18 Melpomene

The 18th asteroid ever found, by a very young British astronomer with no college degree but a diploma from Nottingham High School who later directed two observatories and was responsible for the Nautical Almanac (more at a later date on him). I will not bore the reader at this late juncture with my use of ©Keynote on iMac as a light table, comparing the star charts of ©SkySafari Pro in semi-opacity to my star field images of 18 Melpomene. Taken early last night from my balcony.

κ Cancri is labelled in both, the white B8 giant.

18 Melpomene is a large main-belt asteroid discovered by J. R. Hind in June, 1852. It was named after Melpomene, the muse of tragedy in Greek mythology. Shed no tears, however. It is a decent-sized asteroid with a typical periodicity.

Melpomene’s orbital period is 3.48 years, and its average distance from the Sun is 2.97 AU. It has approximate physical dimensions of 170 x 155 x 129 km. Melpomene was observed with the Hubble Space Telescope in 1993. HST resolved the asteroid’s slightly elongated shape, but no satellites were detected. Both important qualities for a “space-craft emergency landing field” of the near-future.

Melpomene is classified as an S-type (stony) asteroid, and is composed of silicates and metals.

Imaging Observations of Asteroids with Hubble Space Telescope☆

Icarus, Volume 137, Issue 2, 1 February 1999, Pages 260-268

AlexStorrs, BenWeiss, BenZellner, WinBurleson, Rukmini Sichitiu, EddieWells, CharlesKowal, DavidTholen


“We present the results of two Hubble Space Telescope (HST) observing programs, consisting of 11 imaging observations of 10 asteroids. The primary focus of the projects was to search for faint companions (satellites) of these asteroids. No binary systems were detected. More specifically, no companions were found at more than 0.1 arcsec separation of brightness down to 4 magnitudes fainter than the primary asteroid. No companions down to 6 magnitudes fainter than the primary asteroid were found at more than 0.5 arcsec separation. It is unlikely that companions more than 6 magnitudes fainter than a well-exposed primary would be detected. These nondetections place very stringent limits on the existence of companion bodies for these asteroids. A secondary goal was to resolve the illuminated portion of the asteroids. Nine of the 10 asteroids were marginally resolved, with three of these—9 Metis, 18 Melpomene, and 19 Fortuna—showing significant extension and brightness variations up to a factor of two across the illuminated portion of the restored image. The diameters of the resolved asteroids are generally in good agreement with those in the TRIAD II file (E. F. Tedesco, 1989, InAsteroids II(Binzel, Gehrels, and Matthews, Eds.)). Diameters for 19 Fortuna and 624 Hektor (which are not in the TRIAD file) have been measured: 225 and 370×195 km, respectively.”

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