Space

People have always studied what they could see in the sky.  Ancient people studied the Earth, the Moon, the stars.  They formed their own ideas about what they could see with their own eyes.  They used this information to think about the changing of the seasons which helped them to know such things as when to plant crops and when to harvest. In the 1600s, early astronomers were able to develop simple telescopes which lead to the discovery of new information about the solar system.  Today, astronomers use computers, telescopes, and a variety of spacecraft to study outer space.

Planets!  We used to have nine, and now we have eight!  Astronomers consider a planet to be an object that orbits a star and is big enough to have enough gravity to give it a round or spherical shape.  Planets are spheres because gravity pulls their mass toward their centers which creates the round shape.  In order for a space object to be a planet, it also must have its own orbit and not cross the orbit of any other planet or large body (like an asteroid).

Name that Planet
With a classmate, do research to determine which planet the interesting information refers to.

Our planet Earth is an amazing planet because it has all the right conditions to support plant and animal life.  It has water, an appropriate temperature, and an atmosphere with elements in proportions that foster life.

Earth
The 3rd planet from the Sun

1. How is earth's name different than the other planets? If the naming of earth had followed the pattern for the other planets, what might earth's name have been?
2. In what century did we finally figure out that the earth is actually just a planet? In what century did we finally have maps of our entire planet? What aided in the mapping of earth?
3. List the layers of the earth.
4. Compare the thickness of the earth's crust under the continents to the crust under the oceans.
5. Which layers of the earth are solid and which are semi-fluid?
6. Most of the mass of the earth is in what layer? In which layer is most of the rest of the mass?
7. What element makes up the composition of most of the core of the earth?
8. Describe plate tectonics. How many major plates are there? About how many small plates are there? What phenomenon is common at the boundaries of plates?
9. What percentage of the earth's surface is covered with water? In our solar system, where else does water exist in liquid form? What role does the heat capacity of the oceans play in our climate? What other process is liquid water responsible for on earth that is unique in the solar system?
10. What is the atmosphere of the earth made up of?
11. What causes the aurora borealis?
12. What are the Van Allen radiation belts? What produces them?

Of the eight planets in our solar system, all but two (Mercury and Venus) have at least one natural satellite or moon that orbits around it. The Earth, of course, has one moon.  It’s the only moon in the solar system that man has walked on.  It is also the moon that astronomers have studied the most. 

The Moon, of course, has no light of its own. It shines because it reflects light from the Sun. As the Moon orbits the Earth, we see different portions of it lit up, and the Moon appears to change shape. These changing shapes are called the phases of the Moon. These phases take place over just the half of the Moon that faces the Earth. (Remember, we only ever really see the side of the Moon that faces the earth, and we never see the far side or dark side of the Moon.) So over the course of a month which is 29.5 days, the Moon changes from new (which means you can't see it at all) to 1st quarter (which means you see half of the part of the Moon that faces us) to full (which means you see all of that half that faces us) to last quarter (which means you see the other half of the part that faces us) and then back to new again. Get it? So in other words, when the Moon is new, it means that the Sun is shining on the dark side that we never see. When the Moon is full, the Sun is shining fully on the side that we always see. When the Moon is at 1st quarter, the Sun is shining on only half of the part of the Moon we can see.

The Sun is at the center of our solar system. It is a gigantic ball of extremely hot gases that is the source of all life on our Earth. The eight planets and their moons as well as asteroids, meteoroids, comets, and everything else in the solar system orbit around the Sun.  Our Sun is so big in comparison to planets that it contains 99% of the total mass of our solar system. The Sun is a star that has been burning for billions of years and will burn for billions of years into the future.

Stars are objects in galaxies that are composed of hot gasses.  Even though stars may look very similar when we are gazing into the night sky, there are actually many different kinds of stars that are different sizes, colors, and temperatures.   Most of the stars in our sky are actually bigger than our own Sun, but they look so small because they are very far away.

Since ancient times, people have studied the night sky and looked at the stars and have given names to the groups of stars.  Groups of stars were often named after animals or after characters in ancient mythologies.  These groups of stars that have been given imaginary stories are called constellations.

Asteroids are simply chunks of rock and metal that orbit the Sun in the same way that planets orbit. They come in all sizes and shapes. Some are as big as boulders, some are as big as mountains, and some are as big as the moons that orbit many of the planets. They can be globe-shaped or pear-shaped or have strange irregular shapes like any other big rock. Their shapes often change as they smash into each other as they orbit. The smaller bits and pieces that break off asteroids are called meteoroids.

