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23 Thalia<ref>Stressed on the second syllable, {{#invoke:IPAc-en|main}} thə-LY-ə.</ref> is a large main-belt asteroid. It was discovered by J. R. Hind on December 15, 1852, at the private observatory of W. Bishop, located in Hyde Park, London, England.<ref>{{#invoke:citation/CS1|citation |CitationClass=book }}</ref> Bishop named it after Thalia, the Muse of comedy and pastoral poetry in Greek mythology.<ref>{{#invoke:citation/CS1|citation |CitationClass=book }}</ref>

It is categorized as an S-type asteroid consisting of mainly of iron- and magnesium-silicates. This the second most common type of asteroid in the main belt. Based on analysis of the light curve, the object has a sidereal rotation period of 0.513202 ± 0.000002 days. An ellipsoidal model of the light curve gives an /b ratio of 1.28 ± 0.05.<ref>{{#invoke:Citation/CS1|citation |CitationClass=journal }}</ref>

With a semimajor axis of 2.628, the asteroid is orbiting between the 3:1 and 5:2 Kirkwood gaps in the main belt.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Its orbital eccentricity is larger than the median value of 0.07 for the main belt, and the inclination is larger than the median of below 4°. But most of the main-belt asteroids have an eccentricity of no more than 0.4 and an inclination of up to 30°, so the orbit of 23 Thalia is not unusual for a main-belt asteroid.<ref name="mpc">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Thalia has been studied by radar.<ref name="detected">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>