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An Astronomer’s Guide to the Extreme Cosmos

University of Sydney News | 2 September 2011

Prof Bryan Gaensler speaking at the launch of his book 'Extreme Cosmos'
Prof Bryan Gaensler speaking at the launch of his book 'Extreme Cosmos'

By Kath Kenny

AS A CHILD, Professor Bryan Gaensler played cricket and rugby during the day, while at night he peered through a tiny telescope, spying the craters on the Moon or the rings of Saturn.

This is how the editor of COSMOS magazine, Wilson da Silva, described the young Bryan Gaensler - now an internationally lauded astronomer and Australian Laureate Fellow at the University of Sydney - when Professor Gaensler’s book Extreme Cosmos was published this week.

It is his first published book, because Gaensler’s first book was actually another about astronomy, written at the age of seven after his schoolteacher, exasperated at his constant questions about the heavens, challenged him to write a textbook for the library.

“When I was 12, I used my pocket money to buy a telescope and stayed up all night to watch Halley’s Comet,” Gaensler writes in the introduction to Extreme Cosmos. It is an always fascinating and sometimes dizzying tour through the extremes of the known Universe - the hottest stars and fastest planets, the biggest and heaviest objects, the loudest, densest and coldest places.

Extreme Cosmos introduces us to the Universe’s largest known star - a hyper-giant with the seemingly appropriate name of WOH G64. With a diameter of two billion kilometres, if WOH G64 was a basketball, our Sun wouldn’t even be a dust mite, Gaensler helpfully explains.

Gaensler also dazzles us with unimaginable numbers such as 300 sextillion: a three followed by 23 zeros, and the total number of stars in the observable Universe.

And he asks you to turn your mind to a temperature of five billion degrees Celsius: the temperature of a star towards the end of its life, when its largely iron core has collapsed to become a ball of neutrons with a diameter of just 25 kilometres.

As you read you realise your good fortune in having a guide such as Gaensler. For as da Silva explains: “Bryan is one of those rare combinations: a passionate scientist who is pushing back the frontiers - making real advances in his field - but who can also write beautifully.”

Gaensler writes, for example, of the beginning of life on Earth, which started when “molecules rained down onto the young Earth by a bombardment of asteroids”.

In an almost matter of fact voice he explains how “we are all made of the ashes of ancient supernovas”. And you won’t miss the passion behind his description of the night sky on country trips: “The glitter of bright stars, the patterns of the various familiar constellations, and the broad glowing band of the Milky Way can be dazzlingly bright.”

When curious six or seven-year-olds picked up Gaensler’s early textbook in his old school library, they no doubt have wondered: what is the biggest, fastest, hottest, or brightest thing in our Universe?

Extreme Cosmos is the book written when that boy grew up and never stopped asking himself those questions, wondering what else was out there.

“I want to convey to you just how far beyond our everyday experience the Universe extends in every imaginable way,” Gaensler writes. And that is exactly what he does. No wonder da Silva describes him as Australia’s Carl Sagan.

Bryan Gaensler is an award-winning astronomer, internationally recognised for his ground-breaking work on dying stars, interstellar magnets and cosmic explosions. A former Young Australian of the Year, NASA Hubble Fellow and Harvard professor, he is currently the Director of the Centre of Excellence for All-sky Astrophysics at the University of Sydney.

Extreme Cosmos is published by NewSouth Publishing.


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