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Astronomy Facts

Observer For thousands of years humans have been looking up at the sky, before we even knew the word "astronomy." Astronomy is the study of everything that is or was in space beyond the Earth's atmosphere. We are still looking up because the sky is such a fascinating place and because we are learning more and more about it everyday. Let's stretch our imaginations as we explore the world of space.


Long ago people thought that the sun, and all the other planets, revolved around Earth. A man named Galileo proved in the 1600's that the Earth and the other planets revolved around the sun. He used a special tool called a telescope to look at the sky. Visit the TIME LINE of important events in astronomical history to learn more.

Solar system

Here's more about Galileo's tool, the telescope, and the development of the many different kinds of telescopes.

Learn about Arecibo, the largest single-dish radio telescope in the world.

The Universe


How big is it?

clockWhen you look up at the night sky you are looking at the universe. Everything is inside the universe, even us, and it is impossible to imagine how big the universe is. Special astronomers called cosmologists are trying to measure it. They analyze the light from a star with an instrument called a spectroscope. By studying the spectrum they can tell whether an object is moving away from Earth or toward Earth. Based on the information from this instrument, scientists have learned that the universe is still growing outward in all directions.

How old is it?

Scientists believe that over 15 billion years ago, a powerful explosion called the Big Bang set the universe into a motion which continues today. Scientists are not yet sure if the motion will stop, change direction, or keep going forever.


How do you measure distances in the universe?

Since distances are so huge in the universe astronomers need a measurement with a big scale. They use a unit of length called a light year which is the distance light can travel in one year. Light travels very fast, so in a year it can go 6,000,000,000,000 (6 trillion) miles, or 9,500,000,000,000 kilometers.


Galaxies are collections of billions of stars, gas, and dust held together by gravity. All stars belong to a galaxy and galaxies are huge. Our sun, Earth, and all the stars you see when you look at the night sky belong to the Milky Way Galaxy. Scientists estimate that there may be 10 billion stars in our galaxy and 50 billion galaxies in the universe. Galaxies are classified by their shape: spiral, elliptical or irregular. The Milky Way is spiral.



You, too, can Classify Galaxies if you dare...


What does a quasar have to do with a galaxy?



Sun FACT: The prefix "astro" means "star" in the Greek language. Stars are large balls of gas that give off light. Scientists know that you can see about 3,000 stars with your naked eye. With powerful telescopes, scientists can see billions and billions of other stars.

How old is a star?

SunDid you know that stars vary in their size, color, and brightness? A star can be red, orange, yellow, white, or blue. Its color depends on its surface temperature, which is determined by its age and mass. Stars go through many stages in their lifetime. Some of the names for these stages are Nebula, Red Giant, Supernova, White Dwarf, Neutron Star and even Black Holes. Stars can shine for up to 10 billion years!

The Life Cycle of a star the size of the sun


The Life Cycle of a star heavier than the sun


Famous Star Stats


Our Solar System

Solar system modelThe Roman word for the sun was "Sol" so our solar system has something to do with the sun. The sun is the center of the solar system which includes eight planets, a number of planetoids, more than one hundred seventy moons, some comets, lots of asteroids, and other space objects that travel in paths around the sun. The sun is the biggest object in our solar system, yet it is a medium-sized star, and it will use up its energy and die in about 5 billion years! The sun is the reason why there is life on earth. It provides the light and heat energy that living things need to survive.

Did you know that the solar system is about 4.6 billion years old?

Did you know that if an object orbits the sun it is called a planet but if it orbits something instead of the sun it is called a moon?

Do you believe that there are over 30,000 asteroids?

There are so many interesting facts about the solar system that you'll have to go behind the scenes at these links:

Planet Facts
Solar System Facts Pluto is one of five dwarf planets! Comets Astronomy for Kids
The Earth's Moon Your age & weight on different planets Asteroids NASA's Planet Photojournal
The Earth Journey to the edge: The Kuiper Belt and the Oort Cloud. Meteoroids Amazing Sun Facts

Are Constellations real?

SagittariusThe constellations are pictures of things that people have imagined in the stars for thousands of years. They created stories about how these pictures, or constellations, were created. Many of the constellations in the northern sky were found and named by the Greeks during the Greek Empire (about 50 BC to 480 AD). Other humans, besides the Greeks, developed their own stories. Learn more about these stories and the constellations they represent at Windows to the Universe, and Mayan Astronomy.

Barbara Morgan is Idaho’s authority on space travel. Learn more about Barbara, Idaho’s first teacher/astronaut. Click here.

Kids Science Challenge


Kids' Science Challenge has a challenge this year asking kids to design a machine to help play sports on Mars. Check it out.

There’s a Dog in the Sky!
by Cherry Carl

There’s a dog in the sky
And I know why.
He’s belongs to the hunter,
And so does the horse, of course!
Maybe they’re hunting for the great big bear,
Or perhaps the dragon in its lair.
What do you see when you look in the sky?
There’s a lot to see if you really try!

This poem was written especially for Dialogue4Kids - courtesy of Cherry Carl. For additional poems on science, history, language, and holidays visit her website at: Carl's Corner

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