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The Explosion that Rocked the Universe

By David Reneke

The launch of a revolutionary Australian instrument will enable the fastest-ever survey of stars in our galaxy.

It was one of the most powerful explosions ever seen, and it echoed right across the visible universe. Recently, an international team of 31 astronomers, led by the University of Maryland’s Eleanora Troja and Nathaniel Butler from Arizona State University, caught a massive star as it died in a titanic explosion deep in space.

The blast of the dying star released in about 40 seconds as much energy as the Sun releases over its entire lifetime, all focused into a tight beam of gamma rays aimed by chance toward Earth. The team’s findings, using two purpose-built NASA satellites, provide strong evidence for one of two competing models for how gamma-ray bursts produce their energy. These are the brightest explosions in the universe, allowing astronomers to record the development and decay almost from the initial blast. The satellite observatories detected the burst of gamma rays, identified where in the sky it came from, and sent its celestial position within seconds to automated telescopes on the ground.

While gamma-ray bursts have been known for about 50 years, astronomers are still mostly in the dark about how they erupt. “Despite a long history of observations,” Butler says, “the emission mechanism driving gamma-ray bursts remains largely mysterious, but the magnetically driven model is gaining favour”.

Gamma-ray bursts are detected approximately once per day and are brief, but intense, flashes of gamma radiation. They come from all different directions in the sky, and they last from tens of milliseconds to about a minute, making it hard to observe them in detail.

Astronomers believe most of these explosions are associated with supernovas. These occur when a massive star reaches the end of its normal existence and blows up in a colossal explosion. A supernova throws off some of the star’s outer layers, while its core and remaining layers collapse in a few seconds into a neutron star or, in the case of highly massive stars, a black hole.

Continued observations over weeks following the outburst showed that the gamma rays were shot out in a beam about 2° wide, or roughly four times the apparent size of the Moon. It was sheer chance that Earth happened to lie within the beam.

The large amount of polarisation the team observed indicates that powerful magnetic fields were confining and directing it. This lends support for the magnetic origin model for gamma-ray bursts.

While gamma-ray bursts have many more mysteries to solve, Butler says that “this is the first strong evidence that the early shocks generated by these bursts are magnetically driven”.


Starlight, Star Bright, First Star I See Tonight

How many stars are there in our Southern Hemisphere skies? As impossible as it sounds, progress towards an answer is being made in our own backyard. University of NSW scientists will co-lead the fastest-ever survey of stars in our galaxy, following the launch of a revolutionary Australian instrument that can observe more than a million stars per year.

The $7 million TAIPAN instrument, which contains 150 mini-robots called “Starbugs” that rapidly and accurately align the optical fibres of a telescope to target stars and galaxies, was launched recently by the Assistant Minister for Science, Jobs and Innovation, Zed Seselja.

Designed by the Australian Astronomical Observatory (AAO) and installed on the UK Schmidt Telescope at Siding Springs Observatory near Coonabarabran in NSW, TAIPAN will allow astronomers to make new discoveries about dark energy, dark matter, and galaxy and star formation and evolution.

“TAIPAN technology is revolutionary because it allows all 150 Starbugs to independently move to new targets, saving enormous amounts of time,” said UNSW astronomer Prof Chris Tinney, co-leader of the stellar survey.

Astronomers will be able to observe a new set of 150 stars every 6 minutes. That means about 15,000 stars per night, or more than a million stars per year, making it the fastest survey of stars in our galaxy ever obtained. From the observations, the team will create a detailed spectrographic database for millions of stars in the Southern Hemisphere.

“This will allow us to search for new planetary systems. We will be able to identify the youngest stars – the stellar nurseries where young planets have recently been born,” Tinney said. It will provide us with an unprecedented map of the structure, history and future of our home, the Milky Way.

The Taipan galaxy survey will be the most comprehensive spectroscopic survey of the Southern Hemisphere ever undertaken and will, for the first time, measure the current expansion rate of the universe to 1% accuracy. The survey will also determine both the age and size of the Universe with extraordinary precision.


David Reneke is an astronomy lecturer and teacher, a feature writer for major Australian newspapers and magazines, and a science correspondent for ABC and commercial radio. Subscribe to David’s free Astro-Space newsletter at www.davidreneke.com