Comets and Asteroids
Minor planet 18 Melpomene.
Minor planet 18 Melpomene reaches opposition on 21 March in the constellation of Virgo. This is a large, main-belt asteroid measuring 170x155x129km. Its orbit brings it as close as 268.5 million km (1.8 AU) to the Sun at perihelion and out as far as 418.4 million km (2.8 AU) at aphelion. It takes 1,270.6 days (3.5 years) to complete one orbit.
Melpomene is an S-type, silicaceous asteroid with a stony composition. It is relatively bright, varying between mag. +7.5 and +12.0. The 2018 opposition isn’t particularly favourable in this respect, Melpomene reaching a maximum magnitude of +10.2. At the start of March, it’ll appear at mag. +10.5, slowly brightening to mag. +10.2 by the 18th. It remains at this brightness through to the 24th, dimming back to mag. +10.4 by 31 March.
Melpomene’s path takes it across a section of the Bowl of Virgo, a region rich in galaxies and there’s an opportunity to watch it slowly track past some of these objects throughout the month. On the nights of 6/7 and 7/8 March, Melpomene appears close to NGC 4378 a mag. +11.7 spiral galaxy located 1° northeast of mag. +10.1 M61.
On the night of 9/10 March, Melpomene passes 20 arcminutes northeast of the mag. +11.6 lenticular galaxy NGC 4324. On 13/14 March the minor planet passes mag. +10.4 elliptical galaxy NGC 4261 and +11.8 barred-spiral NGC 4260. Melpomene passes less than 10 arcminutes northeast of NGC 4260 on the night of 14/15 March. Then on the night of 30/31 March, Melpomene completes its crossing of the Bowl of Virgo and sits 12 arcminutes south of the mag. +4.1 star Omicron (k) Virginis.
Melpomene was found by the English astronomer John Russell Hind on 24 June 1852 and, following the occultation of a star on 11 December 1978 was believed to have its own moon. Later observations by the Hubble Space Telescope revealed the asteroid’s elongated shape but no presence of a moon.
18 Melpomene seems to slowly track out of the Bowl of Virgo in March