This is a picture of the Eagle Nebula. The orange is gas. It would take light nearly an year to travel from the bottom to the top. This was taken by the Hubble Telescope in 1995.

The Universe probably began with a thing called the "Big Bang." Here the Universe was the size of a molecule. It suddenly started to expand. Even now the universe is still expanding. Along the way stars were formed. One of these stars was formed on the edge of the Milky Way. It had nine planets. On one, third farthest from it, life could be found. We call this planet Earth.

The Universe is made up of galaxies. In the Universe there are 2,000,000,000,000,000,000 stars. These stars make up galaxies. Each galaxy has a billion or more stars.

These stars are made up of 2 elements. Hydrogen and helium. These are two different kinds of gasses.

Why do stars twinkle? Starlight comes to us in different layers of air that move.

Stars are arranged in five different categories depending on size.

Supergiants- these are the biggest stars in the Universe.

Giants- these are a bit smaller but have a diameter that is 10-100 times that of the Sun.

Medium Sized Stars- these are a little bit bigger than the Sun.

White Dwarfs- these are small stars. When the Sun starts to expand and then shrink, it will be a white dwarf.

Neutron Stars-these are the smallest stars. They usually have a diameter of about 10 miles.

The temperature inside these stars can vary from 5,000 degrees Fahrenheit to 55,000 degrees.

Whenever we look up at the night sky at, let's say 7:00 and then later at10:00, we notice that the stars have moved from their original position. This is from the Earth rotating. The stars themselves move very little.

How do stars form? They start as gas and dust. Gradually over millions of years these clouds of gas and dust are pulled into a ball by the force of gravity. The pressure of the gas increases, and when the core gets extremely hot, nuclear reaction begins. The hydrogen becomes helium and the star begins to shine. A new star is born.

How do stars die? After shining, changes begin to occur. The star will start to expand and then pull together and shine brighter than ever before. If the star is big enough it could become a black hole!

So how will the Universe end? Will it go on forever? Not even astronomers know the answer to this question. If the Universe came to an end, it would start to shrink and become the size of that molecule we talked about earlier. Then who knows what. It could disappear or it could start expanding again.

Still, even if the Universe started to shrink it would not happen for billions, trillions, quadrillions of years. So you don't need to worry. But you know the age-old adage. Better be safe than sorry!

 

FUN FACT:

You can tell a star's temperature by its color!