ASTRONOMICAL NOTES FOR OCTOBER

Otago Daily Times, Issue 24417, 1 October 1940, Page 4

ASTRONOMICAL NOTES FOR OCTOBER

Specially Written for the Otago Daily Times Jupiter and Saturn remain close together during this month, the distance between them being reduced to 11 degrees on October 12, when they will be in conjunction for the second time. At their first conjunction in August they were moving eastward, and Juipiter, being the nearer, appeared to be the more rapid traveller, which caused him to pass Saturn at this time. Saturn reached a stationary point on August 27. due. of course, to the fact that the earth was moving directly toward him, and Jupiter was observed under the same conditions on September 4. Since then their movements have been to the westward, and Jupiter, continuing to be the faster of the two, oasses the more distant planet on October 12'. On that day both planets rise together at 8.54 p.m.. and they are a little more than four minutes earlier each successive evening, so that they rise on October 31. at 7.28 p.m., which makes it more convenient for us to observe them in the evenings. When we look at these planets so near together, or when we turn our telescopes upon them, it is well to remember that Saturn is more than twice as far away as Jupiter. Probably most of us find that a natural way of thinking, but another somewhat similar thought should be in our minds when we look at the stars Alpha and D ta Centauri, These stars are commonly known a$ the “Pointers,” and everyone knows that Alpha, the brighter star, is our nearest neighbour, its light taking only a little more than four years to reach us. But Beta is about 25 times as far away as the star apparently beside him. the distance, which is not known with certainty, being something like 110 light-years.

Venus is still a bright object in the morning twilight, where we see her apparently approaching the sun. What is really happening is that she is moving ahead of us in her orbit and preparing to pass round to the other side of the sun. This has the effect that r her distance from the earth on October 1 is 83,000,000 miles, less than that of the sun but it increases to 103.000,000 [ on October 31. ; The constellation which we see due 1 north in the early evening now is Capricornus, The brighter stars group themselves in three lines, making a 1 right-angled triangle. It is beyond all ■ powers of sane imagination to discover how the ancient star-gazers saw any--1 thing resembling a goat in this arrangement, and especially a goat with a fish’s tail instead of hind legs, “'he brightest star, Alpha Capricorni. is a naked-eye double, the distance between the components being about one-tenth of a degree. There is another star, very faint, to be seen only in large telescopes. Sagittarius is still well placed, not far to the west. A group of the brightest stars in the middle of this constellation resemble what is commonly called the “ Plough ” in the northern heavens, but has only two stars instead of three in the handles. The Scorpion is much lower down, and Antares sets a little before midnight. The total eclipse of the sun on October 1 has been mentioned before, in these notes and elsewhere, and the latest news is that several stations on the line of central eclipse will be occupied in South Africa. No observers have made the journey from Europe, but coronagraphs and other instrum6nts have been shipped, and the local observatories will have little difficulty in supplying skilled workers It is a little surprising that no information has come as to observing parties in South America. The line of central eclipse crosses the entire width of Frazil from the sources of the Amazon to the coast near Pernambuco, and the conditions there must be quite as good as on the other side of the Atlantic.

( Here, of course, the total phase occurs • in the morning instead of the atter- ; noon. At the point where the shadow leaves the coast, not far north of Pernambuco, the totality lasts 5 minutes 1 6 seconds, whereas the longest obtainable in South Africa is only 3 minutes 57 seconds. At the position in the middle of the Atlantic where the sun 1 is seen centrally eclipsed at noon, the duration is 5 minutes 35 seconds. On October 1 the sun rises at 6.10 a.m. and sets at 6.46 p.m. These times and all others now quoted are summer time. On October 31 he rises at 5.17 а. and sets at 7.27 p.m. Thus the length of the day from 12 hours 36 minutes to 14 hours 10 minutes during this month. The moon is at first quarter on October 8, and sets on that day at 1.10 a.m. Full moon occurs on Ocober 16. The moon rises on October 16 at 6.50 p.m. and sets on the following morning at б. Last quarter is on October 24, and the moon then rises at 1.5 a.m. The full moon mentioned above just misses the earth’s shadow, but nearly three-quarters of her disc is immersed in the penumbra at 8.1 p.m. on October 16. -