Previously, you will have met the Big Bang Theory. In this section, you need to know that just after the "bang" we believe that the temperature began to fall and the lightest elements, hydrogen and helium, formed. As all things with mass have gravity, the particles and dust clumped together, following a theory called accretion, and different galaxies were formed. If there was enough mass, the gravity caused heat and a star burst into life. Jupiter is almost massive enough to be known as a "brown star", not massive enough to complete fusion reactions like our sun, but would be able to complete some. In our galaxy, the milky way, there are billions of stars. Our galaxy is mainly empty space, millions of miles between planets and millions of millions of miles between stars.

I know that I will not win an award for the graphics, but the point is shown. In a nebula or protostar, there is a cloud of hydrogen and helium that will accrete and form a star. If it is very massive, after finishing its time as a main sequence star, it will swell to become a red supergiant then explode to either form a neutron star or if heavy enough, a black hole. Likewise, if the main sequence star is not a high mass star, it will swell to form a red giant then after the fuel has run out, it will become a white dwarf which will eventually cool, after billions of years to become a black dwarf.

The last point in this topic and indeed in this science syllabus is perhaps the most profound. All elements other than hydrogen and helium were manufactured by the fusion process. Lighter elements were fused together to make heavier ones and that process releases the energy in stars. Elements that have an atomic number equal to or higher than that of Iron are only formed in the final stages of a massive dying star. When that dying star became a super nova, its elements were fired across the galaxy. As the inner planets of our solar system have lots of iron and heavier elements, they were made from the debris of a super nova.
This leads me to the final point, when we gave these badges out at the school where I work, this was not a cute message, it was a scientific fact. We are all made from elements that were created in a dying star!

Key words and terms for this topic: gravitational attraction, star, protostar, main sequence star, red giant, white dwarf, black dwarf, supergiant, neutron star, black hole.

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