THE PLANETS IN MAY
I Written for "The Press’* by K. W. BOTH] The most important astronomical event of the month is the transit of Mercury over the sun’s disc on May 6. It was for the purpose of observing a similar event, the transit of Venus in 1769, that a British expedition under Captain Cook sailed into the South Pacific and on this occasion rediscovered New Zealand. The precise timing of either Mercury’s or Venus’s passage in front of the sun affords a reasonably accurate method of determining the distance of the earth from the sun, the so-called astronomical unit of distance, which is the basis of all distance-calcula-tions in astronomy. Weather permitting, the coming transit should be easily observable with the aid of good fieldglasses or a telescope. It is absolutely necessary, however, to protect the eyes from direct sunlight by means of a uniformly blackened screen. Such a screen is easily made from a piece of photographic film. As the apparent diameter of Mercury is only the one hundred and fiftieth part of the solar diameter, it is too small to be seen without optical magnification. The transit begins shortly after noon and lasts two hours 21 minutes. Mercury passing near the lower (northern) rim of the sun. Glimpses of the red planet Mars ; may still be caught near the northwestern horizon at nightfall. Mars sets about two and a half hours after the sun.
Jupiter, the largest of the planets, dominates the night sky as the brightest star. It is true north about 9.25 p.m., 8.25 p.m., and 7.25 p.m., at the beginning, middle and end of the month, respectively. Because of its brightness and prominent position .it catches the eye of the casual observer. With its four major moons and its cloudy surface it is always an excellent object for telescopic observation. Saturn, the other giant, is also coming into favourable position. It is the brightest star in the east after dark. By the end of the month it already rises shortly after sunset, about 30 degrees south of due east. Saturn is also superbly suited for telescopic observation, once it is sufficiently high above the horizon and clear of the ground haze. The unique feature of Saturn is its ringsystem. To us the rings appear to have continuous surfaces; in fact they are not rigid discs but a rather loose conglomeration of small-sized pebbles and ammonia snowflakes held in their orbits round Saturn by virtue of their revolution. On the evening of May 15 the nearly full moon passes very close below Saturn. Within an hour the moon shifts its position by as much as its diameter.
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Press, Volume XCV, Issue 28265, 1 May 1957, Page 18
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443THE PLANETS IN MAY Press, Volume XCV, Issue 28265, 1 May 1957, Page 18
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