There used to be nine planets, as every school kid knew. Back then, you could keep your red Mars and your ringed Saturn. I felt a special kinship with Pluto because it had been discovered on my birthday (February 18). Now, what's happened to Pluto shouldn't happen to a Dog Star.
In 2006 the International Astronomical Union (the IAU) got together and demoted it from full planetary to "dwarf" status. Sure, Pluto is small—just 1/6 the mass of our moon and 1/3 its volume —but we've always known that, so why change the rules after 75 years?
The IAU reviewed the qualifications for planetary status, and found that Pluto failed to qualify. The three necessary criteria are: (1) It must orbit the sun, (2) have sufficient mass to assume a round shape, and (3) "clear its neighborhood" of space rocks in its path. So what's the problem?
Icy little Pluto is fairly round and it orbits the sun, but the IAU decided that it does not meet the third criteria of "clearing the neighborhood" because its exceptionally elliptical orbit crosses that of Neptune's. Oddly enough, under this rationale other planets in our solar system, including the Earth, would also fail to meet the "clearing the neighborhood" test. We encounter asteroids and other space objects in our own orbit all the time.
It may be stretching a point but it occurred to me, while thinking about all of this, that men are from Mars and women from Pluto—not Venus, as we have heard. Why? Because Pluto was downgraded to a status far below its larger, more formidable neighbors. That's second-class citizenship by any other name, and a lot of women here on good old Mother Earth can relate to that.
But back to the plight of Pluto. A lot has been written about whether our tiny, distant neighbor is, or is not, a planet. In the end it seems to come down to its cozy relationship with Neptune. Those responsible for demoting it to a "dwarf" point to its irregular orbit, which often brings it closer to the sun than Neptune's, and making it appear more like an eccentric moon.
Still, others argue that earthly politics played too great a role in what the IAU did in 2006, and want to see Pluto given another chance. That chance may come this July, when a NASA piano-sized spacecraft named New Horizons, launched nine years ago, is scheduled to do the first ever flyby of Pluto. It will be gathering never before known facts and measurements, plus pictures, that will give us earthlings our first glimpse of that far-off chunk of ice. So, is Pluto "ready for its close-up?" And afterward, will it change anything? Will those who advocate the return of Pluto to a fully-accredited member of our solar system prevail? Stay tuned.
With less than 100 million miles to go before reaching its destination in July, New Horizons has already begun sending back data. People, we are watching history in the making!