 00.8 -12 04 11.5 3.885 3.353 051 Oph 09 Feb 17 16.5 -11 49 11.5 3.713 3.349 061 Oph 23 Feb 17 30.4 -11 19 11.4 3.523 3.344 072 Ser 08 Mar 17 42.1 -10 37 11.3 3.320 3.338 082 Ser 22 Mar 17 51.1 -09 45 11.1 3.111 3.331 094 Oph 05 Apr 17 56.8 -08 44 11.0 2.906 3.322 106 Oph 19 Apr 17 58.7 -07 39 10.8 2.713 3.312 118 Oph 03 May 17 56.5 -06 34 10.6 2.544 3.300 132 Oph 17 May 17 50.2 -05 37 10.4 2.409 3.287 145 Oph 31 May 17 40.5 -04 54 10.2 2.319 3.273 156 Oph 14 Jun 17 28.7 -04 32 10.1 2.280 3.258 161 Oph 28 Jun 17 16.9 -04 35 10.1 2.294 3.241 154 Oph 12 Jul 17 07.0 -05 04 10.3 2.359 3.223 142 Oph 26 Jul 17 00.4 -05 53 10.5 2.466 3.204 129 Oph 09 Aug 16 57.9 -06 56 10.6 2.605 3.184 116 Oph 23 Aug 16 59.7 -08 08 10.8 2.764 3.162 104 Oph 06 Sep 17 05.4 -09 22 10.9 2.933 3.139 092 Oph 20 Sep 17 14.6 -10 34 11.0 3.103 3.115 081 Oph 04 Oct 17 26.9 -11 39 11.1 3.268 3.090 071 Ser 18 Oct 17 41.7 -12 36 11.1 3.419 3.064 061 Ser 01 Nov 17 58.7 -13 21 11.2 3.554 3.036 051 Ser 15 Nov 18 17.4 -13 53 11.1 3.666 3.007 042 Ser 29 Nov 18 37.6 -14 10 11.1 3.754 2.978 033 Sct 13 Dec 18 58.8 -14 11 11.0 3.814 2.947 025 Sct 27 Dec 19 20.9 -13 57 10.9 3.846 2.915 016 Sgr *********************************************************
********************************************************* 0h UT (J2000) Mag Δ r El. Con DATE R.A. Decl. V A.U. A.U. o hh mm.m o ′ ********************************************************* 10 Jan 19 43.5 -13 25 10.8 3.848 2.882 010 Sgr 24 Jan 20 06.3 -12 39 10.8 3.820 2.849 008 Sgr 07 Feb 20 29.2 -11 38 10.8 3.763 2.814 014 Cap 21 Feb 20 52.0 -10 23 10.8 3.678 2.779 021 Aqr 07 Mar 21 14.6 -08 58 10.8 3.568 2.742 029 Aqr 21 Mar 21 36.7 -07 24 10.8 3.434 2.706 037 Aqr 04 Apr 21 58.3 -05 44 10.7 3.279 2.668 045 Aqr 18 Apr 22 19.3 -04 01 10.6 3.107 2.630 053 Aqr 02 May 22 39.4 -02 17 10.5 2.919 2.592 061 Aqr 16 May 22 58.7 +00 37 10.4 2.721 2.553 070 Psc 30 May 23 16.8 +00 56 10.2 2.515 2.514 078 Psc 13 Jun 23 33.3 +02 16 10.0 2.305 2.476 087 Psc 27 Jun 23 48.0 +03 19 09.8 2.096 2.437 097 Psc 11 Jul 00 00.3 +03 55 09.5 1.892 2.398 107 Psc 25 Jul 00 09.3 +03 59 09.2 1.700 2.360 118 Psc 08 Aug 00 14.2 +03 20 08.9 1.528 2.322 131 Psc 22 Aug 00 14.5 +01 51 08.5 1.382 2.286 145 Psc 05 Sep 00 09.9 +00 27 08.1 1.275 2.250 160 Psc 19 Sep 00 01.6 -03 21 07.7 1.213 2.216 176 Psc 03 Oct 23 52.1 -06 21 07.8 1.201 2.183 165 Aqr 17 Oct 23 44.5 -08 51 08.1 1.237 2.151 149 Aqr 31 Oct 23 41.6 -10 27 08.4 1.314 2.122 133 Aqr 14 Nov 23 44.3 -11 03 08.6 1.419 2.095 120 Aqr 28 Nov 23 52.7 -10 45 08.8 1.543 2.071 108 Aqr 12 Dec 00 06.1 -09 42 09.0 1.677 2.049 097 Cet 26 Dec 00 23.4 -08 03 09.2 