A planetary grouping
Published on Dec 9, 2006 at 12:36 pm.
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Filed under skywatching.
Oh, I am so spaced out! I got distracted by the whole Mars water thing that I forgot to post this! Near the end of the semester, though, it is pretty easy to get me off track. I used to think that I’d be less harried and stressed once I was done being a student, but I think that being a professor is just as draining, if not more so, at the end of the semester as being a student!
So, what did I forget to tell you? Well, tomorrow morning, there is something else to see (maybe) besides the Saturn conjunction/occultation. Sunday morning, there will be a very close grouping of planets. Jupiter, Mercury, and Mars will all be very close together. In fact, they will be so close together that you might be able to get them all in the field of view of a telescope at low power. You could hold your hand out at arm’s length and cover all three with your thumb. Such close groupings happen every now and then. There was a grouping, not as close, just a few years ago, and I remember going out to photograph such a close grouping with a friend about 15 or 16 years ago (we didn’t get the photos bacause her camera was jammed with sand from a trip to the beach a while earlier). This particular grouping is a bit closer than most. Depending upon how you categorize such groupings, it is the closest in about 80 years. But, there are several ways to categorize these things, and using other methods, it is only the closest in about 25 years. But, that doesn’t really matter. All three planets will fit into a circle of 1° diameter. (Note: for my readers in Australia, New Zealand, Japan, and other places on the other side of the International Date Line, this will be Monday morning, December 11.)
So, if you want to see this close grouping, what do you do? Well, I’ve got bad news for you. It will likely be quite difficult to see. All three of these planets are quite far away, on the other side of the Solar System. In fact, they are nearly directly opposite the Sun from us, so they will appear very near the Sun in the Sky. You’ll see them only a half hour before sunrise, as civil twilight is getting the sky bright, particularly in the souteast where the planets will be. In fact, at that time, if you hold your hand at arm’s length with your fist clenched and held horizontal, the planets will only be the heigth of your fist above the horizon. That means that any clouds or haze on the horizon is likely to obstruct your view. Likewise for any hills, buildings, trees, bushes, or about anthing else. And then, the sky itself will be getting bright, washing out the planets. If you do have a clear horizon, you should be able to see Jupiter easily enough. Mercury will be the next easiest to see, just up and perhaps a little to the left of Jupiter (depending where upon Earth you are looking from). Mars will be the tough one. It will be about 1/10 as bright as Mercury and a bit to the right of the Jupiter and Mercury pair. Binoculars might help. However, if you use any optical aid, such as binoculars or telescopes, be VERY careful and mindful of what you are doing. The Sun will rise in almost that same area just a few minutes later, and you DO NOT want to accidently catch the Sun with your binoculars or telescope.
Now, what makes this interesting is that Mercury, Mars, and Jupiter are all moving with respect to one antoher in the sky. Mercury was actually closest to Mars (in conjunction with Mars) this morning. Mercury will be closest to Jupiter (about 1/5 of the apparent diameter of the Moon) Sunday morning, about the time of the closest grouping, and only a few hours after the Saturn event (occultation or conjunction, depending upon where you are observing on Earth). And then Tuesday, Mars and Jupiter will be at their closest. So, there are four conjunctions happening within a four day period of time. Now, THAT is much more rare than having a close grouping of planets.
In fact, it has been speculated that the Star of Bethlehem may have been something like this, rather than a “star” as we use the term today. Back in those days, the term “star” pretty much meant anything in the sky. In fact, planets were thought of as wandering stars (that is what the name “planet” means). That would also explain why others besides the Magi didn’t see it. They may have seen the planets close together, but nor realized the significance of that event, or how rare it might have been. And, simply a grouping of planets wouldn’t have been sufficient, it would have to have been a series of groupings, conjuctions, occultations, etc that would have been rare enough to make the wise men journey all the way to Judea. And the other thing is that, beind skywatchers, they’d have known about such a grouping as this, even if they didn’t see it happening due to clouds or obstructions.
So, for my readers, even if you don’t get to see the close grouping, you, too, know that it is going on.
-Astroprof
