What is a Stars? | Types, Definition, Structure, Function & Facts
What is a Star?
Stars are giant balls of superheated gas composed mainly of hydrogen and helium. Stars become so hot by burning hydrogen to helium in a process called nuclear fusion. That’s what makes them so warm and shiny. Our sun is a star.
Lifecycle of a Star
Birth – Stars are born in huge clouds of dust called nebulae. Gravity forces dust to clump together. As more and more dust accumulates, gravity becomes stronger and it begins to heat up and become a protostar. Once the center is hot enough, nuclear fusion will begin and a young star is born.
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Main Sequence Star – Once a star, it will continue to burn energy and shine for billions of years. This is the state of the star for most of its life and is known as the “main sequence”. During this time, a balance occurs between the gravity that wants to shrink the star and the heat that wants to make it grow. The star will stay that way until it runs out of hydrogen.
Red Giant – When the hydrogen runs out, the star’s exterior expands and becomes a red giant.
Collapse – Eventually, the star’s core will begin to produce iron. This will cause the star to collapse. What happens to the next star depends on its mass (how big). The average star will become a white dwarf. Larger stars will create an extremely large nuclear explosion called a supernova. After the supernova, it can become a black hole or a neutron star.
Types of Stars
There are many types of stars. The stars in their main sequence (ordinary stars) are classified by their color. The smaller stars are red and don’t shine as much. Medium-sized stars are yellow, like the Sun. The largest stars are blue and extremely bright. The larger the main sequence star, the hotter and brighter it is.
Dwarfs – Smaller stars are called dwarfs. Red and yellow stars are often called dwarfs. A brown dwarf is a dwarf that is never large enough for nuclear fusion to occur. A white dwarf is a remnant of the collapse of a red giant star.
Giants – Giant stars can be main sequence stars such as blue giants or developmental stars such as red giants. Some supergiant stars are as big as the entire solar system!
Neutrons – A neutron star created from the collapse of a massive star. It is very small, but very dense.
Interesting facts about Stars
They flicker due to motion in the Earth’s atmosphere. Many stars that go in pairs are called binary stars.
Some groups have up to 4 stars.
The smaller they are, the longer they live. Giant stars are very bright, but tend to fade quickly.
The closest star to Earth is Proxima Centauri. It’s 4.2 light-years away, meaning you’d have to travel at the speed of light in 4.2 years to get there.
The sun is about 4.5 billion years old.