IT'S HAZARDOUS being a planetary astronomer, at least it is if an e-mail sent to the man who triggered the fall of Pluto is to be believed. For David Jewitt, 48, professor of astronomy at Hawaii University and famous with his student Jane Luu for discovering the first Kuiper Belt objects that led to the former planet's demotion, tells how he received a death threat for his efforts. 'I get a lot of unsolicited e-mails from angry people,' he said. 'This one guy wrote what started like a completely normal e-mail but he worked himself into a frenzy by the end of the second paragraph and said he wanted to kill me. 'He started by saying, 'I've read your web page about the Kuiper Belt and Pluto', but then got angry. 'How dare you upset my son,' he said, 'how dare you change this stuff,' then started to use four-letter words and said he was going to come to Hawaii to get me.' Luckily for Professor Jewitt, who was at the University of Hong Kong this week to deliver a lecture on 'The New Solar System', the writer didn't make good on his threat. The episode underlines the emotional attachment to the former planet that led to a bizarre attempt by the International Astronomical Union (IAU) in Prague this year to redefine a planet by virtue of its roundness and orbit. Professor Jewitt is scathing of the mental acrobatics that nearly expanded the planets to 12, including Pluto: 'The IAU really screwed it up. It botched the whole thing. First of all why were we voting on this issue? It's supposed to be a science organisation right? We don't vote on other stuff, gravitational matters or the Earth's mass. It was absurd. The IAU formed this committee that worked for two years in secrecy and was then dissolved because it couldn't find an acceptable answer and replaced by another committee which also worked in secrecy for a long time and came up with this crazy system that was laughed at.' The committee stipulated that a planet had to be round, but there was also a condition about where the centre of mass of orbiting binary bodies lay if it was a binary, which, Professor Jewitt said, became embroiled in confusion about what happened with eliptical orbits, 'because then the centre of mass would go in and out'. A body could be a planet for half its orbit and not the other. 'The committee made a mistake by even agreeing to do the job. It was going to fail from the start because according to committee chairman Owen Gingrich, the objective was not to be too offensive to the public interest - whatever that is - because they'd been beaten up a few years before by the public and newspaper reporters saying they were mean-spirited, evil, narrow-minded SOBs for trying to demote Pluto. 'They didn't want to do that and were very clear about it. They tried to work out a way they could give Pluto another label so that people who were not reading very carefully could still believe it was a planet while officiandos who read every word would understand it was a different kind of body.' Professor Jewitt says the nostalgia over Pluto's planetary status is irrelevant. To him it is simply the largest object in an icy region of the solar system beyond Neptune called the Kuiper Belt. He explained in his lecture that it made much more sense to group things in space by the way they were formed and their properties. Using this method, the solar system falls into three regions. 'There are the rocky planets in the inner parts of the solar system; Mercury, Venus, Earth, Mars. They're all made of rock and grew in roughly the same way as far as we know, and you can include the asteroid belt with them. Then you have the giant planets, of which there are two kinds - gas and ice giants, formed in a distinct way again. You also have all this debris, which is the Kuiper Belt and the stuff in the Oort cloud [a postulated spherical cloud of comets about 50,000 to 100,000 astronomical units - one unit is 93 million miles - from the Sun], and that's separate again. So I like to think of these three domains; the terrestrial planets, giant planets, and the domain of the comets. Pluto is one of those.' It was in 1992 that Professor Jewitt and his graduate student Jane Luu discovered the first objects in the Kuiper Belt. Although one astronomer had argued it was unlikely that Pluto was alone in the region when it was discovered in 1930, a persistent publicity campaign by its parent Lowell Observatory, pushed for its status as a planet. Professor Jewitt thought it odd that the remote space beyond Neptune should be so apparently empty and set about investigating it using emerging digital technology and advanced telescopes in Hawaii. 'It started out sounding like a crackpot enterprise because the proposal to the allocation committee to get telescope time said we thought the outer solar system had some unseen things in it, but basically that's all we could say. The reviewers said well, yes, but who cares? We got around that by lying, saying we were going to do measurements of a different kind and then carried on looking.' The lies paid off. By the end of 1992 the world knew that Pluto was not alone, and there are now hundreds of thousands of objects charted in the region, discoveries that led to the former planet's reclassification. 'It's just another one of them,' Professor Jewitt said. 'Only bigger', a large, frozen comet that would melt and fizzle out were it not king of its icy domain. Professor Jewitt has come a long way since his interest in astronomy was sparked by a meteor shower as he rode his bike home in Tottenham in 1965 when he was seven. The son of working class parents, he was just one of three students out of 140 to go on to university from his comprehensive school, inspired by the Apollo space mission and achieved by focusing on physics 'at the expense of many other things'. He studied planetary geology at University College, University of London, going on to Caltech, California and then to MIT, before moving to Hawaii because of the quality of the observatory and telescopes there. And he is excited about a new opportunity to further his studies of the Kuiper Belt. 'There is a new telescope about to come online in Hawaii called Panstars that is going to be revolutionary in its power,' he said. ' It has huge discovery potential because it does the whole sky with two billion pixel CCDs. It goes deep, repeatedly, doing the whole visible sky every four to five days.' The telescope, which comes online in April, is funded by the US Airforce. 'We told them we needed it to help stop incoming asteroids. That was the pitch,' he said.
