GLORY OF THE STARS

New Zealand Herald, Volume LXX, Issue 21506, 1 June 1933, Page 8

GLORY OF THE STARS

MOTIONS OF PLANETS MARS. AND JUPITER; PHENOMENA IN JUNE BY CEi:rX ATJSIITRALIS That all the planeta hare a motion of their own, independent of the motion of the celestial vault which forms the background, has been recognised since the earliest times, as is evidenced by their name, which is derived from the Gr<iek "planetes," a wanderer. Both the inferior planets, Mercury sind Venus, beiag at all times within the Earth's orljjt, apparently move, with a pendulum-like swing from side (o sile of the Sun, being seen alternately in the morning and evening •ikies. Thi:s motion must have been puzzling tc the ancients, especially in the <:aj>(s of Mercury, which lies generally very close indeed to the Sun's apparent pis.ce iin the sky. An indicaticn of the doubt which arose in their mindit is revealed by the i'act that. Venus was given tvro names—Phosphorus. or Lucifer as; the morning* star and Hesperus as the evening star. Merc ury, lying ciosier to the Sun than Venis, swings more quickly, remaining oei each side for two months, while Venus remains for 10 months. The period of visibility oi: each is less, of comse., since the planets are lost to vievr when near tho Sun. Mars, Jupitei and Saturn The other three planets which are visible to the naked eye, being outside the Earth's orbit, can be seen at any angular distß.nce from the Sun. They are at their brightest, and nearest to tl:.e Earth, when directly opjx>- ' site to the Sun, then being due north at midnight and remaining above the horizon tor the longest period. Mars comes to opposition every t'*o years an I tv'O mo nths. It makes a complete circuit of the zodiac between opiKjfsitions. Jupiter comes r.o opposition every 13 months. Unlike Mars, it takes 12 years to go round the zotlia,c completely. Saturn.,. the moss distant planet known to the ancients, requires nearly 30 years to complete a circuit ol : the zodiac, while its oppositions take place at intervals of a year and 12 days.

There -is a peculiarity in the motions of the three superior planets wh-.-n n<ear opposition. For the greater part of the time between oppositions they fixe moving through the; sky in the same direction as that followed by the Sun and Moon, tout juisfc before opposition they stand s;till and then move backward, retracing some of the ground they ha*e just traversed. After opposition the planets once more stand still and then resume their -forward movement. This was what 3lilton ha.d in mind when he spoke of— Their 'Pandering course, now high, flow lojt, then hid. Progressive, retrograde and standing etjll. Motions ol Mairs and Jupiter Ali this year this phenomenon of planetary motion has been unfolding in the skies; in the constellation Leo, in the north-west sky these nights, where Mars ard Jupiter have been playing a celestial game of ihide and seek. In Jannarv the two planets lay east of the bng;ht, fixed .star, Regulus. Mars was jusi; ending its forward while Jupiter was already retrograding. A t <:he end of that month the two were at their nearest, Man; then being considerably north of its companion. Mars, bjiiig nearer to mi, moves apparently more swiftly and covers a greater arc than Jupiter, which slowly retrograded until 3lay, when it reached its stationary point and. then began to retrace its coarse, having covered 10 degrees of arc: in its backward motion. Mars, in the meantime, had rapidly retTOgi'Uded over an arc of nearly 20 degrees bv the beginning of April, uhich brought it only four degrees! east of Regulus. Makmg a graceful loop in the sky it recommenced its forward journey, rapidly overhauling its more filowly moving companion. The loop it had performed, however, brought its path, -s-hicli formerly lay three degrees north of Jupiter':.'., almost in line, with the latter's movement. The consequence snll bo that when Mars has made up all the: ground it lost in its retrograde sweep and draws level with Jupiter, which will occur on June 5, the distance separating the two planets trill be only a-tent'i of the former separation, 0.3 degrees. Thereafter Mars will craw steadily ahead of its brighter companion, and by r ihe end. ot the raonta it will be five degrees in the lead. Positions of Planets The Sun. will foe in the constellation Taurus until June 21, when it wi enter Gemini. The shortest day will occur on the 22nd. The Moon will b<s in conjunction with the various planets durinj; the month as follows: Mara and Jupiter, on the morning of Juno 2. The proximity of the three objects this evening will be striking. Saturn, 12th; Veiuis and Mercury, 25th; I tor, 29th; Mars, 30th. Faint stars will ba occulted by the Moon On the follow- ! iing dates: —Juno 4, 6, 10, 13 and 2SThe bright star Alpha Scorpn will oa occulted on the morning Q.f June », disappearing behind the Meon at 4.01 i a.m. and again at 5.40 a.m. , Mercury and Venus are both evening stars during June and will be in mutual conjunction on June 9. Mars and Jupi* tor, as already described, are close iO ,;;ach other in the star group ol Leobeing in conjunction with each other to-diy. Saturn, in Ophiuchus, is slowly acquiring more prominence in the evening sky.