Pluto, the Unpredictable

In 1916, English composer Gustav Holst bestowed upon us his wonderful orchestral suite known as The Planets. Each piece of music, or 'movement', was named after one of the eight planets, from Mercury 'the Winged Messenger' out to Neptune 'the Mystic', and it soon became a celebrated and much-performed suite. However, a good few years later he faced a slight problem when American astronomer, Clyde Tombaugh, discovered what had become known as 'Planet X', a term coined by fellow astronomer, Percival Lowell, who was convinced of the existence of another planetary body beyond the distant orbit of Neptune but had failed to find it.

This was of course Pluto and, while this was a major discovery at the time and made headlines around the world, it did kind of mess up Holst's work. He actually only lived for a few years after Pluto's discovery but surprisingly showed no interest in writing a movement to represent the new member of our Solar System's family and bringing his old suite up to date. Many years later, however, a conductor named Leonard Bernstein worked an improvised performance into a recital of The Planets which he named Pluto, the Unpredictable, and it proved to be a fitting name.



Indeed, from its discovery in 1930 right up to this year, almost nothing was known about Pluto. We had determined its approximate size and guessed at its composition, and even found that it was orbited by a comparatively giant moon known as Charon, but that was about it. It had not been observed up close even all these years after its discovery, with the best images coming via the mighty Hubble Space Telescope whose observations had enabled us to piece together a computer-generated image showing only the vaguest of surface features (as shown above). To all intents and purposes though, poor little Pluto remained the only one of the 'classic' nine planets to have never been visited by a man-made probe. That is, until this year.

NASA's New Horizons probe was launched in January 2006 and, unlike earlier missions to the outer reaches of the Solar System, it was designed to visit one planet only - Pluto. Well, I suppose it's not a planet any more, technically, but during my youth it was, and it was always a planet that captured my imagination as well. What was this tiny rocky body doing out beyond the four gas/ice giants, so far from the other terrestrial planets? And why did it have such an eccentric, inclined orbit? Hopefully any day now we should receive some of the answers to these questions that we've been asking for up to 85 years as New Horizons has just zoomed past the icy world, clacking its camera and whirring its scientific gadgetry as it went, and we should also, finally, get to see what the (dwarf) planet looks like as well.

It's an exciting few weeks to be an astronomy geek that's for sure! So far we've received the fascinating image below which constitutes the first ever detailed look at Pluto. That in itself is cause for celebration if you ask me, but we still have a lot more to come as New Horizon's treasure trove of images and data wings its way across space, reaching for our antennae. If you have anywhere near the level of interest in this as I do, keep your eyes on the news over the next few days - it'll most likely be the last time any of us witness such a historic event...

Top Five Planets

For the longest time there were only the nine planets that were known to us, with this number of course being controversially reduced in eight in more recent years, and they have become incredibly familiar to those of us who care to glance skywards now and then, but now countless more have been discovered orbiting alien stars. Many of these appear to be even stranger than we could've imagined but for most of us, none of them will ever hold the allure of the more familiar worlds that are closer to us. Perhaps one of them was the first sight we gazed upon when first looking through a telescope; perhaps one was the subject of a favourite childhood science-fiction tale; perhaps it's simply a particular alien quality of one of them that we find appealing, but I'm sure we all have our favourites. And these are mine:

5 - Venus

Long considered Earth's twin, this comparably-sized planet features hellish conditions that no life from our home could endure. Its atmosphere has constant lightning and is so dense the first few Venera probes sent by the Russians were crushed before reaching the ground. Even the ones that did manage to land unscathed only lasted an hour or so before melting. There is also sulphuric acid rain, every part of the surface features evidence of volcanic activity, and the entire planet leaves a tail behind it in space, much like a comet, due to the Sun's solar wind!