Equinox

In "The Real Death Star" a mysterious phenomenon discovered in space is investigated. In the 1960s, an American spy satellite detected mysterious bursts of intense radiation coming from deep space. The 30-year race to identify their source became the greatest detective story of modern astronomy. It recently ended in the discovery of the most violent explosions in the cosmos: events so ancient that they may signal the birth of the very first stars in the Universe, and so powerful that they are capable of destroying life on a galactic scale.

The discovery that has sent hundreds of astronomers on the greatest detective hunt in cosmology came from Eisenhower's Test Ban treaty of the late 1950s. Determined to check that the Russians weren't secretly exploding nuclear weapons on the far side of the Moon, the Americans ordered a brilliant Los Alamos engineer, RAY KLEBASADEL, to design a network of orbiting gamma-ray detectors to alert them to clandestine Soviet explosions in space. But when his satellites started to pick up intense bursts of gamma-rays, Klebasadel soon realised it wasn't the Russians - it was something far more powerful.

For several years the bursts were known only to the scientists at Los Alamos. When they were finally made public in the early '70s, they became the biggest mystery in astronomy, and the subject of a 30-year scientific race that made and destroyed a number of scientific careers. The enigma of the gamma-ray bursts (GRBs) was compounded by the fact that they came from all directions, yet when astronomers trained their telescopes to where the bursts were coming from, there was nothing there.

The first scientist to grasp the implications of these two facts was Polish astronomer BODAN PACZCYNSKI. He suggested that the bursts were coming from the edge of the observable universe, that they were in the parlance, "cosmological". This seemed impossible to most scientists, because if they were so distant then they must be incredibly powerful - a billion billion times brighter than the Sun. Leading US astronomer DON LAMB was convinced that they must in fact coming from the vicinity of the Earth, from a cloud of invisible neutron stars that he thought might fill the galaxy.

In the end it became clear that PACZCYNSKI was right and LAMB was wrong. GRBs are not local, they occur in galaxies across the entire Universe. And they are stupendously powerful. When they explode, they briefly outshine all the stars in all the galaxies in the entire universe! Astronomers now believe that GRBs happen when a super-massive star collapses to form a black hole in a so-called "hypernova". The gamma-rays are emitted in a narrowly-focused beam, a real-life death ray. A thousand GRBs explode every day, and Israeli scientist ARNON DAR thinks that the Earth may have been hit by these rays many times in its history, triggering some of the mass extinctions which punctuate the fossil record. He even suggests that GRBs explain why space is not filled with aliens. GRBs are violent enough to sterilize entire galaxies, destroying alien civilisations before they can spread.

But for most astronomers, the excitement of GRBs is that as the brightest light sources in the cosmos, they shine across space and time from the very beginnings of the Universe as we know it, illuminating the birth of the very first stars to shine.