Starry Skies Above Santa Monica

May 16-23, 2000

Mirek Plavec
Emeritus Professor of Astronomy, 
UCLA

   Mercury Replaces Saturn — Temporarily
   For many weeks, we had the opportunity to see the two biggest planets, Jupiter and Saturn, comfortably in the early evening hours, above the western horizon. Together with them there were there the reddish star Aldebaran and the famous star cluster of the Pleiades. The show is now quickly coming to an end.
   Saturn was the first to disappear. On May 25, the Sun will catch up with the planet -– only as seen by us, of course. To speak more astronomically, the two objects will be projected into the same direction; or to speak even more astronomically, Saturn will be in conjunction with the Sun. Saturn will be well behind the Sun, ten times farther from us than the Sun is. Together with Saturn, the Pleiades and Aldebaran will be invisible, so only Jupiter remains above the western horizon. Its time of conjunction with the Sun will come on June 14. At the present, you can still spot Jupiter above the western horizon, if you look early in the evening. To give you a more precise picture, let us consider the situation on Sunday evening, May 20. The Sun will set by 7:51 p.m., and the western sky will remain too bright for at least 40 minutes. Thus the time to search for Jupiter may come about 8:30 p.m. By that time, the upper part of Orion will be disappearing, but Jupiter will still be visible, low above the spot where the Sun has disappeared. Jupiter will set shortly after 9 p.m.
   As a temporary replacement for Saturn, the western sky offers Mercury. The best time to find Mercury is already past, but there is still some chance to spot it. On Wednesday evening, May 16, Mercury will be quite close and just above (to the north of) Jupiter. Jupiter can help you tremendously in identifying Mercury, which by that time will still shine as a bright first-magnitude star. After this conjunction with Jupiter, Mercury will still appear to be running away from the Sun, but only till May 21, when it reaches its greatest eastern elongation from the Sun. Thus on Sunday evening, May 20, Mercury will be projected 22 degrees east of the Sun, several degrees eastward of Jupiter. As mentioned above, Jupiter will set by 9:13, and Mercury will follow half an hour later. However, Mercury will be significantly fainter than Jupiter, but will still shine as a bright star, for example Beteigeuze in Orion, which will be at about the same altitude above the horizon, but farther to the south.
   Shortly after May 20, Mercury will become almost hopeless: it will be fading rapidly and returning back to the Sun.

   Sun, Moon, and The Other Planets
   On Sunday, May 20, the Sun will already be 20 degrees above the equator, and, at the respective times of the local noon, it will be passing just through the zenith at such diverse places as Hilo in Hawaii and Guantanamo in Cuba. For us, the Sun will rise at 5:48 a.m. and set by 7:51 p.m. That’s a total of 14 hours 3 minutes of sunshine per day, but, as is typical for this time of year here at the seashore, fog will probably prevent us from seeing much of the Sun during the day and much of the stars at night. The Sun will be passing below the Pleiades in Taurus, the Bull.
   The Moon was in its Last Quarter on May 15, and will be New on May 22. Thus, until about May 20, the Moon will be visible as a shrinking crescent in the south-eastern morning sky, passing from Aquarius to Aries. On Saturday morning, May 19, a very thin crescent will just be passing below Venus. Venus will rise already by 3:44 a.m., and is quite brilliant. If you get the opportunity these mornings about 4 or 5 a.m., look to the east for Venus!
   With Jupiter and possibly Mercury visible rather shortly after sunset, and Venus shining before sunrise, we have one planet available for most of the night -– Mars. Mars rises fairly early, at 10 p.m., culminates above the south by 3 a.m., and is visible, to the early risers, in the south-west. This planet, always considered to be the carrier of bad things, remains, at least in one respect, faithful to its bad reputation. It is located far south in the sky, 25 degrees below the celestial equator. As a consequence, it never reaches any high altitude in our sky. At best, it comes to an altitude of 31 degrees above the south, and this happens at about 3 a.m. Actually, Mars is even a bit lower in the sky than the Sun can ever be for us. The one positive thing I can say about Mars that it is currently pretty bright, already competing with Jupiter. 
   Mars is now projected close to the main stars of the constellation Sagittarius. The name of the constellation is usually translated as “the Archer,” and, indeed, classical pictures of the constellation show an archer aiming his arrow at – what? At the scorpion in the preceding sign of the zodiac? However, this is only a half of the picture, and actually only a half of the man: the lower half of his body is that – of a horse! Actually what you see is most likely – a teapot, as I will show you soon, when that constellation is easier to see in the evening sky.