Colliding Planets!
Published on Aug 7, 2006 at 12:14 am.
2 Comments.
Filed under planets, skywatching.
No, this is not a post about Velikovsky!
Of course, now that I’ve mentioned him, I might as well explain for those readers not familiar with the name. Most astronomers and serious amateur astronomers groan at the mention of Velikovsky because we are often bombarded with questions about him. In 1950, Immanuel Velikovsky published a book called Worlds in Collision. The basic premise of the work was that a chunk of Jupiter suddenly just flew out into space, became a comet with a huge tail, flew across the Solar System, narrowly missed Earth, causing massive destruction from its tidal effects, and then settled into orbit around the Sun, forming the planet that we now call Venus. Well, there is a planet named Venus, and there is also a planet named Jupiter. Other than that, there isn’t much right in his work. Velikovsky was not a scientist, but he declared himself to be an expert in the matter. Most astronomers just ignored him, since what he had to say was simply nonsense. Well, that was a mistake. Apparently the literary circles just swooned over his prose, and they bought it. By the time that astronomers realized that people actually believed this stuff, it was too late. By challenging it, that gave all the conspiracy people the idea that he was right. Strange how that works. You see it today. There are a few people out there who have published total nonsense, but if you say so, their followers seem to take that as proof that it is right. I don’t understand that, but I see it over and over again. Anyway, there are a whole host of reasons that Velikovsky’s ideas can’t be right. Still, there are a small number of people who seem enthralled by his ideas, and there even books still be published supporting him (written by non-astronomers, of course). I’ve even seen some of these books in our library!
But, as I said, Velikovsky is not what I was here to write about. If you want to read more about why Velikovsky is wrong, then go here. There have been other, more scientific, suggestions that planets may have collided in the early Solar System. For example, we believe that the Moon was created by a massive impact of a nearly Mars sized object striking the early Earth. But, not even that is what this post is about.
Rather, I wanted to post about planets not colliding, despite my post’s title. There is an urban myth email going around about Mars being spectacular this August 27 (It isn’t: see the post right before this.) But, there will be an interesting planetary event on August 26. As the planets move around the Sun, they never get really close to one another. However, from our vantage point on Earth, they can appear near each other in the sky. The different planets go around the Sun at different speeds, and our view shifts as Earth moves around. The result is that the planets appear to move in the sky against the background stars. In fact, the word “planet” comes from the Greek for wanderer. They appear as wandering stars. Sometimes a planet will be in one constellation, and then some time later it will be in another one. Naturally, they will appear to pass one another now and then. The closet approach as they appear to pass each other in the sky is called a conjunction. There will be a conjunction between Venus and Saturn on August 26. In fact, this will be a very close conjunction. The two planets will appear so close that the apparent distance between them, as seen from an observer on Earth, will look as if it is about about 1/4 the diameter of the Moon! In fact, with Venus being so bright, it will be tough to even see Saturn that close to it! Both planets will be visible in the same field of view through the eyepiece of a telescope. Such a close approach is called an appulse. Actually, I have never heard a real definition of an appulse. It is simply a very close conjunction, but no one seems to agree on how close a conjunction has to be to be an appulse. I rather figure that if the two objects are so close together that it becomes hard to easily see that there are two of them to the naked eye, then it is an appulse. Others think of an appulse as being anytime a conjunction is closer than the diameter of the Full Moon (about 0.5 degrees).
So, the good news is that we are going to have this super close conjunction (appulse). The bad news is that the closest approach will happen at about 23 hours UT. That is 11pm Greenwich Mean Time for all you non-astronomers. At this time, Venus is not even up for those of us in North America. Venus is currently rising in the mornings a bit before the Sun. Venus is not even up yet for Europe at closest approach. For Japan, the Sun has already come up. About the only place on Earth that has a good shot at witnessing this event at its best is central Asia, north of India. For the rest of us, if you go out in the mornings for a few days before hand, you will see Venus getting closer and closer to Saturn. The closest that you’ll see it is early on August 26. But it will still be on the same side of Saturn that it had been. But, on the morning of August 27, you will notice that it is going to be on the other side of Saturn, and for the next few days, if you get up and look, you’ll see it getting farther and farther form Saturn.
So, they won’t collide, and in truth, they won’t even get close to one another. But they will be close together in the sky, and that is a cool thing to go out and observe.
So, go look!
-Astroprof
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