 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 | |
| (694) Ekard | |
| 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) |
| 2.6743 AU (400.07 Gm) | |
| Eccentricity | 0.32265 |
| 4.37 yr (1597.4 d) | |
| 201.11° | |
| 0° 13m 31.332s / day | |
| Inclination | 15.849° |
| 230.116° | |
| 111.400° | |
| Physical characteristics | |
Mean radius | 45.39±2 km[1] 45.39 km[2] |
| 5.925 h (0.2469 d)[1][3] | |
| 0.046[2] 0.0460±0.004[1] | |
| 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. 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.
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[edit]
- ^ a b c d e Yeomans, Donald K., "694 Ekard", JPL Small-Body Database Browser, NASA Jet Propulsion Laboratory, retrieved 7 May 2016.
- ^ a b c d 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.
- ^ a b 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.
- ^ 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.
- ^ 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[edit]
- 694 Ekard at AstDyS-2, Asteroids—Dynamic Site
- 694 Ekard at the JPL Small-Body Database
