What­ever its color, rare ‘blue moon’ catches the gaze of as­tron­omy buffs

The China Post - - LOCAL -

As­tron­omy buffs in Tai­wan yesterday ob­served a rare “blue moon,” which refers to the ap­pear­ance of a sec­ond full moon in a cal­en­dar month and a say­ing that dates back to the Amer­i­can Farm­ers’ Al­manac, rather than re­fer­ring to the color, the Taipei As­tro­nom­i­cal Mu­seum said.

Just don’t ex­pect it to be “blue,” mu­seum re­searcher Chang Kueilan had said, not­ing that it would look like any other full moon.

The moon­rise, which took place at 6:23 p.m., was the sec­ond full moon in July, fol­low­ing the first one on July 2, the mu­seum said.

The moon was clearly vis­i­ble by look­ing up to the lower eastern sky any­time af­ter 6:30 p.m., said Chang.

Ac­cord­ing to Chang, the mod­ern us­age of “blue moon” can be at­trib­uted to a Sky & Te­le­scope Mag­a­zine mis­in­ter­pre­ta­tion.

In an ar­ti­cle pub­lished by the as­tron­omy mag­a­zine in 1946, it mis­tak­enly de­fined a blue moon as the sec­ond full moon in a cal­en­dar month, which is how it is un­der­stood to­day, Chang said.

The mag­a­zine said that 12 full moons are usu­ally per­ceiv­able each year, one in each cal­en­dar month, but that be­cause a lu­nar month av­er­ages about 29.53 days, the ex­tra days ac­cu­mu­lated through­out the year even­tu­ally re­sult in 13 full moons in a year.

The mag­a­zine def­i­ni­tion was a mis­in­ter­pre­ta­tion of the Maine Farm­ers’ Al­manac, which be­gan list­ing the dates of forth­com­ing blue moons in 1819 and was the ori­gin of the phrase “once in a blue moon.”

The al­manac had de­fined a blue moon as the third full moon in a three-month sea­son that has four moons rather than the usual three, Chang said.

Un­der this old for­mula, the next blue moon will come in 2016.

“Re­gard­less of its ori­gin, a blue moon is worth watch­ing be­cause of its unique tim­ing,” she said, adding that the ce­les­tial event last oc­curred in Au­gust 2012 and will not oc­cur again un­til Jan­uary 2018.


A rare “blue moon” is seen yesterday evening in the sky above Taipei.

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