| Discovery[1] | |
|---|---|
| Discovered by | Y. Väisälä |
| Discovery site | Turku Obs. |
| Discovery date | 17 March 1939 |
| Designations | |
| (1757) Porvoo | |
Named after | Porvoo(Finnish city)[2] |
| 1939 FC · 1964 BB 1968 FK | |
| main-belt · (inner)[3] | |
| Orbital characteristics[1] | |
| Epoch 4 September 2017 (JD 2458000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 77.87 yr (28,442 days) |
| Aphelion | 2.6478AU |
| Perihelion | 2.0551 AU |
| 2.3514 AU | |
| Eccentricity | 0.1260 |
| 3.61yr (1,317 days) | |
| 263.06° | |
| 0° 16m 23.88s / day | |
| Inclination | 3.9765° |
| 39.423° | |
| 149.40° | |
| Physical characteristics | |
| Dimensions | 6.32 km(calculated)[3] 10.03±2.85 km[4] 12.81±0.45 km[5] |
| 4.89h[6] | |
| 0.049±0.004[5] 0.072±0.097[4] 0.073±0.082 0.20(assumed)[3] | |
| S[3] | |
| 13.36[1][3][5] · 13.47[4] · 13.49±0.26[7] | |
1757 Porvoo, provisional designation1939 FC, is a presumably stonyasteroid from the inner regions of theasteroid belt, approximately 10 kilometers in diameter. It was discovered on 17 March 1939, by Finnish astronomerYrjö Väisälä atTurku Observatory on the coast of southwestern Finland.[8] The asteroid was named for the Finnish city ofPorvoo.[2]
Porvoo orbits the Sun in theinner main-belt at a distance of 2.1–2.6 AU once every 3 years and 7 months (1,317 days). Its orbit has aneccentricity of 0.13 and aninclination of 4° with respect to theecliptic.[1] As noprecoveries were taken, and no prior identifications were made,Porvoo'sobservation arc begins with its official discovery observation.[8]
In the early 1980s, a rotationallightcurve ofPorvoo was obtained from photometric observations taken by American astronomerRichard P. Binzel using the 0.91- and 2.1-m telescopes at the University of TexasMcDonald Observatory. It gave it a well-definedrotation period of 4.89 hours with a brightness variation of 0.30magnitude (U=3).[6]
According to the surveys carried out by NASA'sWide-field Infrared Survey Explorer with its subsequentNEOWISE mission,Porvoo measures 10.03 and 12.81 kilometers in diameter, and its surface has analbedo of 0.049 and 0.073, respectively.[4][5]
TheCollaborative Asteroid Lightcurve Link assumes a standard albedo forstony asteroids of 0.20 – contrary to the rathercarbonaceous albedo given by the space-based surveys – and calculates a diameter of 6.32 kilometers with anabsolute magnitude of 13.36.[3]
Thisminor planet was named forPorvoo, Finnish city and municipality located on the southern coast of Finland, and east of the capital Helsinki.[2]
Porvoo is one of the six medieval towns in Finland, and is its second oldest city afterTurku, location of the discovering observatory. In 1809, at theDiet of Porvoo, the Russian czar confirmed that Finland was annexed to the Russian empire as an autonomous nation.[2] The official naming citation was published by theMinor Planet Center on 1 August 1980 (M.P.C. 5449).[9]
