694 Ekard

694 Ekard
	A three-dimensional model of 694 Ekard based on its light curve
Discovery
Discovered by	Joel Hastings Metcalf
Discovery site	Taunton, Massachusetts
Discovery date	7 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 arc	106.44 yr (38878 d)
Aphelion	3.5372 AU (529.16 Gm)
Perihelion	1.8114 AU (270.98 Gm)
Semi-major axis	2.6743 AU (400.07 Gm)
Eccentricity	0.32265
Orbital period	4.37 yr (1597.4 d)
Mean anomaly	201.11°
Mean motion	0° 13m 31.332s / day
Inclination	15.849°
Longitude of ascending node	230.116°
Argument of perihelion	111.400°
Physical characteristics
Mean radius	45.39±2 km[1]; 45.39 km[2]
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]

694 Ekard is a minor planet orbiting the Sun that was discovered by American astronomer Joel Hastings Metcalf on November 7, 1909.

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

Yeomans, Donald K., "694 Ekard", JPL Small-Body Database Browser, NASA Jet Propulsion Laboratory, retrieved 7 May 2016.
Delbo', Marco; Tanga, Paolo (February 2009), "Thermal inertia of main belt asteroids smaller than 100 km from IRAS data", Planetary and Space Science, 57 (2), pp. 259–265, arXiv:0808.0869, Bibcode:2009P&SS...57..259D, doi:10.1016/j.pss.2008.06.015.
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, 62, pp. 512–517, Bibcode:1985Icar...62..512Z, doi:10.1016/0019-1035(85)90191-5.
Ostro, S. J.; et al. (August 1985), "Mainbelt asteroids - Dual-polarization radar observations", Science, 229 (4712), pp. 442–446, Bibcode:1985Sci...229..442O, doi:10.1126/science.229.4712.442, PMID 17738665.
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.

External links

694 Ekard at AstDyS-2, Asteroids—Dynamic Site
- Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
694 Ekard at the JPL Small-Body Database
- Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters

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[JPL-1] Yeomans, Donald K., "694 Ekard", JPL Small-Body Database Browser, NASA Jet Propulsion Laboratory, retrieved 7 May 2016.

[Delbo2009-2] Delbo', Marco; Tanga, Paolo (February 2009), "Thermal inertia of main belt asteroids smaller than 100 km from IRAS data", Planetary and Space Science, 57 (2), pp. 259–265, arXiv:0808.0869, Bibcode:2009P&SS...57..259D, doi:10.1016/j.pss.2008.06.015.

[Zeigler1985-3] 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, 62, pp. 512–517, Bibcode:1985Icar...62..512Z, doi:10.1016/0019-1035(85)90191-5.

[Ostro1985-4] Ostro, S. J.; et al. (August 1985), "Mainbelt asteroids - Dual-polarization radar observations", Science, 229 (4712), pp. 442–446, Bibcode:1985Sci...229..442O, doi:10.1126/science.229.4712.442, PMID 17738665.

[Timerson2010-5] 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.