The invisible universe

posted by @ulaulaman about #x-ray #astronomy #riccardogiacconi #universe #exhibition #milano
Today will be open in Milano an exhibition about the x-ray astronomy in order to celebrate the discover of the first cosmic x-ray source in 1962. And today I try to resume the story of this research.
The beginning of this branch of the astronomy is in 1946 when Bruno Rossi, who has worked with Enrico Fermi during Manhattan project, started to deal with physics of cosmic rays while teaching at MIT about X-ray. In 1958, with the birth of the American Science & Enginnering (AS&E), Bruno Rossi joined it as chairman of the board of directors and scientific advisor and a year later he called to work even Riccardo Giacconi. One of the first experimental successes includes the launch of the first rocket equipped with detectors for X-rays in 1962. The team of this project as well as Giacconi included, Herb Gursky, Frank Paolini, and Bruno Rossi. With this mission, it was reported the first cosmic X-ray source outside the sun, Scorpius X-1 in the constellation Scorpius.(1, 2)
The uniqueness of the observations of Scorpius X-1 is due mainly to its properties. In fact, while the X-radiation from the sun has an intensity that is approximately 10-6 times than visible light, Scorpius X-1 has a X-brightness that is 103 times higher than its same brightness in the visible light. It was subsequently discovered that its intrinsic brightness is 103 times that of the Sun!(1)
There was therefore in front of the discovery of new celestial objects, which had X-rays produced in different physical processes compared to the processes made in the laboratories of the Earth, since their efficiency (99.9%) was unmatched!(1)
1960s were, therefore, rich for X-rockets into space, but for the very first X-satellite was launched only in 1970 thanks to a new group leaded by Giacconi(1):
The X-ray astronomy achieved great success with the launch of the first satellite dedicated to X-rays, Uhuru, launched in 1970, with it performed an initial mapping of the X-ray sources in space. It was discovered that the universe is full of objects that emit X-rays, from the black holes to the pulsars, to the binary stars. In fact after this mission, the X-ray astronomy assumes an important role between the international scientific community. It soon became clear that, in order to better understand the secrets of the sky, instead of simply detecting the X-rays, it would be useful to make observations with a telescope sensitive to X-rays. The development of this telescope began with the entry into AS&E team of Giuseppe Vaiana, who leaded the program about the solar X-ray astronomy and the construction of the first telescope. In 1973, Skylab was launched, the U.S. space laboratory directed by Vaiana, that, in addition to various scientific experiments, carried on the observation of the Sun and the corona in X-rays. In 1978 it was sent into orbit the Einstein Observatory, the first X-ray space telescope. The important discoveries of the ROSAT and Chandra followed.(2)
One of the successive results of astronomy X, always signed Giacconi, in this case with Ethan Schreier, was the discovery of an X-ray source around Cen X-3(1).
Very important discoveries of Uhuru, however, were mainly those concerning the existence of neutron stars and binary systems consisting of a visible star and an unseen companion, a black hole(1)!
An equally important observation with strong implications for cosmology, however, was the recognition of an intergalattic emission between clusters of galaxies:
This emission is not simply due to the sum of the emission from individual galaxies, but originates in a thin gas which pervades the space between galaxies. This gas was heated in the past during the gravitational contraction of the cluster to a temperature of millions of degrees and contains as much mass as that in the galaxies themselves.(1)
In the last 50 years the X-ray astronomy has opened the door to a universe otherwise invisible with the usual tools, those that work with the visible light. Therefore its importance has been and continues to be crucial in astronomical research:
The reason is that this radiation reveals the existence of astrophysical processes where matter has been heated to temperatures of millions of degrees or in which particles have been accelerated to relativistic energies. The x-ray photons are particularly suited to study these processes because they are numerous, because they penetrate cosmological distances, and because they can be focused by special telescopes. This last property signi´Čücantly distinguishes x-ray from -ray astronomy. However, in a more fundamental way, high energy astronomy has great importance in the study of the Universe because high energy phenomena play a crucial role in the dynamics of the Universe.(1)

The exhibition was a combination between scientific posters, models of satellites, and some artistic interpretations of the Universe given by the students of the local Academy of Fine Arts. In the following slideshow I present a little preview of these operas:

(1) Giacconi, R. (2003). Nobel Lecture: The dawn of x-ray astronomy, Reviews of Modern Physics, 75 (3) 1010. DOI: 10.1103/RevModPhys.75.995 (pdf)
(2) Translation from
Riccardo Giacconi winned Nobel Prize in Physics in 2002
for pioneering contributions to astrophysics, which have led to the discovery of cosmic X-ray sources

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