Starry Skies Above Santa Monica

June 6-13, 2000

Mirek Plavec
Emeritus Professor of Astronomy, 
UCLA

   Mars Is The King
   Yes, Mars should now dominate our night sky -– unfortunately, like so many medieval monarchs, it is rather inaccessible, and we may say that, to us Californians, it behaves in rather a nasty way. Certainly, if I had the talents of Thomas Jefferson, I could draft another document full of complaints -– this time against Mars.
   Let’s start with dry facts: On June 13, Mars will reach its opposition to the Sun, that is, it will stand just opposite to the Sun in the sky, and shine all the night. Here comes the first “however”: these June nights are the shortest nights of the year, so Mars’ domination is not that long. To take a specific example, let’s consider the night of Saturday, June 9/10, very close to the opposition date (the time differences between June 10 and 13 are insignificant). The Sun will set, at a point way to the north from the western point of the horizon, at 8:04 p.m. At that time, Mars should emerge on the opposite side of the sky, in the south-east. Here is the first of the unfriendly acts of Mars: while for us, living close to the ocean, the sunset is not difficult to watch, Mars emerges on the opposite side of the sky, behind all the city lights and hills and smog.
   To add insult to injury, Mars is not located EXACTLY opposite to the Sun. If it were, it would rise at the point where the Sun rises shortly before Christmas. In the noble astronomical parlance: on June 21, at the time of the summer solstice, the Sun will be farthest north from the equator, namely 23 degrees and 26 minutes. On June 13, at the time of the opposition of Mars, the Sun will already be very close to this goal: namely, at 23 degrees 14 minutes. Therefore, Mars, being in opposition to the Sun, should be located at minus 23 degrees 14 minutes. Instead, Mars is more than 3 degrees (6 apparent diameters of the Moon) to the south of that point. As a consequence, while the Sun will set at 8:04 p.m., Mars will emerge 22 minutes later (and behind all the obstacles I mentioned above). And, in the morning, before the Sun rises at 5:41 a.m., Mars will disappear in the waves of the ocean already by 5:32. These differences are caused by the fact that the plane of Mars’ orbit about the Sun does not exactly coincide with the plane of the Earth’s orbit, but is tilted to it by almost 2 degrees.
   The orbit of Mars differs not only in its inclination, it is significantly more eccentric than the orbit of the Earth -– that is, one recognizes more easily that it is an ellipse. At this year’s opposition, Mars is near that point in its orbit where it is nearest to the Sun, and therefore also to the Earth. As a consequence, Mars is becoming brighter and more magnificent than it has been for the past 13 years! Its brightness exceeds that of Jupiter, so only Venus is brighter. And the apparent size of the disk of Mars, as seen in a telescope, is unusually large – if even an ardent amateur astronomer is willing to call 20 seconds of arc “large!” 
   Again, because of the eccentricity of its orbit, Mars will not be really closest to us until June 21 – again, if you are willing to consider a distance of 67 million kilometers (42 million miles) “close!” Well, we must accept things as they are – Mars simply won’t come closer and appear larger in the telescope! After all, we, here in southern California, are not so badly treated! When Mars culminates, around 1 a.m., it is located 30 degrees above the southern horizon. This is not so bad! You may be able to glimpse Mars during the night, perhaps above your neighbor’s roof. I would strongly recommend at least one short night trip to the ocean shore — the “tiger-hued,” very bright planet is worth seeing – its high brightness and striking appearance do not come often! 

   Venus Is The Morning Queen
   As mentioned above, there is only one planet that beats Mars in brightness, and this is Venus. On Sunday morning, June 10, Venus will rise by 3:16 a.m., while the Sun rises at 5:41. Early risers, or anyone among you who happens to get up around 4 - 5 in the morning, don’t forget to look towards the east! Venus is really quite brilliant above the eastern horizon, in the constellation of Aries (the Ram). 
   Since I complained about Mars, it is probably proper to complain a little bit about Venus, too, to show you that I am impartial. (After all, some queens were really no better than the kings…) On June 8, Venus reaches its greatest elongation from the Sun: it will be full 46 degrees to the west of the Sun. That’s a lot. However, Venus is projected into the constellation of Aries, located 11 degrees above the celestial equator – but this is, at the present, not a favorable position, since the Sun is 12 degrees higher to the north. Therefore Venus rises relatively late, only two and half hours before the Sun. In a more favorable position, Venus could be rising full four hours before the Sun. Still, the morning Venus is relatively easy to see, if only…you know, early risers are rewarded! 

   The Early June Late Moon
   On June 6, at the beginning of our special “SMM week,” the Moon is (was?) very nearly Full, and shining just a bit to the north-west of Mars. That’s natural, since Mars is very near its opposition to the Sun, and at Full Moon, the Moon is in opposition to the Sun! After that night, the Moon will slowly lose part of its bright face, and recede into the night, passing from Sagittarius through Capricorn into Aquarius. The Last Quarter comes on the night of June 13/14: on that night, you will see just one half of the Moon’s face illuminated, but you must wait for its rising, which comes well after midnight.