All Science Content

Contents
Universe Characteristics Lesson
Star Life Cycle Lesson
Universe Game
Star Life Cycle Game
Universe Video

Vocabulary mouseover for definition

Nebula
Gas and dust forming stars
Star
Ball of gas, mainly hydrogen with fusion as energy source
Red Giant
An average or small star that swells as it begins to run out of fuel.
Super Red Giant
A giant or super giant star that swells as it begins to run out of fuel.
Supernova
Huge explosion of a super red giant star
Black hole
The place where gravitational pull is so strong that not even light can escape
Neutron Star
The remnant core of a collapsed massive star after a supernova
White Dwarf
The remnant star left after a red giant blows its outer layer of gas
Black Dwarf
A white dwarf that has run out of energy
Spectrograph
Instrument that scientists use to determine the composition of a star

LIFE CYCLE OF A STAR

Introduction

On first glance at the night sky, you may see only small twinkles and what seems to be a spray of glowing white throughout. But closer inspection reveals that these "twinkles" or stars are actually slightly different colors. We can see reddish stars, orange stars, blue stars and yellow stars. And of course, white stars. But what factors contribute to a star's color?

Stars are classified according to size, temperature and brightness. The temperature of a star relates to its color. The hottest stars are blue and white. The cooler stars are red and orange, with yellow being an average temperature. Peeking interest about star color makes many of us wonder, "Have stars always been the same color?" According to scientists, "NO!"

From Nebula to Star

It is believed that all stars have their beginning by gas and dust gathering together and forming a nebula. This gas and dust is pulled together by gravity. The gas and dust heat up causing a nuclear fusion of the gasses. The fusion causes energy release pushing matter out. The force of gravity pulls matter in. When the push of fusion equals the pull of gravity, a star is born!

Now I'm a Star

Some stars are bigger than others. They are bigger because their nebula was bigger. Bigger nebula, under the right conditions, forms a bigger star. This newborn star will go on shining for a long time- millions to billions of years.

What determines how long a star lives? The mass of the star determines how long. Giant stars use up their fuel source quickly, so they will die out first. The smaller stars take billions of years to use up their fuel.

The most abundant fuel source for any star is the element hydrogen, followed by helium. As the star ages, more hydrogen is fused into helium. When the hydrogen fuel source is used up, helium begins to fuse to carbon, and then more massive elements, such as calcium and magnesium. Scientists can tell what the composition of a star is by using a spectrograph. This can also help determine the age of the star.

Death of a Star

What happens when a star comes to the end of its life? That depends on the size of the star. Small and medium stars will swell into red giants, then blow off the outer layer of gas and become a white dwarf. When all of the energy is used up, the white dwarf will become a black dwarf. The giant and super giant stars will swell into super red giants then explode into a supernova. The next stage will be either a black hole or neutron star.