Interstellar



Interstellar space is the physical space within a galaxy not occupied by stars or their planetary systems. The contents of interstellar space are called the interstellar medium. The average density of matter in this region is about 106 particles per m3, but this varies from a low of about 104 – 105 in regions of sparse matter up to about 108 – 1010 in dark nebulae. Regions of star formation may reach 1012 – 1014 particles per m3 (as a comparison, Earth's atmospheric density at sea level is on the order of 1025 particles per m3[100]). Nearly 70% of the mass of the interstellar medium consists of lone hydrogen atoms. This is enriched with helium atoms as well as trace amounts of heavier atoms formed through stellar nucleosynthesis. These atoms can be ejected into the interstellar medium by stellar winds, or when evolved stars begin to shed their outer envelopes such as during the formation of a planetary nebula. The cataclysmic explosion of a supernova will generate an expanding shock wave consisting of ejected materials.

A number of molecules exist in interstellar space, as can tiny, 0.1 μm dust particles. . Large regions of higher density matter known as molecular clouds allow chemical reactions to occur, including the formation of organic polyatomic species. Much of this chemistry is driven by collisions. Energetic cosmic rays penetrate the cold, dense clouds and ionize hydrogen and helium, resulting, for example, in the trihydrogen cation. An ionized helium atom can then split relatively abundant carbon monoxide to produce ionized carbon, which in turn can lead to organic chemical reactions.

The local interstellar medium is a region of space within 100 parsecs (pc) of the Sun, which is of interest both for its proximity and for its interaction with the Solar System. This volume nearly coincides with a region of space known as the Local Bubble, which is characterized by a lack of dense, cold clouds. It forms a cavity in the Orion Arm of the Milky Way galaxy, with dense molecular clouds lying along the borders, such as those in the constellations of Ophiuchus and Taurus. (The actual distance to the border of this cavity varies from 60 to 250 pc or more.) This volume contains about 104–105 stars and the local interstellar gas counterbalances the astrospheres that surround these stars, with the volume of each sphere varying depending on the local density of the interstellar medium. The Local Bubble World contains dozens of warm interstellar clouds with temperatures of up to 7,000 K and radii of 0.5–5 pc.

When stars are moving at sufficiently high peculiar velocities, their astrospheres can generate bow shocks as they collide with the interstellar medium. See also Micro Matter - Interstellar Matter ==Union and Interstellar space== Interstellar space between Union stars is considered Union or Federal space. The notion or idea that space beyond the heliopause of a star system could be claimed as sovereign territory was first introduced as a concept by the Kermac during the formation of the First Galactic Council. The Kermac declared an entire region of space as theirs and denied by threat of force anyone access without expressed Kermac consent.The concept was adopted by the Nul and then by all spacefaring societies..As the Union was founded by combining United Earth, Saran and Pan Saran space the  gaps between those territories were to distant to define a homogenous Union space. Which gave rise to the "A Union presence on every rock " policy of expansion. But even today there are Union space territories that are not connected to the Contiguous Union space in the Upward sector of the M-0 galaxy. This is due to the addition of other cultures that are not within the Upward Sector (Such as the Klack, the Attikan Commonwealth , the Arboro Community and the regions in the Andromeda Galaxy and many others) This gave rise to the corridors and connectors of narrow tunnels of space through which these regions are connected to Union Core space.