New eye on the sky

3 November 1998

A new satellite is nearing completion that will give astronomers an unprecedented view of the
violent activity around black holes,
starquakes and
other strange phenomena.
The International Gamma Ray Astrophysics Laboratory (Integral) will have a resolution 10 times better than current facilities of its kind.

The European Space Agency (ESA) plans to launch the
satellite in April 2001 and
use it to study hard X-ray and
gamma-ray sources in the
energy range 15 keV to 10 MeV.
A full-scale structural and
thermal model of the
telescope has just been completed ready for testing.

There will be two main instruments on board. A spectrometer made of high-purity germanium will measure gamma-ray energies extremely precisely whilst an imager will record their position in the sky.

With a resolution of 12 arc-minutes it is the imager that excites astronomers the most. Current telescopes,
such as NASA’s Compton Gamma Ray Observatory,
have difficulty pinpointing the source of gamma-ray emissions sufficiently to match them up with objects seen at other wavelengths.

A breakthrough came last year when the
Italian Bepposax X-ray satellite identified the
origin of a gamma ray burst.
The observations showed the
burst came from a galaxy towards the
edge of the
visible universe and
must therefore be incredibly energetic ­ way over 1050 ergs,
more than the
energy released by all the
1011 stars in our Galaxy over several days! The mechanism fuelling gamma-ray bursts remains a mystery that astronomers hope Integral will help to solve.

Astronomers will also use Integral to study active galaxies and,
nearer to home,
to see close up to the accretion discs surrounding black holes.

Integral’s spectrometer will be used to measure the emission lines of heavy elements ejected into space by the supernova explosion at the end of a heavy star’s lifetime.

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