Warmer weather, longer days mean spring is com­ing to an end

The Guardian (Charlottetown) - - THE ISLAND - Glenn Roberts

Warmer weather, longer days mean spring is com­ing to an end

Hur­ray, sum­mer is fi­nally here!

Well, it doesn’t of­fi­cially hap­pen un­til June 21, but the weather cer­tainly feels more sum­mer-like than it has for the past few weeks.

The sum­mer sol­stice oc­curs at 12:54 p.m. ADT on that date, mark­ing the of­fi­cial com­mence­ment of sum­mer here in the north­ern hemi­sphere (win­ter in the south­ern hemi­sphere). It also marks the long­est day of the year, and, sub­se­quently, the short­est night.

The cel­e­bra­tion of the sum­mer sol­stice has a long his­tory, span­ning many cen­turies and count­less global cul­tures, where an­cient peoples used the sum­mer sol­stice to or­ga­nize their cal­en­dars, work out when to plant crops and, in gen­eral, to cel­e­brate the end of the cold and con­fin­ing weather of win­ter and spring. The an­cient Celts of Europe are said to have cel­e­brated the ar­rival of sum­mer by danc­ing around huge bon­fires.

Un­for­tu­nately, for most peo­ple around the world nowa­days, it is just another day, and though they men­tally wel­come its ar­rival, there are few, if any, large, pub­lic cel­e­bra­tions. How­ever, in the north­ern Euro­pean coun­tries of Swe­den, Den­mark, Fin­land and Nor­way, the sum­mer sol­stice is still cel­e­brated with large, pub­lic fes­ti­vals that of­ten in­cor­po­rate mu­sic and danc­ing around a may­pole.

At the fa­mous, ne­olithic Stone­henge circle in Wilt­shire, Eng­land, cel­e­brants an­nu­ally gather, with much mer­ri­ment and fan­fare, to watch the sun rise above the hori­zon be­tween two of the henge’s huge stone mono­liths on the sol­stice.

With the re­turn of sum­mer, and the sum­mer con­stel­la­tions to our night sky, there is a par­tic­u­lar geo­met­ric shape that is vis­i­ble in the night sky at this time of the year. The Sum­mer Tri­an­gle, a tri­an­gu­lar-shaped as­ter­ism, can be formed by join­ing the three bright­est stars Deneb, Vega and Al­tair in the con­stel­la­tions of Cygnus (the Swan), Lyre (the Harp) and Aquila (the Ea­gle) re­spec­tively. Look for the Sum­mer Tri­an­gle di­rectly over­head on any clear night through­out the sum­mer months.

It is lo­cated in a star-rich por­tion of our galaxy’s Milky Way

– a broad, murky, dif­fuse band of stars (ap­pear­ing like spilt milk) and dust clouds stretching across the night sky from the north­east to the south­west (a beau­ti­ful sight in binoc­u­lars). Vega (mag. +0.03) is 25 light-years from Earth, with Deneb (mag. +1.25) at 3,550 lightyears and Al­tair (mag. +0.77) at 16.6 light-years. A light-year is how far light trav­els across the vac­uum of space in one Julian calendar year (365.25 days), ap­prox­i­mately 9.46 tril­lion kilo­me­ters. It is a mea­sure of as­tro­nom­i­cal dis­tance, not time.

On the nights of June 15-16, the wax­ing, gib­bous moon, Jupiter (to lower left) and Antares (the bright “heart” star of Scor­pius - the Scor­pion, to the lower right) form a tri­an­gle in the south­east sky about an hour after sun­set. The fol­low­ing evening, the near­full moon has moved to the lower left of Jupiter, with the three ce­les­tial ob­jects now form­ing a shal­low arc across the night sky, be­fore set­ting in the south­west just be­fore dawn.

The evening of June 18 will see the moon (one day past full) and Saturn (just above the moon) rise in tan­dem (less than one de­gree apart) in the south-south­east sky. Look for the “teapot” as­ter­ism in Sagittariu­s - the Archer to the right. On that same evening, just after sun­set, Mer­cury (now at mag. +0.1) and Mars (mag. +1.8) are vis­i­ble ex­tremely close to­gether in the west-north­west sky – an ex­cel­lent photo-op. Mer­cury reaches its great­est eastern (to the left of the sun) elon­ga­tion (an­gu­lar dis­tance be­tween Mer­cury and the Sun as seen from Earth) on June 23, ne­ces­si­tat­ing binoc­u­lars to lo­cate it amid the evening gloam­ing. Venus (mag. -3.8) con­tin­ues to rise in the east­north­east sky about one hour be­fore sun­rise through the bal­ance of June.

The Al­go­nquin tribes of North Amer­ica re­ferred to June’s full moon (June 17) as the strawberry moon be­cause this was the month when the wild straw­ber­ries were plen­ti­ful.

Euro­pean set­tlers to North Amer­ica re­ferred to it as the rose moon, the month when most roses be­gan to bloom.

Un­til next time, clear skies.

Glenn K. Roberts lives in Stratford, P.E.I., and has been an avid am­a­teur as­tronomer since he was a small child. His col­umn, At­lantic Skies, ap­pears ev­ery two weeks. He wel­comes com­ments from read­ers, and any­one who would like to do so is en­cour­aged to email him at glennkrobe­[email protected]

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