ASTRON 1101 Lecture Notes - Lecture 20: Cno Cycle, Kilogram, Brown Dwarf
13 Oct 2016
School
Department
Course
Professor
Document Summary
In addition to stars, our galaxy also has low-density interstellar gas in the space between stars. Sometimes, this gas is visible as a nebula (latin for cloud ) with an emission-line spectrum. The interstellar gas in the orion nebula is hot because it is heated by four luminous stars (called the trapezium) The four stars of the trapezium are main sequence stars with m > 10 msun. Thus, they have nuclear time scales tnuc < 10 million years. The trapezium stars formed from lower-density gas around the orion nebula less than. Star formation is an ongoing process in our galaxy. The raw material for star formation is provided by giant molecular clouds. Density: 104 molecules/cm3 (on average: in the air around you: 3 (cid:883)(cid:882)19 molecules/cm3, in most of interstellar space: <1 atom/cm3. Giant molecular clouds are barely stable against collapse. They are supported by a mix of gas pressure, turbulence, and magnetic fields.
