Riccardo Giacconi (2004) - X-Ray Astronomy

Riccardo Giacconi (2004)

X-Ray Astronomy

Riccardo Giacconi (2004)

X-Ray Astronomy

Abstract

In 1959, after teaching at the University of Milano and spending a Fulbright Fellowship at the Universities of Indiana and Princeton, I joined American Science and Engineering, a private 30 person corporation in Cambridge, Massachusetts. There I started a group to develop space science initiatives, particularly in x-ray astronomy (which can only be carried out from space). We developed new detectors and techniques that permitted us to discover the first x-ray star during a rocket flight in 1962, carried out under the sponsorship of the US Air Force. The detection of this star required an improvement of the techniques used up to then, by a factor of 100.

The star system we had observed was of extraordinary astronomical interest. It represented a new class of celestial objects previously unknown, a thousand times more luminous than the sun and emitting 99.9% of its energy in x-rays by some unknown process.

This finding stimulated the development of more sophisticated satellite-born instrumentation, under NASA sponsorship, which culminated in 1970 with the launch of a satellite “UHURU”, a 1000 times more sensitive than the rocket experiment (Fig. 1.). With this satellite more than 300 x-ray sources were discovered (Fig. 2).

To summarize the findings;
• We found the first x-ray binaries, normal stars with a neutron star or a black hole companion (Fig. 3);
• We found a hot (millions of degrees) gas pervading the spaces between galaxies in clusters, containing more mass than the galaxies themselves. We realize now that this gas may provide most of the normal matter in the universe;
• We found the first x-ray emitting galaxies and quasars containing super massive black holes.

These findings changed our view of the Universe and underlined the importance of high-energy observations to all of astronomy. This in turn, stimulated further technical development. The concept of an x-ray telescope initiated at ASE in 1959 and developed by the corporation for more than twenty years came to fruition as a NASA facility costing more than 1 billion dollars. The satellite CHANDRA was launched in 1999 (Fig. 4) and can see sources in the Universe a
billion times fainter than the star first discovered in 1962 with an angular resolution comparable to that of the best optical telescopes (Fig. 5).

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