The Stars and the Solar System What do you know about the solar system?

Georgia Performance Standards S4E1: Students will compare and contrast the physical attributes of stars, star patterns, and planets. Recognize the physical attributes of stars in the night sky such as number, size, color, and patterns. Compare the similarities and differences of planets to the stars in appearance, position, and number in the night sky. Explain why the pattern of stars in a constellation stays the same, but a planet can be seen in different locations at different times. Identify how technology is used to observe distant objects in the sky.

Essential Questions What is a star? How are stars alike and different from each other? How does the sun compare to other stars in the night sky? How are constellations alike and different? Why are some constellations observed during some seasons, but not during other seasons? How can technology be used to observe distant objects in the sky?

STARS A star is a huge ball of hot gases. When seen from the Earth, most stars appear as small points of light because they are very far away. They form fixed patterns that change position in the sky as Earth rotates and revolves.

A star as seen from Earth.

Star A STAR is a ball of hot gases that gives off light and other forms of energy. Stars have different sizes. White dwarf stars are about the size of Earth. Supergiant stars can be wider than 300 million miles. That is more than one thousand times the distance from Earth to the Moon.

Dwarf star Supergiant Star

How many stars are there? On the clearest night, you can see hundreds of stars. The universe holds many, many more stars than you can see from Earth. These stars are too far away to be seen with the unaided eye.

The Sun The SUN is a star. It is the largest object in the solar system. More than 1 million Earth’s would fit inside the sun. The sun is a medium sized star. It looks much larger than the stars you see at night because it is so much closer to the Earth.

Sun

Sun Living things on Earth depend on the Sun for heat and light. The Sun also emits energy in forms that would harm life. Fortunately, gases in the Earth’s atmosphere protect the surface from much of this energy.

Constellations A constellation is a group of stars that forms a pattern shaped like an animal, person, or object. Scientist recognize 88 constellations.

Constellations seen in the night sky

Great Bear Constellation The Big Dipper

Stars are always present, even during the day. You just cannot see them during the day because the sky is so bright. Each night the stars appear to move across the sky. This is caused by the rotation of the Earth.

Constellations As Earth rotates on its axis, the stars appear to rotate in the sky. Thus, the constellations change position in the night sky during the night. Different constellations become visible with the different seasons but the shape of the constellations DO NOT change.

Why do the stars in constellations stay in fixed patterns? Stars are trillions of kilometers away, far outside the solar system. Even as the Earth moves through its orbit around the Sun, each star remains nearly the same distance away.

Seasonal Constellations Some constellations can only be seen on a summer night. Others can only be seen on a winter night. This is because the Earth revolves around the sun. As it does, the part of the night sky that is visible from any one place changes.

How were constellations used long ago? People depended on the constellations in many ways. Sailors studied them to find their way at night. Farmer’s used them to mark the seasons and signal when to plant or harvest their crops.

Northern Hemisphere Summer constellations Winter Constellations

Solar System The Solar System is made up of the Sun, orbiting planets, their moons, and other objects traveling around the Sun. The Sun is the nearest star to the Earth.

Planet A PLANET is a large body or rock or gas in space that moves around a star. A planet DOES NOT produce light of its own. That is why planets almost never twinkle, while stars do twinkle. You can see planets in the night sky because of the Sun’s light reflecting, or bouncing off, of them.

Solar System Earth is one of the eight planets that orbit the sun. (Pluto is now called a dwarf planet.)

MOON You can also see Earth’s moon in the night sky. A MOON is a small, rounded body in orbit around a planet. A moon does not produce its own light. It reflects light from the sun. Most planets have at least one moon.

Moon as seen from Earth.

Earth’s Year The farther a planet is from the Sun, the longer it takes to orbit. The time it takes to complete one trip around the Sun is called a YEAR. Earth’s year is about 365 days long. Mercury makes a complete orbit in just 88 days. Neptune takes about 165 Earth years to complete its orbit around the Sun.

Sun, Moon, and Sky For thousands of years, people have been observing the Sun, the Moon, and other objects in the sky. Scientists did not learn how these objects move until a few hundred years ago. Why do you think they took so long?

TELESCOPES A TELESCOPE is a tool that makes distant objects appear larger, brighter, and sharper. Telescopes help scientists study stars, the Moon, and the planets. Scientists have used telescopes to discover that stars have regular patterns and planets move among the stars.

Never Look at the Sun NEVER look straight at the Sun, especially with a telescope. Doing so can DAMAGE your eyes. It is SAFE to look at other stars, which are more distant.

OPTICAL TELESCOPE This telescope magnifies (or makes an object appear larger) by collecting light.

Hubble Space Telescope OPTICAL TELESCOPE Hubble Space Telescope

Hubble Space Telescope It is different from other telescopes because it is in space. It moves around the Earth every 97 minutes. It was launched into space in 1990. It is the size of a school bus. It takes photographs of space from beyond Earth’s atmosphere.

RADIO TELESCOPE This type of telescope collects radio waves instead of light. Computers use the radio waves to make pictures of space. As more powerful telescopes are invented, scientists learn more about objects in space.

RADIO TELESCOPE

Essential Questions What is a star? How are stars alike and different from each other? How does the Sun compare to other stars in the night sky? How are constellations alike and different? Why are some constellations observed during some seasons, but not during other seasons? How can technology be used to observe distant objects in the sky?