The problem with Pluto

by Tanya
Publish date
18 February 2013
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On 18 February 1930, Clyde Tombaugh achieved an amazing feat - he discovered Pluto. It’s said that he was a meticulous astronomer and I’m sure he must have needed all that mettle to have stumbled upon the tiny speck that was Pluto.

Over six years ago, Pluto grabbed headlines when astronomers famously ‘demoted’ the planet and designated it as the first of the dwarf planets. Some were disappointed by this – but I have to say that Pluto has always been a bit of an odd-ball. It was something we had explored a year earlier with the release of our planetarium show, The Problem with Pluto, in 2005.

The Problem With Pluto In this planetarium show, Lucy is on a research craft with her mother Lillian, a scientist, and together they are gathering data to discover just what Pluto’s status should be.
Image: Melbourne Planetarium
Source: Museum Victoria

A fellow astronomer shared with me his interesting way to explain it. Imagine, as a child, having a case full of pencils. The pencils came in all different colours but at their heart they were the same; except for one. It was a bit odd, still good for colouring-in just like a pencil, but there was something different about it. Nonetheless, it was the only one you’d even seen and it had always been in the pencil case, so you called it a pencil along with all the others. Then, one day at a friend’s house, you opened their pencil case and it was filled with something called crayons. Your eyes lit up with recognition. That odd-ball pencil you’d been worried about wasn’t odd after all, it was in fact a crayon.

When Pluto was discovered, it was one of a kind at the edge of the Solar System. It wasn’t a terrestrial planet, it wasn’t a gas giant, but it did orbit the Sun. Seventy years on, we now know of thousands of objects orbiting alongside Pluto. They are the icy worlds that make up the Kuiper Belt. Pluto, because it is big enough to be round, is still a bit special and so it now goes by the new label of dwarf planet.

On Pluto Day, I’ll be celebrating that Pluto has now found its rightful place in the Solar System.

New Horizons spacecraft Right now, a real research craft is on its way to Pluto. Called New Horizons it will fly by Pluto in July 2015 and journey on to discover more about the Kuiper Belt.
Source: NASA


The Problem with Pluto will be showing at the Melbourne Planetarium at 2pm, 18 February to 4 March.

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