115 Thyra

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115 Thyra
115Thyra (Lightcurve Inversion).png
A three-dimensional model of 115 Thyra based on its light curve.
Discovered by James Craig Watson
Discovery date August 6, 1871
Named after
Main belt
Orbital characteristics[1]
Epoch December 31, 2006 (JD 2454100.5)
Aphelion 424.287 Gm (2.836 AU)
Perihelion 287.821 Gm (1.924 AU)
356.054 Gm (2.380 AU)
Eccentricity 0.192
1341.169 d (3.67 a)
19.13 km/s
Inclination 11.600°
Physical characteristics
Dimensions 79.83[2] km
Mass 5.3×1017 kg
0.0223 m/s²
0.0422 km/s
Albedo 0.275[2]
Temperature ~180 K
Spectral type

115 Thyra is a fairly large and bright inner main-belt asteroid that was discovered by Canadian-American astronomer J. C. Watson on August 6, 1871[4] and was named for Thyra, the consort of King Gorm the Old of Denmark. Based upon its spectrum, it is categorized as a stony S-type asteroid.[5]

Observations made between 1978 and 1981 produced a composite light curve with two minima and maxima. However, a subsequent study in 1983 only found a single minima and maxima. A synodical rotation period of 7.241 hours was determined. This was confirmed by observations between 1995 and 2000. The changes in brightness and color indicate a surface with an uneven composition.[6]

The asteroid has a slightly elongated shape, with a ratio of 1.20 between the lengths of the major and minor axes. The orbital longitude and latitude of the asteroid pole in degrees is estimated to be (λ0, β0) = (68°, 23°).[7] Measurements of the thermal inertia of 115 Thyra give a value of around 75 m−2 K−1 s−1/2, compared to 50 for lunar regolith and 400 for coarse sand in an atmosphere.[2]


  1. ^ Yeomans, Donald K., "115 Thyra", JPL Small-Body Database Browser (NASA Jet Propulsion Laboratory), retrieved 2013-03-25. 
  2. ^ a b c d Delbo', Marco; Tanga, Paolo (February 2009), "Thermal inertia of main belt asteroids smaller than 100 km from IRAS data", Planetary and Space Science 57 (2): 259–265, arXiv:0808.0869, Bibcode:2009P&SS...57..259D, doi:10.1016/j.pss.2008.06.015. 
  3. ^ *JPL Small-Body Database Browser
  4. ^ "Numbered Minor Planets 1–5000", Discovery Circumstances (IAU Minor Planet center), retrieved 2013-04-07. 
  5. ^ DeMeo, Francesca E. et al. (July 2009), "An extension of the Bus asteroid taxonomy into the near-infrared" (PDF), Icarus 202 (1): 160–180, Bibcode:2009Icar..202..160D, doi:10.1016/j.icarus.2009.02.005, retrieved 2013-04-08.  See appendix A.
  6. ^ Michałowski, T. et al. (March 2004), "Photometry and models of selected main belt asteroids I. 52 Europa, 115 Thyra, and 382 Dodona", Astronomy and Astrophysics 416: 353–366, Bibcode:2004A&A...416..353M, doi:10.1051/0004-6361:20031706. 
  7. ^ Kryszczyńska, A. et al. (December 2007), "New findings on asteroid spin-vector distributions", Icarus 192: 223–237, Bibcode:2007Icar..192..223K, doi:10.1016/j.icarus.2007.06.008.