Wednesday, January 06, 2010

What Happened to Pluto?

We visited the Museum of Science in Boston over the Christmas break, mostly to see the Harry Potter Exhibit (more on another post!), but we also had the opportunity to see the very last showing of "What Happened to Pluto" at the Hayden Planetarium. The planetarium will be closed for renovations for a whole year.

When they interviewed people on whether they felt Pluto should remain a planet, invariably the older generations said Yes! and the younger generations said no.  I can't let go of the planet mnemonic "M VEM J SUN P" so I guess that puts me with the old fogies.  Dova resoundingly said that Pluto was NOT a planet when I asked her.  During the show, I even learned a new mnemonic, "My very excellent mother just sent us nine pizzas".  According to Urban Dictionary, since Pluto is no longer considered a planet, you'll have to use "My very erotic master just showed up naked."  Oops!  This is a family blog!

I remember the hubbub about downgrading Pluto's status as a planet back in 2006, but I didn't understand the details until I read this children's book, The Planet Hunter: The Story Behind What Happened to Pluto.  (Sometimes science is best explained by children's books, even for this engineer.)

So what happened to Pluto's status?  The Planet Hunter describes astronomer Mike Brown's quest to find planets ever since he was a boy.  After many years of searching, he finally found planet-like objects in the icy Kuiper belt. In 2007, he and colleagues determined that one object, Eris (formerly UB313), was actually heavier than Pluto. The International Astronomical Union (i.e. egghead group of astronomers) finally put more requirements into the definition of a planet, which left poor Pluto out.  Pluto and other orbiting objects like Eris are now considered dwarf or minor planets.  There's even a planet named Santa because it is round and fat. It's much easier to understand with cool names and illustrations!

But it will be a while before all the textbooks and displays of the solar system are updated. It will be so flat and boring without that tilted elliptical orbit!


MIT Mommy said...

Of course, having taken the solar system class at MIT, I have a personal affinity to planets and was sad to see Pluto left out in the cold. =(

I hear some new planets have been discovered, but it just won't be the same.

Happy New Year, by the way. I saw pictures of 26-100 tonight at our board meeting and thought of our outing!

Alan Boyle said...

I hope you'll also give a look to my book, "The Case for Pluto," which has an appendix that focuses on what to tell your kids about planets. Pluto should be seen as a different kind of planet, although it sounds as if it might be hard to tell Dova that. :)

Laurel Kornfeld said...

Textbooks and exhibits do NOT have to be updated because this issue is still very much a matter of debate. Many young people also favor the view of keeping Pluto as a planet. Only four percent of the IAU voted on the controversial demotion, and most are not planetary scientists. Their decision was immediately opposed in a formal petition by hundreds of professional astronomers led by Dr. Alan Stern, Principal Investigator of NASA ’s New Horizons mission to Pluto. One reason the IAU definition makes no sense is it says dwarf planets are not planets at all! That is like saying a grizzly bear is not a bear, and it is inconsistent with the use of the term “dwarf” in astronomy, where dwarf stars are still stars, and dwarf galaxies are still galaxies. Also, the IAU definition classifies objects solely by where they are while ignoring what they are. If Earth were in Pluto’s orbit, according to the IAU definition, it would not be a planet either. A definition that takes the same object and makes it a planet in one location and not a planet in another is essentially useless. Pluto is a planet because it is spherical, meaning it is large enough to be pulled into a round shape by its own gravity--a state known as hydrostatic equilibrium and characteristic of planets, not of shapeless asteroids held together by chemical bonds. These reasons are why many astronomers, lay people, and educators are either ignoring the demotion entirely or working to get it overturned.

Mike Brown represents only one side of this debate. I urge you to buy "The Case for Pluto" by Alan Boyle. It is easy to read and has a section at the end about how to talk to kids about planets in general and Pluto in particular.

Asianmommy said...

Haha! I've never heard of these mnemonics. So funny. Too bad the updated one is not suitable for little ears.

Momisodes said...

I am still giggling over those mnemonics!

I had no idea they are closing the planetarium for a year. I took Dadisodes on a date there last year :)

We're total geeks.

Kady said...

A pluto-less variation on the mother mnemonic:

My Very Educated Mother Just Servied Us Nothing!