Portal:Radiation astronomy/X-ray astronomy article/1

X-ray astronomy by sounding rocket uses a sounding rocket to carry an X-ray detector to high altitudes. The first evidence of X-rays from the Sun and of an X-radiation source from the Milky Way, other than the Sun, was detected by a sounding rocket. These rockets have contributed significantly to our understanding of the Sun, the solar system, and the universe as a whole.

In astronomy, the interstellar medium (or ISM) is the gas and dust that pervade interstellar space: the matter that exists between the star systems within a galaxy. It fills interstellar space and blends smoothly into the surrounding intergalactic space. The interstellar medium consists of an extremely dilute (by terrestrial standards) mixture of ions, atoms, molecules, larger dust grains, cosmic rays, and (galactic) magnetic fields. The energy that occupies the same volume, in the form of electromagnetic radiation, is the interstellar radiation field.

Of interest is the hot ionized medium (HIM) consisting of coronal gas at 106-107 K which emits X-rays. The ISM is turbulent and therefore full of structure on all spatial scales. Stars are born deep inside large complexes of molecular clouds, typically a few parsecs in size. During their lives and deaths, stars interact physically with the ISM. Stellar winds from young clusters of stars (often with giant or supergiant HII regions surrounding them) and shock waves created by supernovae inject enormous amounts of energy into their surroundings, which leads to hypersonic turbulence. The resultant structures – of varying sizes – can be observed, such as stellar wind bubbles and superbubbles of hot gas, seen by X-ray satellite telescopes. The Sun is currently traveling through the Local Interstellar Cloud, a denser region in the low-density Local Bubble.