Comet 46P/Wir­ta­nen

Sky at Night Magazine - - THE SKY GUIDE -

WHEN: All month; bright­en­ing to­wards the end of Septem­ber

Comet 46P/Wir­ta­nen is set to put on a show for the north­ern hemi­sphere over the next few months. A short-pe­riod comet or­bit­ing the Sun ev­ery 5.4 years, Wir­ta­nen is no­to­ri­ous be­cause it was the orig­i­nal tar­get for ESA’s Rosetta mis­sion. A missed launch win­dow re-di­rected Rosetta to 67P/Churyu­mov-Gerasi­menko and the rest, as they say, is his­tory.

Dis­cov­ered on 17 Jan­uary 1948 by Amer­i­can as­tronomer Carl A Wir­ta­nen, 46P be­longs to the Jupiter fam­ily of comets. These have aphe­lia – great­est dis­tance from the Sun – be­tween 5 and 6 AU and are in­flu­enced by Jupiter’s grav­ity.

Wir­ta­nen’s next per­i­he­lion – clos­est ap­proach to the Sun – oc­curs on 12 De­cem­ber 2018, co­in­cid­ing with a par­tic­u­larly favourable 11.7 mil­lion km ap­proach to Earth on 16 De­cem­ber. Con­se­quently, 46P/Wir­ta­nen could get as bright as third mag­ni­tude; an easy naked-eye ob­ject. A world-wide ob­serv­ing cam­paign has been or­gan­ised to cap­i­talise on this favourable ap­pear­ance, Wir­ta­nen re­tain­ing tar­get po­ten­tial for fu­ture ex­plo­rative space mis­sions.

At present Wir­ta­nen is low in Ce­tus, track­ing be­low mag. +3.5 Tau (o) Ceti. It is cur­rently around mag. +11.8. Dur­ing Septem­ber its po­si­tion wors­ens, reach­ing a point 4° west of mag. +4.0 Up­silon (p) Ceti on the night of 13/14 Septem­ber when it should be a mag­ni­tude brighter than it was at the start of the month. From here it dives rapidly south­ward, all the while get­ting brighter. It’s most southerly po­si­tion oc­curs at the start of Novem­ber when, at mag. +7.0, it’ll be in For­nax at dec­li­na­tion –33°.

For the rest of Novem­ber it ac­cel­er­ates north, of­fi­cially leav­ing For­nax on 28 Novem­ber and pass­ing back into Ce­tus. At this time it should be naked-eye vis­i­ble, around mag. +5.1. Pre­dicted to be mag. +4.5 on 5 De­cem­ber, it passes close to mag. +4.2 Pi (/) Ceti as it moves into Eri­danus. On 7 De­cem­ber, rapidly mov­ing north, the mag. +4.3 comet ap­pears close to mag. +3.9 Eta (d) Eri­dani.

The fourth mag­ni­tude comet then passes west of mag. +2.5 Menkar (Al­pha (_) Ceti) on the morn­ing of 11 De­cem­ber and slips into Taurus on the morn­ing of 12 De­cem­ber. It tracks be­tween the Pleiades and Hyades open clus­ters on the morn­ing and evening of 16 De­cem­ber when it’s also clos­est to Earth. It’s pre­dicted to be an easy naked-eye mag. +3.8 ob­ject at this time.

Fad­ing to mag. +4.2, Wir­ta­nen passes close to bright Capella (Al­pha (_) Auri­gae) on the night of 23 De­cem­ber. It’ll prob­a­bly re­main naked eye un­til the first week of Jan­uary 2019 when, at around sixth mag­ni­tude, it moves into Ursa Ma­jor.

The path of 46P/Wir­ta­nen for the rest of the year. This month it trav­els through Ce­tus, the Whale

Clos­est to Earth in midDe­cem­ber, naked-eye comet Wir­ta­nen will pass be­tween the Pleiades (pic­tured) and Hyades open clus­ters

Newspapers in English

Newspapers from UK

© PressReader. All rights reserved.