Space Exploration Unit 4 9 Science

What can we see in the Sky?

When you look up into the sky you can see stars, planets and other objects such as satellites and airplanes Universe – everything that exists including all matter and energy everywhere

Space Terms Astronomy – the study of what is beyond Earth Star Constellations – eg. The BIG DIPPER or the small dipper

When you look up on a clear night you see countless stars spread unevenly across the night sky. A long time ago sky-watches noticed that certain patterns of stars seem to suggest the shape of animals, mythical heroes or other objects. Different names were given to these shapes.

The stars in a constellation may appear close to each other but that may not be true. They may be great distances apart. Constellations have been used for thousands of years as calendars, timekeepers and direction finders both on land and sea.

Constellations

Leo

The Big Dipper

Orion the Hunter

The Solar System The solar system consists of our Sun and all the objects that travel around it. The objects are often referred to as Planets and moons. Planets and moons are non-luminous and do not omit their own light but reflects light from the Sun .Stars on the other hand are luminous and emit hugs amounts of light.

The Effects of Planetary Motion “Rotation” Like the Sun, most stars appear to rise in the East and set in the West. Earth’s Rotation (the spin of an object around its axis). One rotation of the Earth takes 24 hours.

The Earth’s axis is an imaginary line joining the North Pole and the South Pole. If this line continued out into space it would pass through the North Star so Canadians can see the North Star all year long.

Rotation ….seasons

The Effects of Planetary Motion “Revolution” The Earth also has another type of motion, revolution (the movement of one object traveling around another). It takes Earth one year to travel around the Sun. This motion allows us to see different starts during different seasons.

Motion of the Planets In Ancient times without light pollution the night sky was clearer. They noticed that the constellations moved together. It was noticed that five particularly bright objects moved differently. They called these objects the “wandering stars” or Planets from the Greek word that means wonderers. These planets moved through many animal shaped constellations or zodiac constellations (Greek for animal sign) What is your sign?

The Solar System

Our Solar System Each planet In the solar system is unique. The planets differ in their size, motion and temperature, in the substances they are made of, and in their degree of gravitational pull. At the center of our solar system is a star that is essential to our life on Earth- the Sun. The planets revolve around the Sun in elliptical orbits. The time it takes of one planet to orbit the Sun is called its orbital period.

Our Solar System Earth’s orbital period is about 365 days. Surface temperature varies from planets to planets and also for day to night. The planets have different densities and are made up of different combinations of chemical elements. There are four common elements that we do see in most planets: hydrogen, helium, carbon and oxygen.

Gravitational pull varies form planet to planet Gravitational pull varies form planet to planet. If you jump up and down on different planets, you would be pulled down with different forces: sometimes more than Earth, sometimes less. Astronomical unit – a distance measurement used by astronomers 1 a.u. equals the average distance form the Sun to the Earth

Space Probes As we explore the solar system we want to get as much information about the Planets as possible. We gather this information by sending probes to investigate these heavenly bodies. A space probe is an unpiloted spacecraft sent to explore parts of the solar system. The probes collect information and send it back to Earth.

Probe Name Year of Launch Scheduled Arrival Details Magellan 1989 1995 Successfully maps Venus using radar waves. Was deliberately crashed into the planet in 1995 Galileo Explored Jupiter and its moons Mars Global Surveyor/ Pathfinder 1996 1997 Two probes, an orbiter and a lander, sent to study Mars Cassini 2004 US-European probe studying Saturn and its largest moo, Titan; expected to operate until 2008 Mars Surveyor’98 1998-1999 1999 Studies the evolution of the climate on Mars and search for water in its soil

Planets Planets can be grouped into two main categories, those that are nearest to the Sun and those that are much further from the Sun.

The Inner Planets The inner planets are the four planets closest to the Sun: Mercury, Venus, Earth and Mars. They are all small and resemble Earth so they are called Terrestrial Planets.

The Outer Planets The outer planets are the four planets farthest from the Sun: Jupiter, Saturn, Uranus, and Neptune. Their atmosphere consists mainly of gases hydrogen and helium which have low densities. For this reason these four planets are called gas giants Pluto ????

Other Objects in the Solar System Planetary Moons Large natural objects that revolve around planets are called satellites or moons. Earth’s moon has a diameter of about ¼ of Earth. Studying the moons of planets helps to understand the origin of the solar system. See Bill Nye’s Activity

Asteroids In between Mars and Jupiter there is a space called the asteroid belt. It is made up of thousands of small rocky objects called asteroids. Some scientists believe that all these asteroids would have formed into a planet if the gravitational pull of Jupiter wasn’t so strong.

Meteors and Meteorites A meteoroid is a lump of rock or metal that is trapped be Earth’s gravity and pulled down through Earth atmosphere. The friction of it decent causes it to become hot and vaporize and the air to glow. This produces a bright streak of light across the sky called a meteor. Meteorites are object s that hit the ground before it is completely vaporized and will create a crater.

Comets A comet is a chunk of frozen matter that travels in a very long orbit around the Sun. Comets can have tails that are millions of km long. As the comet approaches the Sun the chuck is warmed and produces gases that are pushed outward be a solar wind and create the tail Many comets have regular period of revolution around the Sun which allows us to predict when we will see them. For example “Halley’s” comet that visits every 76 years. Its last sighting was in 1986

Halley’s Comet