What Did Pluto Ever Do to Astronomers?
Generations of us grew up with popular little planetary mnemonics that varied from place to place but all had one very simple function: to help us remember the nine planets, in their order from closest to the sun to farthest from the sun.
Yes, I said nine.
The version I was taught was, “My very educated mother just showed us nine planets.”
There were other versions, including “Men Very Easily Make Jugs Serve Useful Needs, Perhaps,” “Mary’s violet eyes make Johnny stay up nights plenty” and “My Very Easy Method Just Speeds Up Naming Planets,” among others.
The first letter of each word in these little mnemonics stood for a different planet: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.
Poor little Pluto was first discovered in 1930 and was considered the ninth planet (and as far as we know so far, the ninth and final planet) in our solar system. Those little planetary memory aids have been around since the 1950s.
As early as 1992, the year I graduated from college and was, thereby, through with having a great need to keep up with the order of the planets in our solar system, Pluto’s planetary classification came under fire.
Then it happened.
In 2005, an organization called the International Astronomical Union, a name that sounds like something out of some random science fiction movie, decided to “formally” define the term planet after astronomers discovered a different object out past Neptune believed to be even larger than Pluto but still smaller than everything else. The IAU came up with a definition that knocked Pluto right out of the planetary race.
Suddenly, as of 2005, we no longer had nine planets. We had eight planets and a “dwarf planet” or “planetoid.” That seemed to knock the wind right out of “My Very Educated Mother Just Showed Us Nine Planets’” sails.
Of course, since I was done with school and not once called upon since to name the planets in order off the top of my head, I didn’t keep up with any mnemonics that might have been employed to take the place of the one I used. But I assume something must have replaced at least a few versions, since “My Very Educated Mother Just Showed Us Nine,” doesn’t make a great deal of sense.
But now the controversy over tiny, cold Pluto has fired up again!
This new controversy involves something known as a “solar wind” and its effects on Pluto as observed during New Horizons’ flyby through the Plutonian system in July 2015. The spacecraft’s equipment measured something unusual — click here for a much more detailed explanation — that was something they’d have expected from a bona fide planet, not some second-rate “planetoid.”
So while Pluto still isn’t getting the “planet” status, there are new questions about whether it might just deserve to be back on the list.
In today’s over-litigious society of ours, I’m surprised the little guy hasn’t already filed a lawsuit.