16974 Iphthime

Hubble Space Telescope image of Iphthime taken in 2013
Discovery[1]
Discovered by	LINEAR
Discovery site	Lincoln Lab's ETS
Discovery date	18 November 1998
Designations
MPC designation	(16974) Iphthime
Pronunciation	/ɪfˈθaɪmiː/[2]
Named after	Iphthime Iphthīmē/Ἰφθῑμη[1] (Greek mythology)
Alternative designations	1998 WR21 · 1974 WX 1986 WS
Minor planet category	Jupiter trojan[1][3] Greek[4] · background[5]
Adjectives	Iphthimean
Orbital characteristics[3]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc	42.86 yr (15,655 d)
Aphelion	5.5556 AU
Perihelion	4.8248 AU
Semi-major axis	5.1902 AU
Eccentricity	0.0704
Orbital period (sidereal)	11.82 yr (4,319 d)
Mean anomaly	261.74°
Mean motion	0° 5m 0.24s / day
Inclination	15.036°
Longitude of ascending node	241.56°
Argument of perihelion	134.72°
Jupiter MOID	0.0605 AU
TJupiter	2.9270
Physical characteristics
Mean diameter	55.43±4.0 km[6] 57.15±3.85 km[7] 57.34±0.33 km[8]
Synodic rotation period	78.9±0.4 h[9]
Geometric albedo	0.065±0.010[8] 0.066±0.009[7] 0.0691±0.011[6]
Spectral type	C (assumed)[10] V–I = 0.960±0.035[10]
Absolute magnitude (H)	9.80[1][3][6][7][8]

16974 Iphthime (/ɪfˈθaɪmiː/; provisional designation 1998 WR₂₁) is a Jupiter trojan and a binary system from the Greek camp, approximately 57 kilometers (35 miles) in diameter. It was discovered on 18 November 1998, by astronomers with the Lincoln Near-Earth Asteroid Research at the ETS Test Site in Socorro, New Mexico.^[1] The dark Jovian asteroid belongs to the 80 largest Jupiter trojans and has a notably slow rotation of 78.9 hours.^[10] It was named after Iphthime from Greek mythology.^[1] The discovery of its companion by Hubble Space Telescope was announced in March 2016.

Orbit and classification

Iphthime is a dark Jovian asteroid orbiting in the leading Greek camp at Jupiter's L₄ Lagrangian point, 60° ahead of its orbit in a 1:1 resonance (see Trojans in astronomy).^[4] It is also a non-family asteroid in the Jovian background population.^[5]

It orbits the Sun at a distance of 4.8–5.6 AU once every 11 years and 10 months (4,319 days; semi-major axis of 5.19 AU). Its orbit has an eccentricity of 0.07 and an inclination of 15° with respect to the ecliptic.^[3] The body's observation arc begins with its first observation as 1974 WX at Crimea-Nauchnij in November 1974, or 24 years prior to its official discovery observation at Socorro.^[1]

Naming

This minor planet was named from Greek mythology after Iphthime, sister of Penelope and daughter of Icarius. Iphthime appears in her sister's dream to comfort her as she is grieving. The official naming citation was published by the Minor Planet Center on 3 December 2017 (M.P.C. 107739).^[11]

Physical characteristics

Iphthime is an assumed C-type asteroid.^[10] Its V–I color index of 0.96 is typical for D-type asteroids, the most common spectral type among the larger Jupiter trojans.^[10]

Rotation period

Iphthime and its companion imaged by the Hubble Space Telescope in 2018

In October 2009, a rotational lightcurve of Iphthime was obtained for the first time by Stefano Mottola from photometric observations during seven nights at the Calar Alto Observatory in Spain. Lightcurve analysis gave a long rotation period of 78.9±0.4 hours or 3.3 days with a brightness amplitude of 0.25 magnitude (U=2+).^[10][9]

References

External links

• (16974) Iphthime, Asteroids with Satellites Database, Johnston's Archive
• Lightcurve Database Query (LCDB), at www.minorplanet.info
• Dictionary of Minor Planet Names, Google books
• Discovery Circumstances: Numbered Minor Planets (15001)-(20000) – Minor Planet Center
• Asteroid 16974 Iphthime at the Small Bodies Data Ferret
• 16974 Iphthime at AstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 16974 Iphthime at the JPL Small-Body Database