1928 Summa
Main-belt asteroid
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1928 Summa, provisional designation 1938 SO, is a stony asteroid from the inner regions of the asteroid belt, approximately 9 kilometers in diameter.
| Discovery[1] | |
|---|---|
| Discovered by | Y. Väisälä |
| Discovery site | Turku Obs. |
| Discovery date | 21 September 1938 |
| Designations | |
| (1928) Summa | |
Named after | Finnish village (Battle of Summa)[2] |
| 1938 SO · 1969 PA | |
| main-belt · (inner)[3] | |
| Orbital characteristics[1] | |
| Epoch 4 September 2017 (JD 2458000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 78.38 yr (28,628 days) |
| Aphelion | 2.9797 AU |
| Perihelion | 1.9733 AU |
| 2.4765 AU | |
| Eccentricity | 0.2032 |
| 3.90 yr (1,423 days) | |
| 98.003° | |
| 0° 15m 10.44s / day | |
| Inclination | 4.5756° |
| 180.42° | |
| 157.80° | |
| Physical characteristics | |
| Dimensions | 8.34 km (derived)[3] 9.333±0.170 km[4][5] |
| 6.8549±0.0006 h[6] 6.855±0.001 h[7] 9.66 h (dated)[8] | |
| 0.160±0.043[4][5] 0.20 (assumed)[3] | |
| S[3][8] B–V = 1.010[1] | |
| 12.68[1] · 12.76[3][4][8] · 13.20±0.85[9] | |
It was discovered on 21 September 1938, by Finnish astronomer Yrjö Väisälä at Turku Observatory in Southwest Finland.[10] It was named for a Finnish village where the Battle of Summa took place.[2]
Orbit and classification
Summa is a S-type asteroid that orbits the Sun in the inner main-belt at a distance of 2.0–3.0 AU once every 3 years and 11 months (1,423 days). Its orbit has an eccentricity of 0.20 and an inclination of 5° with respect to the ecliptic.[1] The body's observation arc begins at Turku one night after its official discovery observation, with no precoveries taken, and no prior identifications made.[10]
Rotation period
In March 1984, the first but poorly rated rotational lightcurve of Summa was obtained from photometric observations by American astronomer Richard Binzel. It gave a rotation period of 9.66 hours with a brightness amplitude of 0.14 magnitude (U=1).[8]
In August 2012, a refined yet ambiguous lightcurve with a period of 6.855 hours and an amplitude of 0.13 was obtained by Larry E. Owings at the Barnes Ridge Observatory in California (U=2+). Lightcurve analysis also considered that Summa might be a binary system.[7] One month later, the so-far best rated lightcurve from British astronomer Kevin Hills using the remote controlled Riverland Dingo Observatory in Australia, gave a period of 6.8549 hours with a brightness amplitude of 0.18 (U=3).[6]
Diameter an albedo
According to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Summa measures 9.333 kilometers in diameter and its surface has an albedo of 0.160,[4][5] while the Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 8.34 kilometers with an absolute magnitude of 12.76.[3]
Naming
This minor planet was named after the village on the Karelian Isthmus, where the Battle of Summa took place during the Finnish Winter War (1939–1940).[2] The approved naming citation was published by the Minor Planet Center on 1 August 1980 (M.P.C. 5450).[11] Most of Yrjö Väisälä's discoveries have names that relate in one way or another to this military conflict between Finland and the Soviet Union during World War II.
