139 Juewa

139 Juewa (/dʒuˈeɪwɑː/ joo-AY-wah) is a very large and dark main belt asteroid. It is probably composed of primitive carbonaceous material. It was the first asteroid discovered from China.

DiscoveredbyJames Craig Watson

Discoverydate10 October 1874

MPCdesignation

(139) Juewa

PronunciationEnglish: /dʒuˈeɪwɑː/ joo-AY-wah
Mandarin: [ɻwêɪxwǎ]

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139 Juewa

Discovery
Discovered by	James Craig Watson
Discovery date	10 October 1874
Designations
MPC designation	(139) Juewa
Pronunciation	English: /dʒuˈeɪwɑː/ joo-AY-wah Mandarin: [ɻwêɪxwǎ]
Alternative designations	A874 TA
Minor planet category	Main belt
Orbital characteristics[1]
Epoch 31 July 2016 (JD 2457600.5)
Uncertainty parameter 0
Observation arc	121.07 yr (44222 d)
Aphelion	3.26884 AU (489.012 Gm)
Perihelion	2.29261 AU (342.970 Gm)
Semi-major axis	2.78073 AU (415.991 Gm)
Eccentricity	0.17553
Orbital period (sidereal)	4.64 yr (1693.7 d)
Mean anomaly	60.2817°
Mean motion	0° 12m 45.187s / day
Inclination	10.9127°
Longitude of ascending node	1.83417°
Argument of perihelion	165.566°
Physical characteristics
Dimensions	148.3±4.3 km × 142.3±15.6 km
Mean diameter	151.116±1.596 km[1] 161.43±7.38 km[2]
Mass	(5.54±2.20)×1018 kg[2] (3.262 ± 0.778/0.933)×1018 kg[3]
Mean density	2.51±1.05 g/cm3[2] 1.805 ± 0.430/0.516 g/cm3[3]
Equatorial surface gravity	0.0438 m/s²
Equatorial escape velocity	0.0828 km/s
Synodic rotation period	20.991 h (0.8746 d)
Geometric albedo	0.052±0.015[1] 0.0444±0.0164[4]
Temperature	~167 K
Spectral type	CP (Tholen)[4]
Absolute magnitude (H)	8.06,[1] 7.924[4]

Close

Juewa was discovered from Beijing by the visiting American astronomer James Craig Watson on 10 October 1874; Watson was in China to observe the transit of Venus. Watson asked Prince Gong to name the asteroid. Gong's choice was 瑞華星 (roughly, "Star of China's fortune"). Watson used the first two characters ('star' being redundant), transliterating them Juewa in Wade convention of the time. (In pinyin, 瑞華 is transliterated ruìhuá.)^[5]

Since 1988 there have been 8 reported stellar occultations by Juewa. From the occultation on 31 August 2013 the best fit ellipse measures 148.3±4.3 km × 142.3±15.6 km.^[6]

13-cm radar observations of this asteroid from the Arecibo Observatory between 1980 and 1985 were used to produce a diameter estimate of 172 km.^[7] Based upon radar data, the near surface solid density of the asteroid is 1.5±0.5 g/cm³.^[8]