1.814 2.031 088 Cet *********************************************************
********************************************************* 0h UT (J2000) Mag Δ r El. Con DATE R.A. Decl. V A.U. A.U. o hh mm.m o ′ ********************************************************* 09 Jan 00 43.9 -05 59 09.3 1.952 2.015 079 Cet 23 Jan 01 06.9 -03 37 09.4 2.087 2.004 071 Cet 06 Feb 01 31.9 -01 03 09.5 2.216 1.995 064 Cet 20 Feb 01 58.6 +01 34 09.6 2.340 1.990 057 Cet 06 Mar 02 26.7 +04 10 09.7 2.456 1.989 051 Cet 20 Mar 02 56.0 +06 39 09.7 2.566 1.992 045 Cet 03 Apr 03 26.4 +08 55 09.7 2.668 1.998 039 Tau 17 Apr 03 57.7 +10 54 09.8 2.762 2.008 034 Tau 01 May 04 29.7 +12 32 09.8 2.849 2.022 029 Tau 15 May 05 02.1 +13 47 09.8 2.927 2.039 023 Ori 29 May 05 34.7 +14 36 09.8 2.995 2.059 018 Ori 12 Jun 06 07.2 +14 60 09.7 3.054 2.082 014 Ori 26 Jun 06 39.4 +14 57 09.7 3.102 2.107 010 Gem 10 Jul 07 10.9 +14 31 09.7 3.137 2.135 008 Gem 24 Jul 07 41.6 +13 42 09.8 3.159 2.165 010 Gem 07 Aug 08 11.3 +12 35 09.9 3.166 2.197 014 Cnc 21 Aug 08 39.9 +11 11 10.0 3.157 2.231 020 Cnc 04 Sep 09 07.2 +09 35 10.1 3.130 2.266 026 Cnc 18 Sep 09 33.2 +07 50 10.2 3.085 2.302 033 Leo 02 Oct 09 57.7 +06 00 10.3 3.021 2.339 040 Sex 16 Oct 10 20.7 +04 10 10.3 2.937 2.377 047 Sex 30 Oct 10 42.1 +02 24 10.3 2.834 2.415 056 Sex 13 Nov 11 01.5 +00 45 10.3 2.714 2.454 064 Leo 27 Nov 11 18.7 +00 41 10.2 2.579 2.493 074 Leo 11 Dec 11 33.2 -01 48 10.2 2.432 2.531 084 Leo 25 Dec 11 44.4 -02 32 10.0 2.280 2.570 096 Vir *********************************************************
********************************************************* 0h UT (J2000) Mag Δ r El. Con DATE R.A. Decl. V A.U. A.U. o hh mm.m o ′ ********************************************************* 08 Jan 11 51.8 -02 44 09.9 2.130 2.609 108 Vir 22 Jan 11 54.5 -02 20 09.7 1.992 2.647 122 Vir 05 Feb 11 52.4 -01 16 09.5 1.878 2.684 137 Vir 19 Feb 11 45.6 +00 28 09.3 1.801 2.722 153 Vir 05 Mar 11 35.4 +02 38 09.0 1.775 2.758 171 Leo 19 Mar 11 24.2 +04 54 09.1 1.805 2.794 172 Leo 02 Apr 11 14.5 +06 54 09.4 1.892 2.829 155 Leo 16 Apr 11 08.1 +08 22 09.8 2.028 2.863 139 Leo 30 Apr 11 06.1 +09 14 10.1 2.203 2.896 125 Leo 14 May 11 08.2 +09 30 10.3 2.403 2.928 111 Leo 28 May 11 14.1 +09 16 10.6 2.619 2.960 099 Leo 11 Jun 11 23.1 +08 38 10.8 2.841 2.990 088 Leo 25 Jun 11 34.5 +07 40 10.9 3.062 3.019 078 Leo 09 Jul 11 47.7 +06 28 11.1 3.275 3.047 068 Vir 23 Jul 12 02.4 +05 05 11.2 3.474 3.074 059 Vir 06 Aug 12 18.2 +03 35 11.3 3.657 3.100 050 Vir 20 Aug 12 34.9 +01 59 11.3 3.819 3.124 041 Vir 03 Sep 12 52.3 +00 20 11.3 3.956 3.148 032 Vir 17 Sep 13 10.2 -01 18 11.3 