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I can finally admit it. Pluto is not a planet.
- May 21, 2009 at 1:02 PM
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- Comments (9) Total Views (1423) Everyone can see this journal post.
I do not like change. It has been some time since Pluto was demoted from planetary status (2006). This has been pretty hard for me to accept, and despite my best effort at ignoring the demotion, it did not go away. Our solar system has 8 planets currently recognized by the International Astronomical Union (IAU) - Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
My reasons for holding on to Pluto have been based purely on my despite of change. In general, I accept changes to other scientific classifications, based on new data, or out of necessity for clarification. For some reason, Pluto was different. Until now. But images like this from orbitingfrog.com still make me sad for the change.
Picture © 2008 Jerome A. Popiel
I recently read and reviewed The Handy Astronomy Answer Book by Charles Liu. It is really an incredible book. The author does such a great job of explaining nearly every astronomical topic in such clarity, in a logical order. The answers tell a complex story in terms most people (including myself) will understand and appreciate.
There it was, page 128. As I began reading the definition of a planet, I was expecting to still see "outdated information" accepting Pluto as a planet. After all, any book written prior to 2006 will not reflect its change in planetary status. Well, this book was printed in 2008. So any respectable astronomer will not tolerate having outdated Pluto information in his book, despite what history, or his emotion or own preference tell him. And so, I was faced with facts; facts I cannot ignore.
Quoting from the book, p 128:
Generally speaking, a planet usually refers to an object that is not a star (that is, has no nuclear fusion goign on in its core); that moves in orbit around a star; and is mostly round because its own gravitational pull has shaped it into, more or less a sphere.
The author goes on, to define the general characteristics of the planets in our solar system. According to the new classification system, a planet must satisfy three criteria. First, a planet must be in hydrostatic equilibrium (balance between the inward pull of gravity and the outward pul of its weight and structure); an object in this state is usually spherical. Second, a planet's primary orbit must be around the sun; moons do not count as planets because they orbit planets, not the sun. Third, a planet must have cleared out other, smaller objects in its orbit and be the largest body in its neighborhood orbit. This last criterion was added in 2006 as the IAU clarified the definition of a planet.
Criterion number three is where Pluto fails to meet the new guidelines. It turns out there are thousands of objects in Pluto's neighborhood that is has not cleared, and it crosses the orbit of Neptune, making it NOT the largest object in its orbital path. OUCH. With a definition and facts like that, it's hard to make the case for Pluto. Alas, at the same time Pluto lost its planet-hood, a new designation of dwarf planet was given. A dwarf planet is that which satisfies the first two criteria (see above), but not the last one. In addition to Pluto, the other dwarf planets in our solar system are Charon, Ceres, Eris and Quaoar.
Prior to 2006, planets were historically recognized based on the fact they orbited the sun and were of a certain size (considered large, meaning greater than 2,000 miles in diameter). Smaller objects were designated as asteriods. While the original system had flaws, and the new one may also, having a system that has been agreed upon by the scientific community gives us a starting point for educating everyone about facts of the solar system.
Picture from the JPL
It turns out, I like this new system now that I have read about it and understood it. Now, instead of memorizing nine names and their order from the sun, we memorize 14 names, their position from the sun, and understand the reason for the different designations of planet and dwarf planet. This last point is the key; we will learn to understand, not for the sake of memorizing facts. Although that was not the point of reclassification, its a pretty nice side effect. Another side effect? Pluto may have lost a label but certainly gained in popularity with all the discussions about its fate!
Tonya
AKA sunmoonstars
Comments:
I heard this from a friend a while back. I also didn't want to believe it. I have a strange connection with that...whatever you call it.
How do you pronounce Quaoar? I must have missed that class of Planetary Astronomy!
OK. I just looked it up and it was discovered in 2002. Not my fault that I don't know about it, then! And, it's pronounced pronounced /ˈkwɑːwɑr/ KWAH-wahr. Yay, Wikipedia!
There's a really good article on the Wiki about planetary nomenclature, by the way, which the Quaoar page led me to.
I admit that I am very very sad that Pluto is no longer a 'planet'! Geez a loo! Gosh and I had to find out from a group of fourth graders I walked past...Didn't I feel old!
evws - I had a feeling someone would ask that! And wow that wiki article has alot of info :)
http://en.wikipedia.org/wiki/50000_Quaoar
I've never been upset that Pluto lost it's planetary 'status'. Perhaps we humans have a special place in our hearts for planets since we happen to live on one?
My excitement over the discovery of the other bodies in our solar system has far outweighed having to accept Pluto as a dwarf planet. Now, where I had no information and pictured nothingness, there are more exotic places to learn about.
I'll be smiling when every school-child knows the names and order of each planet and dwarf planet. Imagine how the solar system seems to get more dynamic with the addition of many dwarf planets, moons, asteroids, comets and Kuiper belt objects! Sedna is difficult to classify and can add a spark of interest to kids who maybe bored of the old MVEMJSUN memorization model.
In fact, teachers could use the entire classification controversy to teach the methods of grouping, how it must change as new information is presented, and how the general population is often taken out of its comfort zone when, even Pluto-sized, alterations are made.
I don't miss Pluto! It's still there. Or I should say, it's still here: with the sun, with us, with the variety of other bodies that make our solar system spectacular.
Paxmommy, I LOVE you point of view! That's a great point, about how much more alive the solar system is with all the other bodies. I think back to my childhood with 9 planets, and it does seem pretty bland compared to the really of it now. You rock~
Thanks Tonya! You know I'm a space nerd:)
Thanks for science blogging. I look forward to each and every piece you write.
LOL! This made me giggle :D
I did a report on Pluto and its moon in elementary school. I worked SO hard on spray-painting those little foam balls and writing my two-page essay on why Pluto is the best planet.
One of my favorite quotes about this whole thing is "Aww, don't worry Pluto. I'm not a planet either." Haha!
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Nope. Sorry. Pluto is still a planet in my world. even if it is a dwarf. lol.
- MythicMMM
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