Page 8 - Curriculum Visions Dynamic Book

 The Stingray Nebula, the youngest known planetary nebula. A bright central star
is in the middle of the green ring of gas. Its companion star is at the top left.
Colours shown are actual colours emitted by nitrogen (red), oxygen (green), and hydrogen (blue).
It is thought that the gas giants (as well as the Sun and even the rocky planets) were formed from such a nebula.
For more on the life cycle of stars see Volume 1: How the universe works.
The birth of the Sun
All galaxies contain a huge amount of interstellar (“between star”) gas and dust. This material
is mainly hydrogen atoms and hydrogen molecules, which are the building blocks of
all stars.
Space contains not just the things
we can see through powerful optical or
radio telescopes. It also is made up of things
we cannot see, such as waves of radiation (energy).
It is likely that such waves of energy move right through the galaxies. You can think of these waves as
being like the ripples created in a pond when someone drops a pebble into the water. As the ripples pass by, the waves do not disturb the main features of the galaxy,
such as the stars. They are anchored in place because they are too large to be disturbed by energy waves. But the interstellar cloud is stirred much more easily by gravity waves, and its gases and dust can be made to move closer together in some places. When this happens, the gravity of the material starts to pull itself together. This sets in place a train of events that will lead to the formation of a star.
The fuel for a star
Everything about the Sun relies on one important process: the change in energy that occurs as a result of nuclear reactions within it. The main process is nuclear fusion.
In it electrons (negatively charged particles) are separated from the nucleus of the atom (which is called ionization), and then the central positively charged parts of atoms called protons fuse together. During these reactions the protons in the nuclei of hydrogen atoms fuse to produce protons of helium atoms.
It is the immense gravity inside the Sun that creates the pressure that allows fusion reactions to occur in the core. This intense reaction releases more energy per unit of mass than anything else that happens in the universe.
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