What are stars?
Stars are hot bodies of glowing gas called Nebulae. They vary in size, mass and temperature, diameters ranging from 450x smaller to over 1,000x larger than that of the Sun. Masses range from a 20th to over 50 solar masses and surfaces temperature can range from 3,000 degrees Celcius to over 50,000 degrees Celcius.
What are they made of?
Stars are big exploding balls of gas, mostly hydrogen and helium. Our nearest Star, the Sun, is so hot that the huge amount of hydrogen is undergoing a constant Star-Wide nuclear reaction, like in a hhydrogen bomb. Even though it is constantly exploding in a nuclear reaction, the Sun and other Stars are so large and have so much matter in them that it will take billions of years for the explosion to use all the "fuel" in the star. The huge reactions taking place in stars are constantly releasing energy (called electromagnetic radiation) into the universe, which is why we can see them and find them on radio telescopes such as the ones in the DSN (Deep Space Network). Stars, including the Sun, also send out a solar wind and burst out occasional solar flares.
How is a red star different from a blue star?
The colour of a star is determined by its temperature, the hottest Stars are Blue and the coolest Stars are Red. The Sun has a surface temperarure of 5,500 degrees Celcius.
What is the first stage in the life cycle of a star?
How does a large star die?
Blue Giant Stars die in a spectacular way. They grow larger just like the Sun sized Stars, but then instead of shrinking and forming a Planetary Nebula they explode in what is called a Super Nova. Super Nova explosions can be brighter than an entire Galaxy, and can be seen from very far away.
Dead Super Giant Stars and Blue Giant Stars often turn into Black Holes. A Black Hole is a very compact object. How does this happen? As the Star dies it explodes in a huge explosion called a Super Nova. The Super Nova blasts away most of the Star. Anything left begins to fall in to the middle of the Star. It gets more and more compact, and smaller and smaller. If there is enough of the Star left after the explosion, the Star will be heavy enough to squash it down to the size of an Atom, or even smaller.