1757 Porvoo

1757 Porvoo, provisional designation 1939 FC, is a presumably stony asteroid from the inner regions of the asteroid belt, approximately 10 kilometers in diameter. It was discovered on 17 March 1939, by Finnish astronomer Yrjö Väisälä at Turku Observatory on the coast of southwestern Finland.[8] The asteroid was named for the Finnish city of Porvoo.[2]

1757 Porvoo
Discovery [1]
Discovered byY. Väisälä
Discovery siteTurku Obs.
Discovery date17 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 arc77.87 yr (28,442 days)
Aphelion2.6478 AU
Perihelion2.0551 AU
2.3514 AU
Eccentricity0.1260
3.61 yr (1,317 days)
263.06°
0° 16m 23.88s / day
Inclination3.9765°
39.423°
149.40°
Physical characteristics
Dimensions6.32 km (calculated)[3]
10.03±2.85 km[4]
12.81±0.45 km[5]
4.89 h[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]

    Orbit and classification

    Porvoo orbits the Sun in the inner main-belt at a distance of 2.1–2.6 AU once every 3 years and 7 months (1,317 days). Its orbit has an eccentricity of 0.13 and an inclination of 4° with respect to the ecliptic.[1] As no precoveries were taken, and no prior identifications were made, Porvoo's observation arc begins with its official discovery observation.[8]

    Physical characteristics

    Rotation period

    In the early 1980s, a rotational lightcurve of Porvoo was obtained from photometric observations taken by American astronomer Richard P. Binzel using the 0.91- and 2.1-m telescopes at the University of Texas McDonald Observatory. It gave it a well-defined rotation period of 4.89 hours with a brightness variation of 0.30 magnitude (U=3).[6]

    Diameter and albedo

    According to the surveys carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Porvoo measures 10.03 and 12.81 kilometers in diameter, and its surface has an albedo of 0.049 and 0.073, respectively.[4][5]

    The Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 – contrary to the rather carbonaceous albedo given by the space-based surveys – and calculates a diameter of 6.32 kilometers with an absolute magnitude of 13.36.[3]

    Naming

    This minor planet was named for Porvoo, 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 after Turku, location of the discovering observatory. In 1809, at the Diet 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 the Minor Planet Center on 1 August 1980 (M.P.C. 5449).[9]

    References
    1. "JPL Small-Body Database Browser: 1757 Porvoo (1939 FC)" (2017-01-28 last obs.). Jet Propulsion Laboratory. Retrieved 8 June 2017.
    2. Schmadel, Lutz D. (2007). "(1757) Porvoo". Dictionary of Minor Planet Names – (1757) Porvoo. Springer Berlin Heidelberg. p. 140. doi:10.1007/978-3-540-29925-7_1758. ISBN 978-3-540-00238-3.
    3. "LCDB Data for (1757) Porvoo". Asteroid Lightcurve Database (LCDB). Retrieved 20 December 2016.
    4. Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Nugent, C.; et al. (November 2012). "Preliminary Analysis of WISE/NEOWISE 3-Band Cryogenic and Post-cryogenic Observations of Main Belt Asteroids". The Astrophysical Journal Letters. 759 (1): 5. arXiv:1209.5794. Bibcode:2012ApJ...759L...8M. doi:10.1088/2041-8205/759/1/L8. Retrieved 20 December 2016.
    5. Usui, Fumihiko; Kuroda, Daisuke; Müller, Thomas G.; Hasegawa, Sunao; Ishiguro, Masateru; Ootsubo, Takafumi; et al. (October 2011). "Asteroid Catalog Using Akari: AKARI/IRC Mid-Infrared Asteroid Survey". Publications of the Astronomical Society of Japan. 63 (5): 1117–1138. Bibcode:2011PASJ...63.1117U. doi:10.1093/pasj/63.5.1117. Retrieved 17 October 2019. (online, AcuA catalog p. 153)
    6. Binzel, R. P.; Mulholland, J. D. (December 1983). "A photoelectric lightcurve survey of small main belt asteroids". Icarus. 56 (3): 519–533. Bibcode:1983Icar...56..519B. doi:10.1016/0019-1035(83)90170-7. ISSN 0019-1035. Retrieved 20 December 2016.
    7. Veres, Peter; Jedicke, Robert; Fitzsimmons, Alan; Denneau, Larry; Granvik, Mikael; Bolin, Bryce; et al. (November 2015). "Absolute magnitudes and slope parameters for 250,000 asteroids observed by Pan-STARRS PS1 - Preliminary results". Icarus. 261: 34–47. arXiv:1506.00762. Bibcode:2015Icar..261...34V. doi:10.1016/j.icarus.2015.08.007. Retrieved 20 December 2016.
    8. "1757 Porvoo (1939 FC)". Minor Planet Center. Retrieved 20 December 2016.
    9. "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 20 December 2016.

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