Comets and As­ter­oids

Mi­nor planet 18 Melpomene.

Sky at Night Magazine - - CONTENTS -

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

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