Two planets orbit closer to the sun than Earth does. One of them is the brightest of all planets and can appear as many as 4 hours after the sun sets. The other world can rarely be seen more than about 1½ hours after the sun sets and is therefore the most elusive of the planets.
The first is Venus, and the second is Mercury. And this week is not just the time this year when elusive Mercury is highest after sunset, it is also the week when Mercury's fellow planet Venus blazes brilliantly just to the upper left of Mercury, guiding our way to it.
Finding Mercury via Venus: On any clear night this week and weekend, all you have to do is make sure you have an unblocked view to pretty low in the west where the sun went down. By about a half-hour after sunset, you should be able to see Venus shining with great luster.
Between about 30 and 45 minutes after sunset, you should first spot a much lesser light beginning to burn into view to the lower right of Venus. At that point, you are seeing what even some veteran skywatchers have never beheld: the swift little planet Mercury.
A close pairing: Although many millions of miles will separate them in space, how close in the sky will Mercury be to Venus? Rather close. If you extend your thumb out at arm's length, Mercury will be no more than about two thumb-widths from Venus for about the next seven days. That's close enough for you to fit the two planets together easily into the field of view of most binoculars.
The quasi-conjunction of Mercury and Venus: In this column, I often speak about celestial events called conjunctions and say that they are meetings of two objects in the heavens. Technically, however, a conjunction is when one object is passing due north or due south of the other. No such passage occurs in this current pairing of Mercury and Venus. Such an event - when one celestial object pulls to within 5 degrees (about half the width of your fist at arm's length) of another without ever passing - is rather rare. It has been called a quasi-conjunction. And this current one of Mercury and Venus is the first quasi-conjunction between bright planets since 2006.
Enjoy them while you can: Mercury and Venus are closest together in the sky this Sunday and will remain at that distance from each other for quite a few days.
One thing to note, however, is that Mercury will be getting dimmer with each passing day. Why? Because as the planet comes around this side of its orbit toward us, it will show more and more of its night side to us. Mercury, like our moon, has phases. A good telescope will reveal that Mercury is undergoing one and is getting thinner and thinner as we progress into April. By the middle of April, even binoculars may not help you get a glimpse of Mercury.
Fred Schaaf is a local author and astronomer. He can be reached at: