As part of a continuing effort to get a blog centered on history and related topics started, I've been writing some sample posts to try to figure out exactly how I want to approach the new blog.
I started out with the idea that it would be a simple "On this day..." sort of exercise, but I've pretty much decided that the approach is a) too limiting of what I'm aiming to do and b) way too overdone. I'd like to remain open to doing that sort of entry on a regular but not constant basis, but I want it to be more, as well. So, the blog is not ready to go live yet. On the other hand, I've had some interesting experiences in reading and writing the sample posts.
For example, I that today is the fifth anniversary of the demotion of Pluto from planet to dwarf planet. I thought that would be an interesting event to note, and decided to take a quick look to see if I could find out about the story behind the event. What ensued was two-and-a-half or three hours really interesting (to me, anyway) research and the writing of a blog post summarizing what I'd learned.
I had fun with it. I don't want it to go to waste, but since the new blog is not ready to unleash on the world just yet, I thought I'd share it here.
And so, this is what I learned about Pluto, dwarf planets and the International Astronomical Union:
One of the things I most love about history, and about historical events, is that it is possible to start with one event and end up roaming around in any subject area imaginable.
Take the redefinition of the term "planet". On August 24, 2006, the International Astronomical Union (IAU), which is the internationally recognized body given the authority to assign designations to astronomical bodies, redefined - or rather, created an official definition of - the term. Apparently, there hadn't been an official definition previous to this time. By codifing a definion, they read Pluto out of the nine planets of our solar system and into the newly designated classification of "dwarf planet".
I intended to take a quick look to see exactly what that definition was, how a planet differs from a dwarf planet, and why they (perhaps that should be "they") decided that Pluto was not one but the other. It should have taken fifteen or twenty minutes, tops, not least because the Internet is a wonderful thing.
Right? Well, not really. I learned in the course of a couple of hours of research that the redefinition is not as universally accepted as the IAU would have the world think. I also found out some things about the outer reaches of the solar system that are just amazing, and that the picture of that part of our galactic neighborhood is much different from that I learned about as a child entranced by the very idea of outer space.
To begin with, while it seems at first glance as if the category of dwarf planet was engineered mostly to have something to call Pluto once it was removed from the list of planets, it turns out that there are other objects in the category, and that Pluto isn't even the most massive of the four largest of its new kind. It turns out that there are a lot of things and a lot more complexity than was thought to the region beyond Neptune, now the outermost planet since the demotion of Pluto, and that small planet-like objects in that region are called Trans-Neptunian objects. There are, according to some sources, up to 1,200 of these objects. I also discovered that this region beyond Neptune is made up of three areas, which overlap to at least a certain degree.
There is the Kuiper belt, which is similar to the asteroid belt between Mars and Jupiter but twenty times as wide and twenty to two hundred times as massive as the asteroid belt. It extends from the orbit of Neptune to about 55 astronomical units (AU). An astronomical unit, in case you missed science class that day, is the rough distance between the Earth and the Sun, more or less 93 million miles. Then there is the scattered disc, which overlaps and lies beyond the Kuiper belt, which stretches from around 30 to 35 AU from the Sun to well beyond 100 AU from the Sun and reaches well above and well below the plane of the ecliptic, the plane on which the planets orbit around the Sun.
Beyond the scattered disc is the Oort Cloud, which is still a hypothetical construct since there have been no confirmed direct observations of it. The Oort cloud probably reaches out to around 50,000 AU from the Sun, nearly a light year out and almost a quarter of the way to Proxima Centauri, the closest star to the Sun, although some estimates put its outer edge as far as 100,000 to 200,000 AU out. That's a very long way. The objects in the Oort cloud are only loosely bound to the solar system and can be affected by the gravitational influence of passing stars and of the galaxy itself. The objects in this region are mostly icy and likely came into being much nearer the Sun but were scattered by gravitational interaction with the outer, giant planets. It is believed that most long-period comets originate in either the scattered disc or the Oort Cloud.
All of which is very interesting, but I set out to find out about Pluto and why it is no longer considered a planet. Pluto was discovered, officially speaking, on February 18, 1930 by Clyde Tombaugh, from images taken on January 23 and January 29, 1930 at the Lowell Observatory in Flagstaff, Arizona, although it had been seen in other astronomical images at least sixteen times previously, beginning in 1909 at Yerkes Observatory. It was named for the Greek god of the underworld on March 24, 1930.
Because Pluto is so far away, coming as close as just less than 30 AU but going as far away as just less than 49 AU from the Sun, it is difficult to study. It is known that Pluto has four satellites that orbit very near the planet. In fact, its largest moon, Charon, is so large and close (the two are only 12,200 miles apart, less than the distance between London, in the UK, and Sydney, Australia), that the two have been described as a dwarf double planet. Pluto's diameter is about 66 percent that of Earth's Moon and it has a thin atmosphere of nitrogen, methane and carbon monoxide. Some fuzzy photos of Pluto have been taken by the Hubble Space Telescope, but astronomers will have to wait for a clearer view when NASA's New Horzons mission, which was launched on January 19, 2006, makes its closest approach on July 14, 2015. As an intereting aside, some of discoverer Clyde Tombaugh's ashes are aboard the New Horizon probe.
Again, all very interesting. Still, the point, spurred by the notation of the IAU's new definition of "planet" on this day five years ago, was to find out why Pluto is no longer considered a planet. Well, here's the thing. A resolution by the IAU said that in order to be a planet, an astronomical body must be in orbit around the Sun (or, I assume, a sun). It must be massive enough to be a sphere by its own gravitational force. And, it must have cleared the neighborhood around its orbit of other interplanetary debris. The third item in the definition is the sticking point where Pluto is concerned. It is slightly more complicated than that, but this is a history blog, not a science blog, all appearences to the contrary today.
As I mentioned up-post, at the same time that the IAU created its new definition of a planet, it also created a definition of dwarf planets, which is essentially the same thing as a planet, except that a dwarf planet has not cleared the neighborhood around its orbit of debris. And so that is what Pluto is considered to be now, a dwarf planet. This despite the fact that another of the four largest dwarf planets in the solar system, Haumea, which was named for the Hawaiian goddess of childbirth, is not spherical (item number one of the definition of a planet or a dwarf planet), but is shapred more like an American football. Which leads me to believe, if I might be allowed an opinion, that there is something wrong with the definitions.
Apparently, not even everyone in the astronomical community agrees that Pluto is not a planet. After a conference at Johns Hopkins University on August 14 - 16, 2008, a report was released stating that scientists could not come to a consensus regarding the definition of a planet. Well, they get to have an opinion, even if you and I don't, but there was also a certain amount of controversy among the public when Pluto was read out of the list of planets. I know, when I heard about it, my reaction was something like, "Hey, wait a minute..." And if asked how many planets there are, I still automatically answer, "Nine."
So, you see, you can attempt to find out about one particular event in history and end up learning about astronomy. Or geology, or mathematics, or biology, or politics, or construction, or business. Or, really, anything. And that is a good thing, I think. Certainly, I learned a few things I didn't know as I researched today's post.
I promise, this blog won't turn into Your Daily Science Lesson. But some things are just too interesting not to follow up on.