Astronomer David Grennan and his wife Carol were about to turn in from their garden shed observatory in Raheny in Dublin on 17th September when they discovered a supernova. The explosion that caused the burst of light occurred an estimated 290 million years ago. The discovery was confirmed officially by International astronomers earlier this week.

Supernovae can outshine entire galaxies for a short time, and they are the major source of heavy elements in the Universe. They can occur when a large star — much bigger than our sun — accumulates material from a nearby star, becoming massive and unstable until the energy of nuclear fusion in its core is sufficient to cause a cataclysmic explosion destroying any nearby planets or suns. Another type of supernova collapses after losing material to its neighbors. After the explosion the star collapses inwards to produce a dense, cold remnant that may become a neutron star or a black hole.

Mr Grennan is a software developer by day, but at night he spends as much time as the Irish weather permits in his home-made observatory, which is a converted garden shed with a retractable roof. Grennan said he had been stargazing since he was about five years old, and had always been fascinated by the stars. He bought his first telescope in 1991, and has continually upgraded his equipment. In 2005 he built his home observatory using standard DIY parts. The observatory is equipped with a 14 inch Cassegrain telescope.

David's wife Carol analyzes the images he takes with his telescope and helps identify interesting objects. They discovered the supernova by comparing images of the galaxy UGC 112 taken in August and September. The signs were tiny, but David’s many years of experience helped him to spot them.

David said the discovery was the result of a year’s work, during which he surveyed 2,611 galaxies. He said it was “mind-boggling” to be the first to see something that happened almost 300 million years ago, and the time-lag “is on a scale almost as difficult to comprehend as Ireland’s astronomical debt.” Carol was even more excited than he was, and the two shared a bottle of champagne when the supernova was confirmed.

The supernova, named 2010 IK by official astronomy bodies, is the first to be discovered by someone in Ireland, but it is not Grennan’s first discovery. In 2008 he discovered a three-meter-wide asteroid (his second), which he named after his mother, Catherine Griffin, in honor of her encouragement of his stargazing hobby.

Grennan, who was once chairman of Astronomy Ireland, said he would love to see young children becoming interested in astrophysics because “it’s amazing what you discover.”

Supernovae are spotted regularly, but Professor Stephen Smartt of Queen's University Belfast said it was unusual for astronomers in northern Europe to find one. He confirmed the finding was the first supernova to be discovered from Ireland.

The supernova is expected to be visible with a powerful telescope for the next two or three months, after which it will fade from view.