Have you ever
wondered what is really in outer space? What exactly is
the universe? The word universe is used to refer to all of outer space.
Astronomers have studied space for many years, but still have more questions
No one knows just how large our universe really is. We do know
that the universe is immense and the distances between objects are tremendous.
But how far is “far away”? Let's give a try. Imagine that the distance
between the Sun and the Earth is equal to the size of one grain of sand.
Using this size as a comparison, then the planet we call Pluto would
be 30 feet away. The closest star beyond the Sun, called Alpha Centauri,
would be 50 miles away. This makes it easier to understand just how far
away things in outer space really are.
However, astronomers prefer to use
term “light-years” to measure distances from Earth. A light-year describes
how far light can travel in one year. Astronomers chose light as a reference
point because it travels faster than anything else does. In fact, if you
shined a beam of light all the way around the world, it could go around
7 ½ times in one second. Now that is speedy traveling! Scientists
guess that the universe is at least 10 billion light-years across, and it
seems to be getting larger.
How big is our universe? Discuss the frame of reference in the story.
The universe is made up of a lot of
empty space. Huge swirling masses of stars, called galaxies, are scattered
through the universe. Each galaxy is made of billions of stars. Our solar
system can be found within a galaxy, called the Milky Way. The Milky Way
has a shape similar to a fried egg with a nice big yellow in the center.
It is a spiral galaxy. There are two other types of galaxies.
One is an elliptical galaxy, which is round and the other is an irregular
galaxy which doesn't have any real shape. Our solar system would be
located about half-way between the yoke and the edge of the egg white.
What type of galaxy is the Milky Way?
There are many different kinds of stars,
some old and some new. Some stars are brighter than others. Stars that are
hottest appear white through a telescope. Stars that are not quite as hot
appear yellow, like our Sun. Those stars that are even cooler will appear
red in color. Stars are born, grow older, and then die. They are constantly
repeating this life cycle, even though they are not really alive. Have you
ever looked for the Big Dipper or the Little Dipper in the sky at night.
If you have, then you have looked for constellation. Constellations are
patterns of stars that form a specific shape in the sky.
Why do you think some stars appear brighter than others?
What are the groups of stars in the sky that form a shape called? Name two.
In between the stars, there are cloud-like
shapes of gases and dust called nebulae. A single nebula can have almost
any shape. Some nebulae do not give off any light. We can see some of them
because they reflect light of nearby stars. A star is born when the gases
in these clouds condense enough for nuclear reactions to begin. A star is
like a nuclear bomb inside a very strong box. Instead of exploding all at
once, imagine the box opening and closing, releasing the bomb's energy a
little bit at a time, over a long period of time. That is what a star does.
A star will continue to burn up its gases and give off heat and light for
millions of years. It may end its life quietly by becoming a black dwarf
(a very small star that emits no visible light) when it can no longer shine.
Or, it may end in a supernova explosion (a very big, bright explosion).
What do you think the difference is between a black dwarf and a supernova?
In addition to planets and moons in
our solar system, there are bodies known as comets, asteroids, and meteors.
Comets are like dirty snowballs made of frozen gases, dust, and rock particles.
They travel in oblong orbits around the Sun. As they get closer to the Sun
they become warmer and begin to melt. Sometimes a gas “tail” is formed from
the melted gases. If you looked at a comet through a telescope, it would
look like a fuzzy head with a long tail. You may have heard of Halley's
Comet. This comet was named after Edmund Halley, who predicted it would
return. Maybe some day you could have a comet named after you.
Describe a comet? What did Edmund Halley discover?
Asteroids and meteors are also found
in space. These are really just pieces of space “junk”. They are made of
bits of rock and metal. Asteroids are quite large and meteors are smaller.
A meteor that enters the Earth's atmosphere at a high speed usually burns
up. This kind of meteor is called a shooting star even though it is not
really a star. It is called a meteorite if it lands on the ground.
What is the difference between a comet and a shooting star?
What is in our universe? Be specific. .
Now you know the universe is enormous.
It includes billions of galaxies, planets, moons, stars, meteors, comets,
and so much more that is yet to be discovered. Astronomers will understand
more about how stars are formed and how huge our universe really is one
day. For now, we can all observe some of the amazing characteristics of
outer space each night and leave the rest up to our imaginations and the
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