Update: I said that Pluto was demoted in October, but it was in August, so I changed that. Another thing I changed is the size of Pluto to moon, from 1/2 to 2/3. Oh, and I feel like I have to explain eccentrity for those of you who don’t get the pun later on.
Yesterday, the astronomy club I was in talked about Pluto, its history, and the New Horizon, so I thought, hey, why not make a post about Pluto? Besides, two years ago in August, Pluto was taken off its status as a planet, so I guess we should mourn for Pluto.
The story begins around a centruy years ago… nay, around two centuries and a half ago. Around the time United States was being born, an astronomer named William Herschel was doing more astronomical observations than all of living PhD astronomers combined. He looked with his telescope, and recorded his observations meticulously, not knowing that he would discover another body in the Solar System, which was something unimaginable at the time. You have got to realize, these people, since antiquity, thought there were, only five planets other than the Earth. (Ok, depending on the time period, some thought the moon and the sun were planets) At Herschel’s time, Saturn’s distance was estimated to be around 9AU (it goes from 9, its closest, to 10, the farthest), which is a good estimate. So, the solar system was thought to be kind of “small,” back then. Of course, 9AU is humongously large, but small in the context of our current understanding. Then, one day in 1781, by chance, he spotted a blue disk which he dubbed as a comet, since it didn’t seem like a star. He kept observing, but as time passed, though, it didn’t behave anything like a comet. It wasn’t fuzzy, and it kept traveling along the ecliptic, which is the plane that you would see if you wedged a flat plate through the sun’s equator. Comets rarely travel on the ecliptic. So, with further observations, it was found to be a new planet, later named Uranus. Note, others have observed it, but they didn’t realize it was a planet. This discovery doubled the Solar System’s size into 19AU!
(sorry, I love Uranus, and couldn’t resist, look how perfect it looks!)
So, by now, you might be wondering, what does it have to do with Pluto?! Well, just as Yoda says that fear somehow leads to idiocy and cravings for chocolate (oh, wait, it was the dark side, my bad), Uranus leads to other discoveries. You see, Uranus had an anomaly in its orbital pattern. At certain times, Uranus went faster, and at other times, it went slower than expected. There were many hypothesis regarding its patterns, but the leading one was that there was a massive planet tugging on Uranus.
As shown in this poorly drawn diagram, as Uranus approaches planet X, it goes faster, and as it goes away from it, it goes slower. And as fate, and calculations using Newtonian mechanics would have it, what do you know, it is another planet, later named Neptune! However, its discovery caused an international turmoil I won’t go over, since two people discovered it around the same time, one was English, and the other was French. And as stupid politics would have it, both countries wanted the discovery to be of their own. And so, using physics, a planet was discovered in the coolest way possible, by predicting that it existed before they knew it existed.
There was another problem, though. Neptune also seems to have an anomaly… except it was based on crummy observations, that is all. Even if there were anomalies, Pluto is too small to do it. Oh, and a correction of the mass of Neptune by Voyager 2 in 1989 erased all doubts, there were no anomalies. But, this is the early 1900s, so I am getting ahead of myself. Percival Lowell, searching for a non-existent planet X with crummy observations, but the right calculations, funded a series of three searches for planet X. After the failure of the first two, Clyde Tombaugh found Pluto by two major coincidences. It is so coincidental that I still go into cardiac arrest everytime I hear about it.
