2478 Tokai
Stony Florian binary asteroid discovered in 1981 by Toshimasa Furuta.
2478 Tokai (1981 JC) is a stony asteroid from the inner main belt, belonging to the Flora family and forming a binary system. Roughly 10 kilometers across, it was discovered on 4 May 1981 by Japanese astronomer Toshimasa Furuta at Tōkai Observatory in Japan. Its orbit carries it between 2.1 and 2.4 astronomical units from the Sun, completing one revolution every 3 years and 4 months (1,213 days), with a low eccentricity of 0.07 and an inclination of 4° to the ecliptic. Classified as an S-type in the SMASS scheme, its diameter ranges from 9.2 to 10.1 kilometers based on data from the Akari satellite and the WISE/NEOWISE surveys, with albedo values between 0.144 and 0.33; the Collaborative Asteroid Lightcurve Link, following Petr Pravec’s revised WISE data, gives an albedo of 0.1957 and a diameter of 10.09 kilometers at an absolute magnitude of 12.37. Photometric observations in 2007 revealed a moon orbiting Tokai, roughly 6 kilometers in diameter (lower-limit diameter ratio of 0.72), with an orbital period of 25.88 hours. The asteroid was named after the city of Tōkai, Japan, home to both the discoverer and the discovering observatory; the naming citation was published by the Minor Planet Center on 8 February 1982 (M.P.C. 6650).
Quick Facts
- Minorplanet
- yes
- Background
- #D6D6D6
- Discovered
- 4 May 1981
- Discoverer
- T. Furuta
- Discovery Site
- Tōkai Obs. (879)
- Mpc Name
- (2478) Tokai
- Pronounced
- ' · t · ou · k · ai / ja · toːkai · lang
- Named After
- Tōkai (Japanese city)
- Mp Category
- main-beltFlora
- Epoch
- 4 September 2017 (JD 2458000.5)
- Uncertainty
- 0
- Observation Arc
- 84.68 yr (30,929 days)
Facts from the source article.
Lore & Background
2478 Tokai is a member of the Flora family, one of the largest groups of stony asteroids in the main-belt. It orbits the Sun in the inner main-belt at a distance of 2.1–2.4 AU once every 3 years and 4 months (1,213 days), with an eccentricity of 0.07 and an inclination of 4° relative to the ecliptic. In the SMASS classification, it is a common S-type asteroid.
Photometric observations in 2007 revealed a minor-planet moon in orbit of Tokai, measuring approximately 6 kilometers in diameter (lower limit diameter ratio of 0.72) and having an orbital period of 25.88 hours. The asteroid was named after the city of Tōkai, Japan, where the discoverer lives and the discovering observatory is located. The naming citation was published by the Minor Planet Center on 8 February 1982 (M.P.C. 6650).
Reader's Guide
2478 Tokai is significant as a binary asteroid system, with a moon approximately 6 kilometers in diameter discovered through photometric observations in 2007. Its stony composition and membership in the Flora family place it among the common S-type asteroids in the inner main-belt. The asteroid's diameter, measured by the Japanese Akari satellite and NASA's WISE/NEOWISE surveys, ranges from about 9.2 to 10.1 kilometers, with albedo values between 0.144 and 0.33. The Collaborative Asteroid Lightcurve Link agrees with Petr Pravec's revised WISE-data, giving an albedo of 0.1957 and a diameter of 10.09 kilometers. Its discovery by Japanese astronomer Toshimasa Furuta at Tōkai Observatory and naming after the city of Tōkai highlight its local significance. The binary nature of Tokai contributes to the study of asteroid satellite systems, though uncertainties in its physical parameters remain from the various surveys.
Did You Know?
- It is a binary system with a moon approximately 6 kilometers in diameter, discovered in 2007.
- The asteroid measures between 9.238 and 10.09 kilometers in diameter according to different surveys.
Frequently Asked Questions
Who discovered 2478 Tokai and when?
Japanese astronomer Toshimasa Furuta first observed this asteroid on 4 May 1981 from Tōkai Observatory in Japan. It entered the catalogue under the provisional label 1981 JC before being assigned its permanent number.
What type of asteroid is 2478 Tokai?
It is an S-type (stony) body in the SMASS classification and belongs to the Flora family in the inner main belt. The object is also a binary system, meaning a smaller companion orbits alongside it.
How large is 2478 Tokai?
Its diameter falls in the range of about 9.2 to 10.1 kilometers, with a geometric albedo estimated between 0.144 and 0.33. These figures are derived primarily from infrared measurements taken by the Akari satellite.
What does 2478 Tokai's orbit look like?
It circles the Sun between roughly 2.1 and 2.4 AU, completing one full revolution in about 3 years and 4 months (1,213 days). The path is nearly circular with an eccentricity of just 0.07 and only a 4-degree tilt to the ecliptic.
Why is 2478 Tokai notable among main-belt asteroids?
Its Flora-family membership links it to one of the most populous stony groups in the inner belt, while its binary configuration makes it a useful natural laboratory for studying how small bodies gravitationally pair up. The very low eccentricity and inclination also mark it as a dynamically stable resident of that region.
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