THE PLANET VENUS

Wanganui Chronicle, Volume 90, Issue 118, 23 May 1946, Page 6

THE PLANET VENUS

(By "The Sky Pilot.") “What is the name of that bright st ar in the west early in the evening?” is a question often asked the Sky Pilot and others interested in the sky. And the answer is that it is Venus, the loveliest of the planets viewea with the naked eye, named after Venus, the most beautiful of the ancient goddesses. It is often called the “Evening Star,” and when seen in the morning, before sunrise, the “Morning Star,” because of its commanding brilliance, so captivating and attractive, ever a glorious sighj. to behold. The ancients used to distinguish the two as separate bodies, calling the former Hesperus and the latter Phosphorus. And so Milton has the lines:

“The sun was sunk, and after him the star Of Hesperus whose office is to bring Twilight upon the earth, short arbiter ’Twixt day and night.” —“Paradise Lost.”

But some of the ancients knew it to be the same sta-’. Actually it is not a star at all, but a planet some 67,000.000 miles from the sun, and therefore nearer to the sun than the earth, which is 93,000,000 miles. Taking some 225 days or some seven and a-half months to make its journey around the sun, it covers its journey in about two-thirds the time the earth requires. Venus is often called the “earth’s twin sister” because in size, weight and distance from the sun they are similar. Its surface area is 5 per cent, smaller than the area surface of the earth, and its weight four-fifths that of the earth. When the sun has set and Venus is still above the horizon, it is ar. evening star; but when in front of the sun it sets before it and is then a morning star in that it rises before the sun When the orbit of any planet is inside the earth’s orbit, it is never seen at midnight, as is the case of the planets outside the earth’s orbit, such as Mars, Jupiter, and Saturn, etc. Both Mercury and Venus, therefore, set during the evening well before midnight. These are the planets conspicuous in the twilight or dusk sky and at dawn.

Venus from the earth is always brilliant or bright, but at times very brilliant, depending upon its distance and phase. It has, however, no light of its own, but shines by the reflected light from the sun, reflecting some 60 per cent, of that light against 7 per cent, reflected by the moon and Mercury. This high reflection suggested, as the telescope and spectroscope bears out, that the planet is covered with dense white clouds. These make Venus the third most brilliant object m the sky next to the sun and the moon, and thereby outshining all the other planets and even the brighest stars. At maximum brilliance it shines with a light 13 times more intense than that of the brightest star. The planet is most brilliant some 36 days before and after inferior conjunction (the point where the planet □asses between the earth and the sun, that is nearest to the earth, into the morning sky). Around the time of greatest brilliancy Venus is visible in full daylight, like a tiny star in the blue sky, attracting the attention of iolk, arousing wonder and interest. When high buildings have hidden the glare of the sun it has been particularly outstanding, and groups of people gather to view it. If one knouts where to look for it the planet may easily be seen. The writer has seen it of an afternoon when returning from the city. When the planet is at its brightest astronomers are often besieged by folk anxious to know something of the dazzling star. It is qjuite a thrill endeavouring to ’find it rpom noon on when the powerful light of the sun does not efface it. Since Venus is covered with such dense clouds the planet itself has never been seen. One or two astronomers have held that they have seen it through the dark patches occasionall’ visible in the great thicknesses of white cloud, but this is doubtful. Even the infra-red photography which pierces haze and cloud reveals nothing of the planet below. So when we are looking at Venus we are looking at its cloud-laden surface. “This must consist of water droplets,” according to some, “but the atmosphere above the clouds is extremely dry and hence it is difficult to detect water vapour.” In this respect it is similar to the earth, where water vapour is confined solely to the lower layer of the atmosphere. Carbon dioxide is very abundant, and more so than on the earth, and is probably the predominant constituent. Neither oxygen nor water vapour have been detected. “Venus is, in fact, very much like what the earth was like before life had commenced to develop,” says Sir H. Spencer Jones. He continues by saying that carbon dioxide and the powerful blanketing effect, together with solar radiation stronger than the earth receives, would combine to make the temperature at the surface of Venus considerably higher than that of the earth, somewhere about 100 degrees C (boiling point of water) Hence there would be an absence of life and a lack of vegetation and oxygen. The hot, humid atmosphere would be responsible for the dense clouds. He styles it “a world where life has not yet developed,” its condition being similar to the stage where the earth was hundreds of millions of years ago. There may be expectation of life in the remote future, he continues, when the sun's supply of radiation becomes greatly depleted and the sun cools down. And so there appears to be a considerable green-house effect beneath the cloud layers of the planet.

What, we view, then, seems to be a dense layer of cloud, impenetrable, situated high above the surface of the planet. Our next article will also be on this planet, when a consideration of its phase appearances and transits will be given.