The first coincidence can be summed up by the statement: “Inclined to be eccentric.*” Ok, this bad pun is not of my own creation, it is from someone in my astro club, so blame him, Ok? Now, Pluto has a bizarre orbit that is quiet elliptical, and it is tilted to around 17 degrees. How tilted, you ask? I will let this diagram speak for me:
(note how in its lowest and closest point, it is closer to the sun than Neptune for 20 years (ex: 1979-1999))
So, the first luck is this, Pluto was in the plane of ecliptic like all the other planets in the year 1930. The astro club showed it in the nifty program called Starry Nights, in which they winded time back, and indeed, it was veeerryyyy close to the ecliptic. This coincidence wouldn’t have been so astonishing without the second luck. The second luck is this, you know that correct calculations done on the crummy data? Well, the result was coincidentally very close to the place where Pluto was in 1930. Therefore, two things had to happen, Pluto had to be on the ecliptic, and the calculation based on the incorrect data had to point in the right place! I find this coincidence so striking that I think the statement, “What, you think it was all a coincidence?” no longer holds sway on me. That year, after comparing two photographic plates, Pluto was announced and it earned planetary status.
Years afterwards, more information were found about it. Firstly, it is a double system with its moon Charon. They orbit a center of gravity outside Pluto. Not only that, Charon is disproportionately large compared to its mother planet, around a ration of 1/2. Only the Earth-Moon system is comparable, in which Earth’s moon is 1/4 its size. Not only that, it is disproportionately close. Let’s put this on scale, shall we? Imagine an average sized globe, one of those you buy in stores, and have a ball 1/4 its diameter. Then their distances would be 30ft. Now, compare that to Pluto, around 1/2 the size of the moon to Charon, 2/3 the size of Pluto. Then their distances would be around 7 inches! So close together were they that Pluto seemed like it had a huge mountain initially. Very recently, two other moons were found. They are much smaller than Charon, and they are called Nix and Hydra.
They also know its chemical composition on its surface by spectroscope. It is 98% nitrogen, with other frozen gases. Its density suggests it is a mixture of a sludge of ice and rock, with 70-50% rocks, and 30-50% ice. It is also thought to be similar to Neptune’s moon Triton, which has a retrogade orbit similar to Pluto around Neptune. The degree in which Pluto rotates is weird. It is even more lopsided than Uranus, with an axis tilted to 122 degrees. One final interesting fact is that Pluto will never crash with Neptune because they are in a 3:2 resonance. Meaning, every 3 orbits from Neptune, Pluto orbits twice.
As of recent history, Pluto has been demoted from its planethood status in August 2006, thanks to the growing number of Kuiper belt objects. Pluto is still an object of interest, though, and a space probe named New Horizon is going to Pluto as of right now, and it has just passed Saturn’s orbit a few months ago. With the helps of instruments like Lorri, Ralph, and Rex, they will figure out a whole lot of things about Pluto, things that could not be done with Earth based telescopes because Pluto is freaking small and far away. (Scientists should stick to science, instead of cheesy acronyms) It will have only a six months window to investigate because the spacecraft is going really fast, and Pluto, being small, has a pathetic amount of gravity. When it gets there, there will finally be a good picture of Pluto! I hope I don’t die or become blind before then. Once it passes Pluto, it will investigate other Kuiper belt objects.
Wow, that was a mouthful! Now that you know a lot about Pluto, you will be rewarder with pixelated pictures of Pluto, and a poem of Pluto! What, you are not happy with it? Then suck it up.
(Translation: Pluto and Charon are freaking small)
Oh, and to finish things off, an ode to Pluto, by Greg Lee of my astro club:
ODE TO A LOST PLANET(with apologies to
Blake and Shakespeare) — Greg Lee
Pluto, Pluto, flung so far,
How we wonder what you are.
Like a comet from the void,
Like a distant asteroid.
Unlike others we have seen,
Interloper in between.
Though you have a proper name,
Do you need some other fame?
Many monikers employed:
“Minor Planet”, “Cometoid”,
“Mesoplanet” some propose,
“Nearest of the TNOs”.
Like the rose by other name,
Are you scented still the same?
With so many names to call,
Are you one?… or are you all?
*(Eccentrity in math describes how elliptical, or ovalish an object is. The higher the eccentrity, the more ovalish it is, as in Pluto’s orbit. Oh, and the inclined in the pun describes the way Pluto is inclined at 17 degrees.)