The AstroArt of David A. Hardy
In this section you will find articles written by David on various subjects that interest him – and hopefully you!
1. Is Pluto a Planet?
Oh, yes, it is. Oh, no, it isn't!
Discovered in 1930, Pluto was, until quite recently, regarded as the ninth planet.
"Men very easily make jugs serve useful, necessary. . ." erm . . . we seem to have lost our "purposes"?
Well, that's how I learned to put the planets of our Solar System into their correct order when I was a boy, but that all seems to have gone to pot during August, 2006. The IAU (International Astronomical Union) consisting of 2,500 astronomers from around the world, has been meeting in Prague and have been discussing the weighty matter: Is Pluto a planet, or not? And if it is, what about the other 'new' planets that have been discovered recently?
A New Order
On August 16th, the IAU announced that the 'new' Solar System will consist of: Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Neptune, Pluto, Charon, and the snappily-named 2003 UB313 (presumably a sort of UB40 for unemployed planets?). However, this one had already been unofficially named Xena, apparently after the star of some TV programme or other; in October 2006 it was officially re-named Eris, appropriately after the Greek god of discord. Its moon is now named Dysnomia, after the daughter of Eris, meaning 'lawlessness'. And the actress who played Xena was Lucy Lawless? Hmmm. . . Publishers hastily made plans to update their astronomy books and encyclopedias, while school teachers ripped down the mobiles hanging from their classroom ceilings in order to add the new objects. NASA wasn't too happy, because its probe New Horizons is due to rendezvous with the 'ninth planet' in 2015.
"The solar system is a middle-aged star, and like all middle-aged things, its waistline is expanding," said Jack Horkheimer, director of the Miami Space Transit Planetarium and host of Public Broadcasting's Stargazer television show. Opponents of Pluto, which was named a planet in 1930 by its discoverer, Clyde Tombaugh, still spoiled for a fight. Earth's Moon is larger; so is Xena, about 70 miles wider. In fact, there are many moons of Jupiter and Saturn that are bigger than some of the objects that now qualify as planets, such as Mercury ~a fact that bothered some astronomers. But the IAU said Pluto meets its proposed new definition of a planet: 'any round object larger than 500 miles in diameter that orbits the Sun and has a mass roughly one/12,000th that of Earth.' Moons and asteroids will make the grade as long as they meet those basic tests. 'The new objects will be known as 'plutons'', said the IAU. "Hold on just one cotton-pickin'minute there!" hollered the geologists. "We're already using that term to mean magma that works its way into rocks". Red faces amongst the IAU!
So the news item around the world was that there are now not nine but twelve planets. My own gripe with this was that there should have been twelve even without including Ceres (previously an asteroid) and Charon (a moon of Charon, for Pete's sake!). What about those other new planets, Sedna (reverse anagram of Andes?) and Quaoar? Well, actually they are all just Kuiper Belt Objects (including Pluto), and there are probably thousands or millions of those, so what's all the fuss about? Well, it all came to nothing anyway. The BBC website was one of the first to announce'"Forget all that. Pluto isn't a planet after all'.
Look at the Beeb site
As an aside, take a look at that BBC website, which is here.
Click on the small illustration to zoom in on it. Does Charon look a bit familiar? It should do, because everyone reading this has seen it in our own sky for as long as they've been alive: it's our Moon. Good old Auntie Beeb and its cheapo artists! But anyway, the announcement was that 'Astronomers have voted to strip Pluto of its status as a planet. It will now be known as a 'dwarf planet''. One reason for this change of heart is that with so many new bodies being discovered on the edge of the 'old' Solar System, we could end up with 50 or more planets. (Well, why not? The more the merrier, some might say!) Amid dramatic scenes in the Czech capital (says the BBC site, although actually only a handful of astronomers were left in Prague by now) which saw delegates waving yellow ballot papers in the air, the IAU voted to block this possibility - and in the process took the historic decision to relegate Pluto. The scientists agreed that for a celestial body to qualify as a planet:
it must be in orbit around the Sun
it must be large enough that it takes on a nearly round shape
it has cleared its orbit of other objects
This last criterion has already met with opposition, because nearly all of the planets, including Earth, are in fact still surrounded by debris left over from the formation of the Solar System ~ hence meteors.
But frankly, I think the scientists and astronomers have rather blown it by ignoring public sentiment, and the historical significance of Pluto. And after all, ultimately it is the public (usually the US one) who pay the bills for space exploration; and who's going to want to send a probe to some nonentity? Well . . .
As I write, NASA's New Horizons spacecraft is due to make its fly-by of the dwarf planet on 14th July 2015. It has already sent back images of Pluto and Charon as it gets closer, and there is considerable excitement in scientific and astronomical communities. There are discussions on subsurface oceans and 'cryovolcanism'. See this video (in which my work appears, briefly) here.