A time of year when the days get rapidly longer

Weekend Argus (Saturday Edition) - - GOODSTUFF -

THE MONTH starts with a wax­ing gib­bous moon that be­comes full on the 4th, with new moon fol­low­ing about two weeks later on the 18th.

The ac­tual time of the new Moon is 8.46pm so the first cres­cent will not be­come vis­i­ble till the evening of the 19th, with the sight­ing mark­ing the start of Eid.

On the 22nd is the spring equinox, Latin for “equal night” – the time when the length of the day is the same as the length of the night.

One might ex­pect that the length of day and night should be equally 12 hours. In­stead, day­light lasts for an ex­tra eight min­utes due to the size of the sun and the bend­ing of light (re­frac­tion): the ac­tual 12-hour day occurred on the 19th.

Some re­gard this as the beginning of spring, while oth­ers say Septem­ber 1 marks the beginning of spring. I won’t en­ter this de­bate, but it is the time of the year when the days are get­ting longer most rapidly in the souther n hemi­sphere. Care­ful ob­servers will also no­tice that the Sun rises to the south of east and sets to the south of west from now on.

How­ever this equinox does mark the end of the south­ern win­ter half of the year, last­ing 186.4 days and the start of the north­ern win­ter-half of the year, last­ing 178.8 days. The colder half of the year lasts about seven-and-a-half days longer for us be­cause the Earth’s or­bit is not cir­cu­lar (but el­lip­ti­cal, slightly egg-shaped) and the Earth trav­els more slowly at this part of its or­bit.

Mer­cury is vis­i­ble just af­ter sun­set un­til the 20th when it sets with the Sun, af­ter which it be­comes a morn­ing ob­ject, ris­ing early in the dawn sky.

Jupiter is well up in the evening sky and sets as the sun rises. The other plan­ets are morn­ing ob­jects: Venus un­mis­tak­ably bright in the east, with Mars vis­i­ble much ear­lier and Saturn ris­ing a lit­tle be­fore dawn.

The evening sky to the west shows the Scor­pion head­ing for the hori­zon, with the red su­per­giant star, Antares, at its heart and set- ting around mid­night.

To the left (south) of Scor­pi­ous, the South­ern Cross and the Point­ers earn their name of Thutlwa, or the “Gi­raffe Stars”, as they graze the tops of the trees: the well­known group of stars is low above the hori­zon.

To the north, the bright star Vega is un­mis­tak­able low above the hori­zon, to the right (east) of which is Deneb, the bright­est star in the con­stel­la­tion of Cygnus, the Swan. On a par with Rigel, it is one of the great stars: 25 times big­ger than the Sun, 60 000 times more luminous and about 1 500 light years away.

The morn­ing sky is truly spec­tac­u­lar, and early ris­ers can en­joy some beau­ti­ful sights. Orion is now well up, with isiL­imela and the Hyades to the left. Sir­ius shines very brightly fur­ther left and forms an equilat­eral tri­an­gle with Betel­geuse (red su­per­giant) and Pro­cyon, the Lit­tle Dog Star.

Cas­tor and Pol­lux can be seen low in the north-east. On the morn­ing of the 10th, a wan­ing gib­bous Moon can be seen close to Limela and by the fol­low­ing morn­ing it will have passed by.

For mid­night owls there is a mi­nor feast. At 1am or later, Orion can be seen ris­ing along with Alde­baran, the red gi­ant star on the small clus­ter of the Hyades to the left. Limela is fur­ther left, and low in the north-east, our twin galaxy, An­dromeda, can be seen. It is the re­motest ob­ject vis­i­ble to the naked eye, 2.3 mil­lion light years away, and a pair of binoc­u­lars will re­veal its shape clearly.

Newspapers in English

Newspapers from South Africa

© PressReader. All rights reserved.