<Table> The Pluto Files <Tr> <Td_colspan="2"> </Td> </Tr> <Tr> <Th> Author </Th> <Td> Neil deGrasse Tyson </Td> </Tr> <Tr> <Th> Language </Th> <Td> English </Td> </Tr> <Tr> <Th> Subject </Th> <Td> Astronomy, Pluto </Td> </Tr> <Tr> <Th> Publisher </Th> <Td> W.W. Norton & Company </Td> </Tr> <Tr> <Th> Publication date </Th> <Td> January 26, 2009 </Td> </Tr> <Tr> <Th> Pages </Th> <Td> 224 </Td> </Tr> <Tr> <Th> ISBN </Th> <Td> 978 - 0 - 393 - 35036 - 4 </Td> </Tr> <Tr> <Th> OCLC </Th> <Td> 154706867 </Td> </Tr> <Tr> <Th> Dewey Decimal </Th> <Td> 523.49 / 22 22 </Td> </Tr> <Tr> <Th> LC Class </Th> <Td> QB701 . T97 2009 </Td> </Tr> <Tr> <Th> Preceded by </Th> <Td> Death by Black Hole </Td> </Tr> <Tr> <Th> Followed by </Th> <Td> Space Chronicles: Facing the Ultimate Frontier </Td> </Tr> </Table> <Tr> <Th> Author </Th> <Td> Neil deGrasse Tyson </Td> </Tr> <Tr> <Th> Language </Th> <Td> English </Td> </Tr> <Tr> <Th> Subject </Th> <Td> Astronomy, Pluto </Td> </Tr>

According to the preface what is the main topic of the pluto files