Astronomers used to think that asteroids came from a planet that may have existed between Mars and Jupiter. They thought that perhaps this planet had exploded. This would explain why some asteroids are composed of all rock, some are all metal, and some are rock and metal mixed--the same compositions that would have made up the mantle, core, and crust of the exploded planet. Most astronomers today, however, think that asteroids are leftover material from when the solar system was formed.

A meteor is simply a piece of space rock zooming through Earth’s atmosphere.  Most of these pieces of space rock burn up in the atmosphere and never reach the Earth.  The pieces of space rock that make it through Earth’s atmosphere and hit the ground or the ocean are called meteorites. 

When a piece of space rock is orbiting the Sun, it is called a meteoroid.  If a meteoroid enters the Earth’s atmosphere (where it usually burns up), it is called a meteor.  If a meteor hits the Earth’s surface it is called a meteorite.

Comets have been called big, dirty snowballs because they are composed of rock dust wrapped around a big ball of ice. The rock dust and ice may be matter left over from the time the solar system was formed.

As a comet gets closer to the Sun, the heat of the Sun starts to melt the ice of the comet and turn it to gas. The gas and the dust are released and form a cloud that reflects sunlight (a comet has no light of its own), and the comet becomes visible. This cloud of dust surrounding the nucleus of the comet is called the coma. The nucleus and the coma together are called the head of the comet. The comet grows in size and brightness as more and more gas and dust are released from its coma. The solar winds cause the dust and gas to gather behind the comet, giving it a tail. In its long elliptical orbit, after the comet loops around the Sun, it begins its long journey back to the distant part of the solar system. It gradually appears smaller and dimmer, and it loses its tail as it cools down and freezes. Eventually, it disappears from view.

Most comets follow huge orbits in the solar system and may not return to our view in Earth's skies for thousands of years if ever. However, some comets appear at regular and more frequent intervals. They follow orbits that stay within or close to the orbits of the planets. These comets are called periodic or regular comets. The most famous one is Halley's Comet which appears every 75-76 years. It is named after the English astronomer Edmond Halley.

People have been aware of comets since ancient times. Some people believed that comets were made of poisonous gases and that if the earth passed through the tail of a comet, Earth's inhabitants would be killed. During Halley's Comet's 1910 visit, merchants even sold comet pills to protect people from the gasses.

Both the Moon and the Earth cast a shadow as the light of the Sun falls on them. A lunar eclipse occurs when the Moon passes into the Earth's shadow in space.

A solar eclipse happens when the Moon passes in front of the Sun during the day and blocks its light to the Earth. If the Moon only partly covers the Sun, it is a partial eclipse. In order to fully see a solar eclipse, you have to be in the right place at the right time. The part of the Earth where you can see the full solar eclipse is called the path of totality. The path of totality is usually only about 75-100 miles wide because the Moon is very small compared to the size of the Sun. Only people in the path of totality actually see the full eclipse; everyone else sees a partial eclipse. A total eclipse of the Sun is only visible from any given spot on Earth every 360 years.

From ancient times, eclipses have elicited feelings of fascination and fear from observers. Ancient peoples often thought that eclipses were signs from angry gods or warnings of impending doom. Eclipses ARE fascinating and often unforgettable. Today there are people who are ardent eclipse followers. They track current lunar and solar eclipses and travel to those places on the globe where the eclipses can best be observed.

Our solar system is simply everything in outer space that orbits around our Sun.

Our Milky Way galaxy is not the only galaxy in the universe.  But it is the most interesting, because WE live in it! 

On the Earth, we get warmth and light from the Sun. The tilt of the Earth as it rotates around the Sun causes us to have differing amounts of warmth from the Sun and is why we have different seasons.

The Earth does not rotate on it axis in a strait vertical manner.  The Earth is tilted on its axis at an angle of about 23.5°.  It is this tilt of the Earth on its axis as it orbits around the Sun that causes the Earth’s seasons.  When the tilt of the Earth in the Northern Hemisphere is pointing toward the Sun, it is summer.  When the tilt of the earth in the Northern Hemisphere is pointing away from the Sun, it is winter.

When the North Pole is tipped toward the Sun and the South Pole is tipped away from the Sun, it is summer in the northern hemisphere and winter in the southern hemisphere.

We live in the northern hemisphere. When the northern hemisphere of the Earth is tilted toward the Sun, Earth receives the most direct and intense solar energy. It also has more hours of daylight. This is when the northern hemisphere has its warmest season, summer