4.066 3.170 024 Vir 01 Oct 13 28.5 -02 55 11.3 4.146 3.191 015 Vir 15 Oct 13 47.1 -04 27 11.2 4.195 3.211 008 Vir 29 Oct 14 05.9 -05 53 11.2 4.211 3.229 008 Vir 12 Nov 14 24.7 -07 10 11.3 4.194 3.246 015 Vir 26 Nov 14 43.3 -08 18 11.4 4.144 3.262 023 Vir 10 Dec 15 01.6 -09 13 11.4 4.062 3.277 033 Lib 24 Dec 15 19.2 -09 55 11.5 3.949 3.290 042 Lib *********************************************************
********************************************************* 0h UT (J2000) Mag Δ r El. Con DATE R.A. Decl. V A.U. A.U. o hh mm.m o ′ ********************************************************* 07 Jan 15 35.8 -10 21 11.5 3.809 3.303 052 Lib 21 Jan 15 51.2 -10 32 11.4 3.645 3.313 063 Lib 04 Feb 16 04.7 -10 26 11.3 3.463 3.323 074 Sco 18 Feb 16 16.0 -10 03 11.2 3.270 3.331 085 Sco 03 Mar 16 24.3 -09 23 11.1 3.072 3.338 097 Oph 17 Mar 16 29.3 -08 28 11.0 2.880 3.344 109 Oph 31 Mar 16 30.3 -07 20 10.8 2.703 3.348 122 Oph 14 Apr 16 27.1 -06 04 10.6 2.555 3.351 136 Oph 28 Apr 16 20.1 -04 46 10.4 2.445 3.353 150 Oph 12 May 16 10.0 -03 37 10.2 2.384 3.353 161 Ser 26 May 15 58.5 -02 45 10.2 2.377 3.352 161 Ser 09 Jun 15 47.5 -02 18 10.3 2.424 3.350 151 Ser 23 Jun 15 38.7 -02 18 10.5 2.520 3.346 138 Ser 07 Jul 15 33.3 -02 45 10.7 2.656 3.341 125 Ser 21 Jul 15 31.8 -03 32 10.9 2.819 3.335 112 Ser 04 Aug 15 34.0 -04 34 11.1 2.999 3.328 100 Lib 18 Aug 15 39.7 -05 45 11.2 3.186 3.319 089 Lib 01 Sep 15 48.5 -07 01 11.3 3.371 3.309 078 Lib 15 Sep 15 59.9 -08 18 11.4 3.548 3.297 068 Lib 29 Sep 16 13.5 -09 32 11.4 3.709 3.284 058 Sco 13 Oct 16 28.9 -10 40 11.4 3.851 3.270 048 Oph 27 Oct 16 46.0 -11 39 11.4 3.969 3.255 039 Oph 10 Nov 17 04.3 -12 29 11.4 4.060 3.239 030 Oph 24 Nov 17 23.6 -13 07 11.3 4.120 3.221 021 Ser 08 Dec 17 43.7 -13 31 11.3 4.150 3.202 014 Ser 22 Dec 18 04.2 -13 41 11.2 4.146 3.181 010 Ser *********************************************************
********************************************************* 0h UT (J2000) Mag Δ r El. Con DATE R.A. Decl. V A.U. A.U. o hh mm.m o ′ ********************************************************* 05 Jan 18 25.0 -13 37 11.2 4.110 3.160 013 Sct 19 Jan 18 45.8 -13 18 11.2 4.042 3.137 020 Sct 02 Feb 19 06.3 -12 46 11.3 3.943 3.113 028 Sgr 16 Feb 19 26.2 -12 00 11.2 3.816 3.088 037 Sgr 02 Mar 19 45.3 -11 03 11.2 3.663 3.062 046 Aql 16 Mar 20 03.4 -09 57 11.1 3.487 3.034 055 Aql 30 Mar 20 20.0 -08 43 11.0 3.294 3.005 065 Cap 13 Apr 20 35.0 -07 25 10.9 3.086 2.976 074 Aql 27 Apr 20 47.9 -06 07 10.8 2.869 2.945 084 Aqr 11 May 20 58.3 -04 53 10.6 2.650 2.913 095 Aqr 25 May 21 05.6 -03 48 10.4 2.434 2.881 106 Aqr 08 Jun 21 09.3 -02 59 10.1 2.229 