Mirek Plavec, Emeritus Professor of Astronomy, UCLA

   The brightest planet, called Venus by ancient Romans, was called different names by other ancient nations (Aphrodite, Astarte, Istar...), but had the same position among their gods: it (she?) was the goddess of love and beauty. Why? Venus is really beautiful and lovely as an evening star when it is shining above the western horizon during the spring months. It is not there every year, but this past spring, Venus has been truly splendid and dominating. This splendor comes quickly to an end, as Venus - curiously - comes closer and closer to the Earth!

   The orbiting of planets around the Sun cannot be considered as a fair race! Venus, as an inner planet, has a shorter orbit, and runs faster than the Earth (35 km/s as against ours 29.8 km/s). Thus the time must inevitably come when Venus catches up with the Earth. When this happens (this year, on August 20), Venus will be located between the Earth and the Sun, and therefore will be invisible in the daytime glare of the Sun. Venus is currently catching up with the Earth, or, from our point of view, closing up to the Sun, so it sets every evening earlier and earlier after sunset: on July 28, by about 9 p.m., and on August 4, by about 8:30 p.m. And, of course, if it is setting for you not into the ocean but behind the Santa Monica Mountains, it will disappear sooner still.

   With respect to the stars, Venus remains close to the first-magnitude star Regulus in Leo. Actually, its normal motion eastwards with respect to the stars is halted, and Venus will move back, i.e. westward, below Regulus. This retrograde motion of planets was a great puzzle for ancient astronomers, who believed that all the planets (as well as the Sun) are orbiting about the Earth. In a report written about 3,500 years ago (!!!) by a Babylonian astronomer to his king, the astronomer announced the following terrible surprise: "When Venus approached the claws of the Scorpion, it was thrown back!" If he lived today (and kept his ideas about the universe), he would have reported similarly, "When Venus approached the front paws of the Lion, it was thrown back! "

   While it will be gradually more difficult to find Venus in the sky, the planet becomes more interesting to look at with a telescope, even with binoculars. For, as it comes nearer to us, its apparent disk grows. Out of this disk, only an even-narrowing crescent is visible as illuminated by the Sun, and you will see no surface details, since Venus prefers to hide behind thick clouds. However, the illuminated crescent is so large that my students once suspected that I was cheating on them and showing them the Moon instead of Venus, in our telescope. . .

   Mars, contrary to Venus, moves leisurely towards the east among the stars, and is currently passing through the constellation Libra (the Scales). This is an inconspicuous constellation, yet I would like to call your attention to its two main stars, since they are worth looking at with binoculars or a small (even terrestrial) telescope. Astronomically speaking, the two stars are of the 3rd magnitude, comparable to the fainter stars in the Big Dipper. They do not have any serious competition on the fairly long segment of the ecliptic between two first-magnitude stars: Spica to the west and Antares, in Scorpius, to the east. Thus they are fairly easy to identify if you can watch them against a tolerably dark sky.

The still fairly bright Mars will be very close, and just below, the star Alpha (or, if you want, Zuben-el-Genubi) during the first decade of August. This star is a double star, and the fainter companion is sufficiently separated to be easily seen in a modest optical instrument. Actually, a sharp eye might see it if the sky is really dark. Above Alpha, somewhat to the north-east, ( and at a distance of about half of that between Alpha and Spica), is Beta (or Zuben-el-Schemali - "the northern claw"), about as bright as Alpha. Don't look for a faint companion of this one; rather, consider its color! It has been often called "the only green star visible to the naked eye".

However, naked eye will not be able to tell you anything about its color. Stars are objects actually so faint, that our eyes are unable to recognize their colors. When there is enough light coming to our eyes, they work as an excellent color TV. However, when the light level drops at night, the eyes switch to a much more sensitive mode, but this one works like a black-and-white TV screen! Thus, only for the brightest stars and planets we can recognize their colors. High above Mars, roughly towards the zenith, is the bright star Arcturus, and I think you will recognize its orange color. Mars has two fairly distant first-magnitude neighbors: to the west, Spica, which will appear to you as white or possibly a bit bluish, and to the east, Antares, which should show a reddish hue.

Stars colors are never very distinct. The reason is that stars emit photons of all colors (albeit not in equal numbers), so that the resulting color is never clean and distinct. Our Sun radiates most strongly in green color, but no one will call our Sun green! Blue and yellow, as well as ñ to a somewhat lesser degree - violet and orange and red photons also come to us in large numbers, and consequently the Sun appears white or a bit yellowish (except when it is near the horizon ñ about that we will talk next time).

When you use binoculars or a telescope, you may assemble enough photons for your eyes to switch to the color-TV mode. As a consequence, you will see more and more star colors. In most cases, they will be rather indistinct, as explained above. Star colors usually become striking only when you observe two stars very close to each other; then, in some binary stars, you may notice a really striking color contrast.

And now, point your telescope or binoculars on Beta Librae ! That star is hotter than the Sun, and should appear simply white even in binoculars. I checked again last evening. In my binoculars, the star is decidedly green! Please check for yourself!