757 Portlandia
757 Portlandia is a main-belt asteroid 32 km in diameter. It was discovered on 30 September 1908 from Taunton, Massachusetts by the amateur American astronomer Joel E. Metcalf. The asteroid was named for the city of Portland, Maine, where Hastings was a church minister at the time. In November 2015, amateur astronomers captured it with images of comet 67P/Churyumov–Gerasimenko. Portlandia came to opposition in March 2016 at apparent magnitude 13.2.
| Discovery | |
|---|---|
| Discovered by | Joel Hastings Metcalf |
| Discovery site | Taunton, Massachusetts |
| Discovery date | 30 September 1908 |
| Designations | |
MPC designation | (757) Portlandia |
Alternative designations | 1908 EJ |
| Orbital characteristics | |
| Epoch 31 July 2016 (JD 2457600.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 99.16 yr (36218 d) |
| Aphelion | 2.6327 AU (393.85 Gm) |
| Perihelion | 2.1142 AU (316.28 Gm) |
Semi-major axis | 2.3734 AU (355.06 Gm) |
| Eccentricity | 0.10922 |
Orbital period (sidereal) | 3.66 yr (1335.6 d) |
Mean anomaly | 133.453° |
Mean motion | 0° 16m 10.38s / day |
| Inclination | 8.1694° |
Longitude of ascending node | 22.515° |
| 44.204° | |
| Physical characteristics | |
Mean radius | 16.045±0.7 km |
Synodic rotation period | 6.5837 h (0.27432 d) |
| 0.1427±0.014 | |
| M | |
| 12.3 to 15.7 | |
| 10.20 | |
This body is orbiting at a distance of 2.37 AU with a period of 3.66 years and an eccentricity of 0.109. The orbital plane is inclined at an angle of 8.2° to the plane of the ecliptic. 757 Portlandia is classified as an X-type asteroid and is a core member of the proposed Athor asteroid family, named after 161 Athor. This asteroid spans a girth of 32.89±0.24 km and is rotating with a period of 6.58 hours. During 2003, the asteroid was observed occulting a star. The resulting chords were used to determine a diameter estimate of 36.7 km.