2.847 118 Aqr 22 Jun 21 08.9 -02 34 09.8 2.044 2.812 131 Aqr 06 Jul 21 04.0 -02 39 09.5 1.888 2.777 144 Aqr 20 Jul 20 55.2 -03 21 09.2 1.773 2.741 158 Aqr 03 Aug 20 43.8 -04 40 09.0 1.706 2.704 167 Aqr 17 Aug 20 32.0 -06 25 09.0 1.691 2.667 160 Aql 31 Aug 20 22.5 -08 22 09.2 1.727 2.629 147 Aql 14 Sep 20 17.4 -10 13 09.4 1.806 2.591 132 Cap 28 Sep 20 17.5 -11 48 09.6 1.916 2.552 119 Cap 12 Oct 20 23.0 -12 59 09.8 2.048 2.513 106 Cap 26 Oct 20 33.3 -13 44 09.9 2.190 2.474 094 Cap 09 Nov 20 47.8 -14 01 10.0 2.334 2.435 084 Aqr 23 Nov 21 05.6 -13 52 10.1 2.475 2.397 074 Aqr 07 Dec 21 26.1 -13 18 10.1 2.606 2.359 065 Aqr 21 Dec 21 48.7 -12 19 10.2 2.725 2.321 056 Cap *********************************************************
********************************************************* 0h UT (J2000) Mag Δ r El. Con DATE R.A. Decl. V A.U. A.U. o hh mm.m o ′ ********************************************************* 04 Jan 22 12.8 -10 60 10.1 2.828 2.284 048 Aqr 18 Jan 22 38.2 -09 20 10.1 2.914 2.249 040 Aqr 01 Feb 23 04.6 -07 25 10.1 2.983 2.214 032 Aqr 15 Feb 23 31.7 -05 17 10.0 3.033 2.181 025 Aqr 01 Mar 23 59.6 -02 60 09.9 3.066 2.150 019 Psc 15 Mar 00 28.2 +00 37 09.8 3.082 2.121 012 Cet 29 Mar 00 57.4 +01 48 09.6 3.082 2.094 007 Cet 12 Apr 01 27.2 +04 10 09.6 3.067 2.070 005 Psc 26 Apr 01 57.8 +06 25 09.6 3.040 2.048 008 Psc 10 May 02 29.1 +08 29 09.6 3.001 2.030 013 Cet 24 May 03 01.0 +10 18 09.7 2.952 2.014 018 Cet 07 Jun 03 33.4 +11 48 09.7 2.893 2.002 023 Tau 21 Jun 04 06.2 +12 56 09.7 2.827 1.994 029 Tau 05 Jul 04 39.1 +13 39 09.7 2.753 1.989 034 Tau 19 Jul 05 11.9 +13 55 09.7 2.673 1.989 039 Ori 02 Aug 05 44.1 +13 45 09.7 2.585 1.991 044 Tau 16 Aug 06 15.4 +13 09 09.7 2.491 1.998 050 Ori 30 Aug 06 45.3 +12 08 09.7 2.390 2.008 056 Gem 13 Sep 07 13.5 +10 48 09.6 2.282 2.022 062 CMi 27 Sep 07 39.6 +09 11 09.5 2.167 2.039 069 CMi 11 Oct 08 03.0 +07 23 09.5 2.046 2.059 077 CMi 25 Oct 08 23.3 +05 31 09.4 1.920 2.082 085 Hya 08 Nov 08 39.8 +03 43 09.2 1.792 2.107 094 Hya 22 Nov 08 51.9 +02 08 09.1 1.665 2.135 104 Hya 06 Dec 08 58.6 +00 56 08.9 1.546 2.166 116 Hya 20 Dec 08 59.5 +00 22 08.7 1.442 2.198 129 Hya *********************************************************
************************ Opposition Conjunction ************************ 10 Apr 2007 02 Sep 2006 12 Jun 2008 14 Nov 2007 21 Sep 2009 18 Jan 2009 13 Mar 2011 10 Jul 2010 20 May 2012 23 Oct 2011 04 Aug 2013 13 Apr 2014 01 Feb 2015 28 Sep 2015 28 Apr 2016 30 Nov 2016 03 Jul 2017 16 Feb 2018 22 Nov 2018 25 Aug 2019 04 Apr 2020 09 Nov 2020 *************************
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