A good month to see the plan­ets in our night sky

The Timaru Herald - - COMMENT&OPINION -

In spite of, or per­haps be­cause of, the crazy stormy weather ear­lier in April, I had a cou­ple of nights of un­usu­ally crisp and clear sky. On the 6th I was lucky and got to see Mars and Saturn while they were still close to­gether. I hope you were able to spot them dur­ing the con­junc­tion of the pair.

Then the power to the street­lights in my neigh­bour­hood was out for sev­eral days (strangely but hap­pily only the street­lights were af­fected). This ad­di­tional level of dark­ness made for ex­cel­lent view­ing of the Large and Small Mag­el­lanic Clouds as well our own Milky Way. The so­called ‘Clouds’ of Mag­el­lan are ac­tu­ally small and nearby gal­ax­ies that ap­pear to be two faint white smudges of or­di­nary cloud adrift in the night sky. Closer ex­am­i­na­tion, how­ever, will re­veal that they don’t change shape, or grow, or dis­si­pate and float away as clouds usu­ally do.

But they do move. They ad­vance ever so slowly around the South Ce­les­tial Pole (SCP), com­plet­ing a full cir­cle once ev­ery 23 hours and 56 min­utes. The SCP is the point in the sky di­rectly above the south pole of Earth. This is dif­fer­ent from the mag­netic South Pole. Vi­su­alise the axis on which Earth spins as a real pole that ex­tends north and south into the sky. The pole points true north and true south. Ce­les­tial ob­jects near the poles ap­pear to re­volve around the poles as Earth ro­tates daily on its axis.

If you want to check this out, go out­side and find the South­ern Cross. Note its po­si­tion and ori­en­ta­tion rel­a­tive to a fixed ob­ject - a chim­ney or cor­ner of the house or a tree, etc. Then wait a cou­ple of hours and go out again. Stand in the same spot and, if the sky is still clear, you will see that the Cross has moved higher and a lit­tle right of its pre­vi­ous po­si­tion. It moves clock­wise around the SCP.

If the sky is very dark at your lo­ca­tion then while you were ob­serv­ing the mo­tion of the Cross, you may have no­ticed the Clouds of Mag­el­lan be­low and to the right, or at least the large one, since they lie in­side the cir­cle the Cross makes around the SCP. The South­ern Cross and the Large and Small Clouds of Mag­el­lan are vis­i­ble all year round at Ti­maru’s lat­i­tude, which is close to mid­way between the Equa­tor and the South Pole.

New Moon in May will be on the 15th. Haratua, the 12th month of the Maori lu­nar cal­en­dar, will be­gin at sunset the fol­low­ing day. The Moon will be full around 2am on the 30th so be sure to look for it on Tues­day night, the 29th.

The large but wan­ing Moon will not rise un­til af­ter 8:30pm on the 4th, and later each night af­ter, so the dark­est nights for evening stargaz­ing will be the two weeks fol­low­ing.

Through mid-month Mercury will still be vis­i­ble as a ‘morn­ing star’ in the east be­fore sun­rise. Venus will be vis­i­ble above the west­ern hori­zon dur­ing the end of twi­light this month. I saw it last evening around 6:30, bright in the fad­ing sunset. It was my first sight­ing of the Evening ‘Star’ this year, which is al­ways spe­cial as I rarely see it in the morn­ing sky. It will ap­pear more bril­liant as the year pro­gresses and it sets later in a darker night sky.

Jupiter has been ris­ing ear­lier and ear­lier and will be up in the east be­fore sunset this month, start­ing its evening west­ward jour­ney across the sky. You may find it shin­ing brightly in the op­po­site side of the dark­en­ing sky from Venus. On the 9th we will pass Jupiter in our faster in­ner or­bit around the Sun. Earth will be between the Sun and Jupiter, and Jupiter will be said to be ‘‘in op­po­si­tion’’.

Mean­while Saturn will rise in the east around 9pm on the 1st, fol­lowed an hour later by or­ange-tinged Mars. By the end of the month Saturn will be up by 7pm and Mars will fol­low two hours later. When our up­per at­mos­phere is not un­duly per­turbed, the two plan­ets may catch your eye and stand out from the stars around them be­cause they will shine with a more con­stant light. Stars will tend to twin­kle.

Venus is brighter than Jupiter, and Jupiter is brighter than the bright­est star. Mid-month at around 8pm, if you stand fac­ing north and look to your left (west) you will see Jupiter mid­way above the hori­zon. Look to your right (east) and Sir­ius, the bright­est star in our night sky, will be mid­way above the hori­zon. Sir­ius is 8.6 light years (8.6 times 9,500,000,000,000 kilo­me­tres) away from us and is around 25 times brighter than the Sun.

If you have any ques­tions, would like to re­ceive or share in­for­ma­tion, or just share a stargaz­ing ex­pe­ri­ence or thought, please email me at night­skysouth@gmail.com. Clear night skies, Freidl Hale

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