Starry Skies Above Santa Monica

February 13-20, 2002

Mirek Plavec
Emeritus Professor of Astronomy,
UCLA

   The Sun – A Bit Friendlier to Us
   On Sunday, February 17, the Sun will rise at 6:36 a.m., and set at 5:39 p.m. Compared to the preceding Sunday, we gain 7 minutes of daylight in the morning, and 7 minutes in the evening. And here comes another less relevant 7 minutes. The Sun culminates above the south 7 minutes after our clocks show 12 noon. Last stars disappear in the glow of the sky by about 5:40 a.m., and the brightest stars become visible around 6:30 p.m.
   The Sun is now moving in front of the stars of Aquarius (the Water Bearer), and is still well below the celestial equator, by almost 12 degrees. Thus it passes right overhead, (actually already a little bit north), at the local noon, over Lima in Peru.

   The Moon Visits the Planets
   The Moon was New in the morning of February 12. After that, it will soon begin to adorn our evening sky as a brilliant crescent above the western horizon. It will grow and move eastward every subsequent evening, and will reach its First Quarter in the morning of February 20, Wednesday.
   During this trip, the Moon will be moving somewhat below the ecliptic (the trajectory along which the Sun travels), and so it happens that, in addition to Aquarius, Pisces, Aries, and Taurus, the Moon also skirmishes the huge constellation of Cetus (the Whale). On the evening of February 16, the Moon will pass below the planet Mars.
   A fairly rare event will occur on February 20, Wednesday. The Moon will pass in front of the planet Saturn, and will therefore occult it. Unfortunately for us, this event occurs during the daylight. Saturn will disappear behind the dark edge of the Moon at 3:21 p.m., and emerge from behind the illuminated edge at 3:56. The situation is not hopeless, however, for observers. The Sun will be already fairly low in the sky (sinking, during the event, from 26 to 20 degrees above the western horizon). If the sky is cloudless, the Moon should be easy to spot, high in the east, and if you use binoculars or a small (even terrestrial) telescope, you should see Saturn without much difficulty.

   Two Planets Close to the Sun: Mercury and Venus
   Mercury will still precede the Sun in the morning, rising about 80 minutes before the Sun on Sunday morning. However, this is not a good apparition, Mercury is deep in the southeast, and not bright enough to be seen easily in the brightening morning sky. There will be a much better chance to spot this fast runner in the evening sky in April and May.
   Venus is very bright, setting after the Sun in the early evening, but is located, in space, still almost behind the Sun from our point of view. On Sunday, Venus will set by 6:16 p.m., which is 37 minutes after the Sun -– too close for comfort. However, Venus is so bright that it may be possible to spot it low above the south-western horizon some minutes after sunset. You would have to watch the sunset above the ocean and the sky above the horizon must be very transparent.

   The Other Three Evening Planets
   …are much easier to see, and the Moon will be helpful, as I noted above. Mars, in the constellation of Pisces (the Fishes), is visible above the western horizon, and sets before 10 p.m. Mars is now quite far from the Earth, therefore fading, and shines now just as a very ordinary star of the first magnitude. However, it does dominate the western sky in the early evening, because there is no brighter star there. On the evening of February 16, the Moon will help you to identify Mars.
   Saturn probably also requires help to identify, since it is also not brighter than an ordinary star of the first magnitude. The reddish star Aldebaran in Taurus comes to your assistance. The two, Saturn and Aldebaran, form a fairly close and therefore rather distinct pair. They are quite high above the south ( “almost overhead”) when the sky gets sufficiently dark after sunset, and then move to the western sky and set after 1 a.m.
   Contrary to Saturn, Jupiter poses no problem. It is simply the brightest “star” in the evening sky. It passes the meridian very high above the south at 8:30 p.m., and then shines above the west Jupiter is projected into Gemini, to the east of Saturn.
   The only real star that can compete with Jupiter in brightness is Sirius, located much farther down in the southeast, if you look early. Sirius culminates above the south around 9 p.m., and after that, it is visible in the south-west for most of the night.

   The Early Evening Sky…
   say at 7 or 8 p.m., is truly beautiful! Jupiter and Sirius dominate, between them lies the beautiful constellation of Orion, and first magnitude stars are more abundant now than at any other time of the year.
   I think that the bright star, Procyon, in the constellation of the Little Dog, deserves a few words. Procyon shines to the east of Orion, and also to the east of the line connecting Sirius and Jupiter. Its name means “preceding dog star,” since it rises before the real “dog star,” Sirius. Somehow, Procyon is indeed secondary to Sirius. Sirius emits as much radiation as 22 of our Suns, Procyon only as much as 6. Its radius is twice the radius of the Sun, which makes its surface area 4 times larger, and if it had the same surface temperature as our Sun, it would radiate only as much as 4 Suns. Procyon, however, is a bit hotter, by about 700 degrees, and that explains its somewhat higher luminosity. It appears quite bright to us, since it is relatively close, 11 light years. And it competes with Sirius also in that it has another “Pup” – a degenerate white dwarf, like Sirius. However, everything is smaller with this Little Doggie Star: while it is not too difficult to see the Pup of Sirius at suitable times, Procyon’s companion is much more difficult as it is 15,000 tumes fainter than Procyon. It is probably only twice as large as our Earth, but extremely compact.