By now you've probably read a bunch of stories in the media about how Pluto is still a planet, how astronomers have decided it's the head of a new class of planets called "plutons" and how millions of school children will be relieved to know that everything they were taught in school about planets isn't wrong. Of course, that's not the only news coming out of the International Astronomical Union meeting in Prague this week, but it seems to be the story the mainstream media has latched onto with great gusto.
On Tuesday, CNN's lead science story focused on how Pluto could shortly lose its planet status. I thought they were sort of jumping the gun, since I'm pretty sure they had the same advance embargoed press release that I did, explaining the IAU's proposed new classifications for planets. (Embargo means that the news is released early so that the media can prepare stories, but they can't print or release the story until a specific time. In this case, the news was sent out early Tuesday for release at 2 AM Eastern Daylight Time in the United States). So, they had all day yesterday to put together some story that would prepare people for the proposal by the IAU to keep Pluto as a planet AND make some new classifications of planets (including the Sun) that would help us understand the nature of the largest bodies that orbit stars.
To be fair, CNN's story today (go to CNN.com) leads the news on the website, with a real emphasis on how our perceptions of the solar system have changed with discoveries of new solar system bodies.
Still, it's tough to blame the media for latching onto a story that's easy to tell in screaming headlines: Pluto Might Not be a Planet: Children Everywhere Dismayed! It's got drama, science, crying children, duelling scientists: what's not to like?
Maybe I'm tough on the media; I was trained as a science journalist and have worked in astronomy research, so I can see both sides of the story. Rarely does the whole story get into the papers. For one thing it's just too tough for the average reporter to take a complex science topic and write about it well. There ARE good science writers out there, but they're not as common at media outlets as we'd like to think. And they have to report on all science, not just astronomy. But, since astronomy is a science that can take you pretty easily into all sciences, and because it excites people's imaginations so well, I'd sure like to see better reporting on it.
But, I digress. There are several REAL stories here about Pluto and the planets. One of them is that astronomy has always been at least one part observation, one part theory, and one part classification of what we've observed. Rethinking our definition of "planet" is actually a long-overdue move on the part of astronomers. Back when our telescopes could barely show us even such giants as Jupiter and Uranus, it was pretty easy to classify planets into the scheme we used for hundreds of years. Now that we have telescopes (both on Earth and in orbit) that can show us mere specks of ice and rock in orbit in the most distant reaches of the solar system, as well as giant planets (and some not-so-giants) around faraway stars, the business of classifying what we see got more complex. Pluto has always been called a planet, but in recent years we've found objects that are bigger than Pluto, albeit farther away. What to call them? And if they're planets, what's that make Pluto? The situation needed clarification.
So, the IAU (which was charged by the world's astronomers to come up with a solution) proposed that we refine our classifications of what planets are. Their decision, which still has to be voted on by the astronomers meeting in Prague, clarifies the parameters for what's a planet and what isn't by applying some easy-to-understand definitions.
What they've done is to keep Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune as "classical planets." But these aren't the only planets. There's a new class of them out there, of which Pluto is the king: the "plutons." This is what astronomers will now call the rapidly growing class of worlds being discovered in the outer reaches of the solar system. This includes Pluto and Pluto-like objects. You may have read about the discovery of some of these plutons in the past few years, like the one called Quaoar. Ceres, formerly called a minor planet, is also part of this group. These plutons likely outnumber the classical planets by many orders of magnitude because there are so many of them out there. We haven't discovered them all, but they are part of the solar system's most distant population of objects, which astronomers are exploring with stronger and better telescopes each day.
So, the story here is that Pluto's still a planet, for sure. But, in coming up with the new classification, astronomers are doing what they've always done when their technology improves and shows them more variety in the universe: they find new ways to describe the new objects. We did it with galaxy types, we did it with star types, we're doing it with cluster types, and now we're doing it with planet types. And that's the way science often works. New types give new understanding and help resolve old disputes. While not all astronomers are going to completely agree with the IAU's proposal, I think most of them recognize that somebody had to bring some order out of the chaos introduced by the discovery of so many new objects out on the frontiers of the solar system.
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