Stephen Smartt may one day receive a message that will give him an advance warning that one of the most extraordinary displays known to science is about to light up the night sky. A star in our neighbourhood has just turned into a supernova.
A supernova happens when a star destroys itself so completely that it can't see anything else. Only five have been visible to the naked eye in the last thousand years. All occurred before the invention of the telescope.
Smartt, an astronomer based at Queen's University Belfast, says that we know about supernovae from their appearance in other galaxies and from remnants left behind in our own galaxy.
If a supernova went off within 10 parsecs of our planet, it would be very likely to cause a mass extinction
When a supernova erupts, it sprays the universe with heavy elements so that we can learn more about the creation of matter in our galaxy.
Most elements heavier than oxygen were created in a supernova before being flung across space. The gold in the ring on your finger and the calcium in your bones were created in supernovae explosions.
It is an image that attracts writers and artists. Astronomers have shown that our first parent was a star and that we are made of elements that are radioactive from the supernova bang. "We are stardust", as Mitchell put it.
The most common type of supernova happens when a large star runs out of fuel and the fusion process fails. The star's outer layers fall inwards, and protons and electrons are crushed together to form neutrons that are packed into a super dense ball. The star is destroyed by a shock wave when matter continues to rain down on it.
A matchbox of a neutron sphere is so dense that it would weigh 3 billion tonnes. If the progenitor star that led to the supernova was large, it will form a black hole so dense that nothing can escape, not even light.
This is a core-collapse supernova and it can unleash more energy than our sun can. If a star in our galaxy becomes a supernova, it will shine so bright that it can be seen in daylight.
Scientists estimate that there are about 20 supernovae in ours every thousand years. In the last millennium, only five have been observed. European documents recall the events of 1572 and 1604 while records from East Asian and Arabic show that there were supernovae in 1006, 1054 and 1181.
Tycho Brahe observed the first of the last pair in November 1572 and it was a strange star.
Why have we only detected five supernovae in the past 1000 years? We haven't seen a number that is close to the 20 suggested by other telescopes. Sullivan says the answer is simple. A supernova that occurs on the other side of the plate will be obscured by all the stars and dust in the centre of the galaxy.
Astronomers have studied the remnants of supernovae that occurred inside our galaxy. The Crab Nebula, the remains of a supernova that lit up night skies in 1054AD, are included.
The enormous destruction that is unleashed by supernovae can be seen in the debris. Scientists argue that stellar convulsions are important engines of creation. They also play a key role in planet and star formation, according to Cosimo Inserra.
A supernova causes shock waves across a galaxy and these strike clouds of gas and dust in space to cause the formation of stars. Nuclear fusion begins when a star has a store of hydrogen. Planets form and travel around the star. That is how the sun and solar system came to be.
If one occurred within 20 parsecs of the Earth's surface, its intense Cosmic rays could destroy our protective ozone layer, which would allow increased levels of ultraviolet radiation. Only one very close to Earth could have such an impact and there are no candidate stars near us that are ready to do it.
It is clear that there have been supernovae near Earth in the past. Scientists point to the discovery of a radioactive isotope of iron in some of the deposits that were created about 7m years ago. The deposits of iron-60 suggest that at least two must have erupted near Earth within the last 10m years.
Prof John Ellis of King says that it is not certain what impact a rise in Cosmic-ray activity had on the planet.
There is a chance that the appearance of Homo sapiens might have been shaped by local supernovae, but these discoveries also suggest that there was more than one.
If you find two that happened within the past 10m years, that suggests hundreds have appeared over the past billion years. If a supernova went off within 10 parsecs of our planet, it would cause a mass extinction.
At least five mass extinctions have each wiped out thousands of species of animals, plants and sea creatures, and at least one of these was caused by an extraterrestrial agent.
Large-scale volcanism has been blamed for the other mass extinctions. Scientists think that an event was to blame in one of the cases. There was a mass extinction that wiped out ammonites, trilobites and other early forms of life at the end of the Devonian period.
The evidence of a long-term ozone-depletion event can be seen in the hundreds of thousands of generations of plant spores found in these rocks.
The blast would have unleashed powerful X-rays and gamma rays on Earth, before debris from the blast ripped the ozone layer off the planet. The planet's surface would have been exposed to deadly radiation for up to 100,000 years, leading to a mass extinction.
Scientists are looking for proof of this idea. They have discounted looking for iron-60 atoms because they decay too quickly. They plan to look for plutonium-244, which is produced by supernovae and could survive for a few hundred million years. The research is under way.
Scientists are ready to react quickly to the first signs of a nearby supernova. The first signals will not come from light, but from underground detectors that will spot the most insignificant entity in the universe.
Neutrinos are the first thing that will emerge from a supernova and are very difficult to detect.
If enough are detected, an automated alert will be sent out and the array of telescopes that we use to study the night sky will be turned towards the sources of those neutrinos. We will study the first bursts of radiation and light from the supernova and watch how it unfolds.
Scientists are confident that a supernova will occur in the future, but it is not certain if it will happen in our galaxy. It is not likely in any given year. One day it may happen in our neighbourhood. Astronomers say they will be ready if it does.
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