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You are here: BBC > Science & Nature > TV & Radio Follow-up > Horizon

The Death Star
BBC Two 9.00pm Thursday 18 October 2001

Artist's impression of gamma ray burst emerging from hypernova Out in deepest space lurks a force of almost unimaginable power. Explosions of extraordinary violence, are blasting through the Universe every day. If one ever struck our Solar System it would destroy our Sun and all the planets.

For years no one could work out what was causing these awesome explosions. Now scientists think they have identified the culprit. It's the most extreme object ever found in the Universe; they have christened it a 'hypernova'.

Cold War cosmology

The mystery began in 1967. A US military satellite was launched to detect Soviet nuclear tests which the Pentagon believed were secretly taking place on the dark side of the Moon. Instead, the satellite picked up evidence of explosions far bigger than any bomb. Something was emitting bursts of gamma rays - the deadliest form of energy known - on a massive scale. What was worse, these blasts just kept on coming.

Breaking the law

For decades scientists were baffled. Especially disturbing was evidence that these explosions might be coming from the furthest reaches of the Universe, billions of light years away. If this was so, then for us to see them on Earth they had to be on a scale that was beyond our comprehension. According to some, these explosions were so huge that they might even violate the most sacred law in all science: Einstein's famous equation relating mass and energy, E=mc². That law underpins nothing less than our understanding of how our Universe works.

Live fast, die young

It was not until 1997, when a satellite pinpointed the exact location of these bursts, that scientists began to solve the puzzle. It seems these huge explosions are caused by the death throes of stars twenty times the size of our Sun, which burn themselves out and explode, creating hypernovae. What then unfolded was a chain of events, which would ultimately point towards some of the most exotic wonders in the Universe: stellar nurseries (where new stars are born) and black holes.

Observations show that - instead of fading away, as an explosion might be expected to - radiation continues to emerge from the area of a hypernova. This ongoing emission is characteristic of the process of star birth. Astronomers conclude that the hypernova grows rapidly along with other normal stars in a nursery, but burns out when its contemporaries are still in their infancy.

Pointing to the past

Find a hypernova, therefore, and you have also tracked down a part of space where stellar synthesis is underway. Which is why some scientists now believe that the huge explosions of hypernovae may be the key to unlocking one of the great unsolved mysteries in the Universe: how the first stars were made at the very dawn of time.

Read the complete transcript Jump to the Science message board BBC Science's Space site has more on this Horizon story
Find out more
Stan Woosley Stan Woosley, an astronomer from the University of California at Santa Cruz, went online after the show to discuss the programme. You can read his answers to your questions on the BBC Space site.


NASA - Gamma ray bursts
http://imagine.gsfc.nasa.gov/docs/science/know_l1/bursts.html

NASA - Pictures of star nurseries
http://antwrp.gsfc.nasa.gov/apod/stellar_nurseries.html

Space Telescope Science Institute - Hubble Space Telescope
www.stsci.edu/

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