Many types of electromagnetic waves travel through the Universe: infrared, ultraviolet, X-rays and gamma rays. Visible light, the only form of radiation perceived by the human eye, accounts for only a tiny fraction of the electromagnetic activity in the Universe.

Each celestial body propagates radiation at different frequencies, depending on its physical and chemical characteristics. The Sun, for example, in addition to visible light, emits infrared, ultraviolet and X-rays. The most powerful radiation - gamma rays -are the signature of extremely violent phenomena, such as black holes or supernovas (explosions of stars). A supernova releases more energy than the combined light of billions of stars.

When massive stars explode, at the end of their life cycle, they produce new chemical elements. Gold, iron, sodium and chlorine result from supernovas. These atoms are the building blocks for future stars and planets, meaning that human beings and all other forms of life come from the ashes of stars.

The conditions in which these new atoms are formed remain poorly understood. By detecting and analysing recent supernovas, Integral will help answer these scientific questions.

When a star explodes, the upper layers are ejected and nothing remains at the centre, except a very dense body called a neutron star or pulsar. A single cubic centimetre of its matter is the equivalent of 100 million tonnes of mass.

The bigger a star is, the more violently it explodes. When a body is four times the mass of our Sun, its matter is so contracted that nothing, not even light, can escape from it. As a result, the star becomes invisible. This is what we call a black hole.

In addition to stellar black holes resulting from supernovas, the Universe also contains much more massive black holes at the heart of certain galaxies. A giant black hole may well be concealed at the centre of our own Milky Way galaxy.

Integral's field of research is immense, because so many mysteries remain to be solved. How many neutron stars and black holes exist in our galaxy? Are there really millions of them, as many scientists believe?

Integral is also studying the unexplained gamma ray bursts observed each day by satellites. These phenomena last just a few seconds and originate in various regions of the Universe.

A catalogue of these sources, compiled from the spectrometer observations, was published in August 2005 and has since been extended. Integral has now discovered 228 objects, 20 of them of an unknown nature.

A team of scientists has shown that a significant proportion of the antimatter created in the galactic plane is generated by special types of pairs ofstars: a black hole or a neutron star whose colossal gravitational force wrenches matter away from a companion star with a mass no greater than that of our Sun.

This discovery explains half of the antimatter observed in the central bulge of the Milky Way. Scientists attribute the rest to other agents like supernovae, such as the super-massive black hole at the centre of our galaxy.