18 Melpomene

(JD 2460600.5) (150 × 125 km) (150 × 170 km)

3.0 kg

11.573 hours 6.51 0.223 0.181 ± 0.033

18 Melpomene is a large, bright main-belt asteroid that was discovered by J. R. Hind on 24 June 1852, and named after Melpomenē, the Muse of tragedy in Greek mythology. Its historical symbol was a dagger over a star; it was encoded in Unicode 17.0 as U+1CECB 𜻋 ([[File:Melpomene symbol (fixed width).svg|12px|class=skin-invert]]).{{cite web | access-date = September 9, 2025 | url-status = live

Melpomene is classified as an S-type asteroid and is composed of silicates and metals. This asteroid is orbiting the Sun at a distance of 343.443 Gm with a period of 1270.552 days and an eccentricity (ovalness) of 0.22. The orbital plane is tilted at an angle of 10.1° to the plane of the ecliptic.

Melpomene occulted the star SAO 114159 on 11 December 1978. A possible Melpomenean satellite with a diameter of at least 37 km was detected. The satellite candidate received a provisional designation S/1978 (18) 1. In 1988 a search for satellites or dust orbiting this asteroid was performed using the UH88 telescope at the Mauna Kea Observatories, but the effort came up empty. Melpomene was observed with the Hubble Space Telescope in 1993. It was able to resolve the asteroid's slightly elongated shape, but no satellites were detected.

Melpomene has been studied by radar. Photometric observations during 2012 provided a rotation period of with a brightness variation of in magnitude, which is consistent with previous studies. It has a mean diameter of .

Melpomene can reach an apparent magnitude of +7.9 at a favorable opposition near perihelion, such as occurred in September 2002 when it was 0.814 AU from Earth.