Venus and Jupiter drift apart, blue moon ap­pears later in July

The Guardian (Charlottetown) - - FEATURES/ENTERTAINMENT - Glenn Roberts Glenn K. Roberts is a mem­ber of the Char­lot­te­town Cen­tre of the Royal As­tro­nom­i­cal So­ci­ety of Canada (RASC). His col­umn ap­pears in The Guardian once a month. He wel­comes com­ments from read­ers. Any­one who would like to com­ment on his col­umn

Hav­ing just com­pleted their close con­junc­tion on the last evening of June, Venus and Jupiter are now slowly draw­ing apart from one another in the evening sky. Shortly af­ter sunset, the two plan­ets are vis­i­ble half way up the western sky. Venus (mag. - 4.6) sits to the left of Jupiter (mag. - 1.8), and slowly drifts fur­ther to the SW away from Jupiter as the month pro­gresses.

At mid-month, Venus has bright­ened slightly to mag. - 4.7, its peak bright­ness for this evening ap­pari­tion. As July opens, the two plan­ets are paired for about two hours be­fore drop­ping be­low the western hori­zon. By the end of the month, Venus will fol­low the sun down about 30 min­utes af­ter­ward, with Jupiter set­ting a half hour later.

To the up­per left of Venus sits Reg­u­lus, the bright­est star in the con­stel­la­tion of Leo the Lion. Reg­u­lus is the “dot” star in the re­versed ques­tion mark as­ter­ism that forms the head and shoul­ders of the lion. Venus, Jupiter and Reg­u­lus form a con­stantly chang­ing tri­an­gle con­fig­u­ra­tion through­out the month. On the evening of the 18th, the slen­der, cres­cent moon joins the pic­ture, mak­ing for a great photo op­por­tu­nity. By the end of the month, about one hour af­ter sunset, both plan­ets are lost from sight in the evening twi­light.

Saturn is the next naked-eye planet to be­come vis­i­ble, ap­pear­ing about 30 de­grees above the south­ern hori­zon as dark­ness falls. By mid-month, Saturn shines at + 0.3 mag., easily the bright­est ob­ject in that area of the sky. On the night of July 2526, the wax­ing, gib­bous moon sits just to the north (up­per right) of Saturn. Though it will be hard to dis­tin­guish with the naked eye, Saturn dims slightly as July pro­gresses, drop­ping from mag. + 0.2 to + 0.4. Saturn’s ma­jes­tic rings are tilted at 24 de­grees to our line of sight in July.

Mer­cury shines brightly in the morn­ing twi­light dur­ing the first two weeks of July. About a half hour be­fore sunrise, Mer­cury can be spot­ted about eight de­grees above the ENE hori­zon. By the third week of July, Mer­cury drops deep into the gath­er­ing twi­light, un­til on July 23 it slips be­hind the sun (su­pe­rior con­junc­tion) and is lost from sight al­to­gether.

The only me­teor shower of note this month is the South­ern Delta Aquari­ids (ra­di­ant in Aquarius - the wa­ter bearer). Ac­tive from around July 12 to the 23rd of Au­gust, this shower’s peak will come dur­ing the predawn hours of July 30. Un­for­tu­nately, this is only one day be­fore the blue moon - the sec­ond full moon of July, on the 31st, so the light from the near-full moon will re­duce the num­ber of me­te­ors seen dur­ing the peak (nor­mally 15-20/hr).

The first full moon was on July 1. How­ever, get­ting out on the morn­ings of July 27-29 will pro­vide a brief win­dow of op­por­tu­nity be­tween moon set and the start of morn­ing twi­light, dur­ing which time you might see as many as 12-15 me­te­ors/hr.

As men­tioned above, July has two full moons - July 1 and 31. The sec­ond full moon oc­cur­ring in any given month is re­ferred to as a blue moon. This is not to be con­fused with when the moon takes on a bluish colour due to dust par­ti­cles in the up­per at­mos­phere. July’s blue moon is the first since Au­gust 2012.

Un­til next month, clear skies.

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