24 SEP. 2002
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When a massive star explodes, not all the material is ejected into space. Some of it collapses into an extremely compact object known as a neutron star, inside which gravitational forces crush protons and electrons together, turning them into particles known as neutrons.
A neutron star contains a few solar masses of material squeezed into a radius of only 20 km. This means the matter is so compressed that a thimble full of it would weigh millions of tonnes on Earth. Fast-spinning neutron stars, whose radio emissions seem to pulse on and off, are called pulsars.
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A neutron star
Beyond the mass limit of a neutron star – about three solar masses – gravity becomes overwhelming and collapses the star even further, creating a black hole. These are perhaps the strangest objects in the Universe because nothing, not even light, can escape from inside a black hole. So, the presence of a black hole can only be inferred by its effect on surrounding celestial objects and other interstellar material.
Virtually all types of compact objects are significant sources of high-energy emission because of the enormous gravitational fields they tend to generate. Gravitational fields can accelerate particles in the vicinity to extreme velocities, which then emit gamma rays and X-rays.
During its 22 years of observations in space, Integral captured images of the high-energy emission from such compact objects with unprecedented detail, allowing astronomers a clearer look than ever before at these enigmatic objects.
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Integral overview
Name: Integral (International Gamma-Ray Astrophysics Laboratory)Status: Completed (launched on 17 October 2002, stopped collecting scientific data on 28 February 2025)Mission theme: Tracking violent events across the Universe
Integral science highlights
The International Gamma-Ray Astrophysics Laboratory (Integral) has provided unprecedented information about the Universe’s most exotic objects. It has revealed how matter behaves under extreme conditions and helped astronomers understand processes such as the formation of new chemical elements and mysterious gamma-ray bursts. These findings have been documented in an impressive, and growing, body of scientific and popular literature.
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