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S-type Asteroid





CHARACTERISTICS

S-types are moderately bright (with an Albedo of 0.10 to 0.22) and consist of Metallic Nickel - Iron mixed with iron- and Magnesium - Silicates .
They are dominant in the inner Main Belt within 2.2 AU , common in the central belt within about 3 AU , but become rare further out. The largest is 15 Eunomia (about 330 km wide across its longest dimension), with other large members being 3 Juno and 9 Metis .

Their spectrum has a moderately steep slope at wavelengths shorter than 0.7 μm, and has moderate to weak absorption features around 1 μm and 2 μm. The 1 μm absorption is indicative of the presence of Silicate s (stony minerals). Often there is also a broad but shallow absorption feature centered near 0.63 μm. The composition of these asteroids is similar to a variety of stony Meteorites which share similar spectral characteristics.


S-GROUP ASTEROIDS

See also Asteroid Spectral Types

SMASS classification

In the SMASS Classification , several generally "stony" types of asteroids are brought together into a wider S-group which contains the following types:
  • A-type

  • K-type

  • L-type

  • Q-type

  • R-type

  • a core S-type for asteroids having the most "typical" spectra for the S-group

  • Sa, Sk, Sl, Sq, and Sr-types containing transition objects between the core S-type and the A, K, L, Q, and R-types, respectively.

  • This whole "S" assemblage of asteroids is spectrally quite distinct from the carbonaceous C-group and the mostly metallic X-group .



Tholen classification

In the Tholen Classification the S-type is a very broad grouping which includes all the types in the SMASS S-group except for the A , Q , and R , which have particularly strong "stony" absorption features around 1 μm.


SEE ALSO



REFERENCES

  • S. J. Bus and R. P. Binzel ''Phase II of the Small Main-belt Asteroid Spectroscopy Survey: A feature-based taxonomy'', Icarus, Vol. 158, pp. 146 (2002).