Astronomy Notes Chapter 2
Birth of Stars....Lives of Stars
Interstellar
-This is gas and dust that occupy space between the stars
-Stars form out of the gas/dust in space
-Clouds are lightyears across
-When a star is born there is a high wind that blows off particles and then the star can then
appear
Dust
-Dust is approx 1% of the total visible mass is space
-Obscures our view of distant objects in the galaxy
-What is the dust?
It is a mixture of
-Elongated, tiny grains of dirty ice
-Grains of graphite (carbon)
-Silicate particles (comes right under carbon in periodic table therefore it has the same
chemical properties as carbon)
-Complex molecules
Interstellar Reddening
-Light from a star passes through the dust cloud
-The dust particles are approx the same length as blue wavelengths
-The dust scatters blue wavelengths more than red wavelengths
-Red wavelengths go right through the dust particles but the blue wavelengths have trouble,
and is therefore scattered
-A larger number of red photons pass unhindered through the dust and reach the observer
-Star appears redder than it actually is
Gas
-There is approx 100 times more gas mass than dust mass in the universe
-Gas/Dust is approx 100
-We can only detect 4% of the universe
-The visible universe contains *** Test Question
75% hydrogen
24% helium
<1% other
H1 Regions
-These are clouds of neutral (=NOT ionized) Hydrogen. There are the same number of
protons as electrons
-Atom is ionized if you take one or more electrons
- Contains approx 1 Mo to approx 100 Mo
-The cold hydrogen gas is in its ground state (n=1 orbit). It is in its first permitted orbit
-Protons and the electron are either spinning together or opposite from each other. This
spinning gives us an indication of ............
-The hydrogen atom has TWO possible ground state configurations
-Parallel spin or aligned spin (same direction) which takes more energy. When it changes
direction it is known as a spin flip
-When it performs a spin flip that excess energy must give off its radiation as a burst of
energy
-The electron can undergo a spontaneous “spin flip” from the aligned (=parallel) state to the
opposed (anti-parallel state)