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694 Ekard is a minor planet orbiting the Sun that was discovered by American astronomer Joel Hastings Metcalf on November 7, 1909. The asteroid's name comes from the reverse spelling of Drake University in Des Moines, Iowa, where Seth Barnes Nicholson and his wife calculated its orbit.

694 Ekard
A three-dimensional model of 694 Ekard based on its light curve
Discovery
Discovered byJoel Hastings Metcalf
Discovery siteTaunton, Massachusetts
Discovery date7 November 1909
Designations
MPC designation
(694) Ekard
Alternative designations
1909 JA
Orbital characteristics[1]
Epoch 31 July 2016 (JD 2457600.5)
Uncertainty parameter 0
Observation arc106.44 yr (38878 d)
Aphelion3.5372 AU (529.16 Gm)
Perihelion1.8114 AU (270.98 Gm)
Semi-major axis
2.6743 AU (400.07 Gm)
Eccentricity0.32265
Orbital period (sidereal)
4.37 yr (1597.4 d)
Mean anomaly
201.11°
Mean motion
0° 13m 31.332s / day
Inclination15.849°
Longitude of ascending node
230.116°
Argument of perihelion
111.400°
Physical characteristics
Mean radius
45.39±2 km[1]
45.39 km[2]
Synodic rotation period
5.925 h (0.2469 d)[1][3]
Geometric albedo
0.046[2]
0.0460±0.004[1]
Absolute magnitude (H)
9.17[1][2]

    Photometric observations of this asteroid gave a light curve with a period of 5.925 hours and a brightness variation of 0.50 in magnitude.[3] Measurements of the thermal inertia of 694 Ekard give a value of around 100–140 J m−2 K−1 s−1/2, compared to 50 for lunar regolith and 400 for coarse sand in an atmosphere.[2]

    13-cm radar observations of this asteroid from the Arecibo Observatory between 1980 and 1985 were used to produce a diameter estimate of 101 km.[4] Four separate stellar occultation events involving this asteroid were observed from multiple sites in 2009. The resulting chords matched a least squares equivalent diameter of 90±6 km.[5]


    References


    1. Yeomans, Donald K., "694 Ekard", JPL Small-Body Database Browser, NASA Jet Propulsion Laboratory, retrieved 7 May 2016.
    2. Delbo', Marco; Tanga, Paolo (February 2009), "Thermal inertia of main belt asteroids smaller than 100 km from IRAS data", Planetary and Space Science, vol. 57, no. 2, pp. 259–265, arXiv:0808.0869, Bibcode:2009P&SS...57..259D, doi:10.1016/j.pss.2008.06.015.
    3. Zeigler, K. W.; Florence, W. B. (June 1985), "Photoelectric photometry of asteroids 9 Metis, 18 Melpomene, 60 Echo, 116 Sirona, 230 Athamantis, 694 Ekard, and 1984 KD", Icarus, vol. 62, pp. 512–517, Bibcode:1985Icar...62..512Z, doi:10.1016/0019-1035(85)90191-5.
    4. Ostro, S. J.; et al. (August 1985), "Mainbelt asteroids - Dual-polarization radar observations", Science, vol. 229, no. 4712, pp. 442–446, Bibcode:1985Sci...229..442O, doi:10.1126/science.229.4712.442, PMID 17738665.
    5. Timerson, Brad; Durech, J.; Pilcher, F.; et al. (October 2010), "Occultations by 81 Terpsichore and 694 Ekard in 2009 at Different Rotational Phase Angles", The Minor Planet Bulletin, 37 (4): 140−142, Bibcode:2010MPBu...37..140T.



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    На других языках

    [de] (694) Ekard

    (694) Ekard ist ein Asteroid des Hauptgürtels, der am 7. November 1909 vom US-amerikanischen Astronomen Joel H. Metcalf in Taunton entdeckt wurde.
    - [en] 694 Ekard

    [es] (694) Ekard

    (694) Ekard es un asteroide que forma parte del cinturón de asteroides y fue descubierto por Joel Hastings Metcalf en 1909.

    [ru] (694) Экард

    (694) Экард (англ. Ekard) — астероид главного пояса, который был открыт 7 ноября 1909 года американским астрономом Джоэлом Меткалфом в Тонтонской обсерватории. Назван в честь американского университета Дрейк, записанного в обратном порядке. Тиссеранов параметр относительно Юпитера — 3,253.


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