Astronomy of x-rays

The astronomy of x-rays (or also “ astronomy X ”) is the observational branch of the Astronomie which deals with the emission x-rays of the celestial objects. Since the radiation X is absorbed by the Atmosphère of the Earth, the instruments must be sent to high Altitude, in the past by balloons or rocket S. Aujourd'hui, astronomy X is part of space research and the Détecteur S of x-rays are placed in satellite .

Radiation X is produced by sources which contain extremely hot gas, with Température S of a million to several hundreds of million Kelvin S. the gas is then composed of Atome S and electron S with very high energy.

The discovery of the first cosmic source of x-rays in 1962 was a surprise. This source is called Scorpius X-1 (source X number 1 in the Constellation of the Scorpion) and is in the direction of the center of the Milky Way. According to this discovery, Riccardo Giacconi accepted the Nobel Prize of physics in 2002. Later it was discovered that this source is ten thousand (10  000) times more brilliant in x-rays than in the visible field. Moreover, the energy released by x-rays of this source is a hundred and thousand (100  000) times larger than the totality of the radiative emission of the Sun in all the wavelengths.

Today one knows that the sources of x-rays in the sky are compact objects, such as neutron stars or black holes, but also of the massive stars like stars O or Wolf-Rayet. Particularly interesting sources are the binary stars “X”, which are made up of a “normal” star (on the principal sequence, or not very far) and of a compact object. If the orbital Period is short (a few days), the normal star lose its matter in direction of the compact object, around whose accretion is formed a Disque which generates x-rays.

It was as found recently as space between the Galaxie S in the Univers is filled of a very hot diffuse bottom (Température of approximately 100 million Kelvins), similarly with the cosmological basic radiation in the field radio.

History

The first measurement were made in 1948 by the team of Friedman of the laboratory of the navy étatsunienne (US Naval Research Laboratory, NRL), with Geiger counters embarked in a V2 taken with German; they thus could detect x-rays emitted by the solar crown.

In 1962, a rocket Aerobee equipped with three Geiger counters was launched New Mexico by a team AS&E/MIT and measured the radiation of a source located apart from the solar system, Scorpius X-1.

The first extra-atmospheric telescope was embarked in the Einstein laboratory, launched in 1978. Focusing by mirrors made it possible to obtain an image. It ceased functioning in April 1981.

Let us note that x-rays are also used to analyze the rocks (Spectrométrie of x-ray fluorescence). The first apparatuses were embarked in 1976 and 1977 in the missions Surveyor V, VI and VII. More recently, that was used for the mission Pathfinder.

See too