Intro to Astronomy Grade 9 Science

Astronomy Intro Grade 9 Science The universe is everything that exists, including all matter and energy everywhere. The study of what is beyond Earth is called astronomy.

Astronomy Intro Grade 9 Science History… Geocentric Model The geocentric model (earth centered model) was based on an ideas from Aristotle, but refined and finished by Claudius Ptolemy. Ptolemy imagined that the solar system was made of perfect circles, but his model also had to explain retrograde motion. He did this by adding smaller perfect circles (epicycles) on the orbital paths of each planet (except for the sun).

Astronomy Intro Grade 9 Science Heliocentric Model Nicholas Copernicus with the help of Galileo proposed a model where the sun is the center of solar system. This model was not well received, but it did explain the retrograde motion better then Ptolemy’s model. Johannes Kepler added to Copernicus’s by changing the orbital paths to elliptical instead of circular. This explained the speed changes they observed in the night sky.

Astronomy Intro Grade 9 Science Origins of the Universe There are a lot of models and ideas that exist to explain how the universe came about. The current accepted scientific model is called the Big Bang theory. Which states that the universe started from an infinitesimal point that exploded in a huge release of energy and matter 10 to 15 billion years ago. The study of the origin and changes of the universe is called cosmology.

Astronomy Intro Grade 9 Science Planets orbit the sun in elliptical orbits which are caused by gravitational forces. Orbital Period is the time it takes for one full orbit. Orbital period increases as the body gets closer to the sun. Along with orbiting, a planet also rotates about a central axis.

Astronomy Intro Grade 9 Science Planets have two types of motion: Rotation Revolution Effect of Earth’s Rotation Rotation – the spinning of an object around its axis (an imaginary straight line joining the North Pole to the South Pole) The Earth’s rotation around its axis takes 24 hours. The rotation causes day and night.

Astronomy Intro Grade 9 Science Effect of Earth’s Revolution Revolution – the movement of one object travelling around another. It takes the Earth one year (365 days) to revolve around the Sun. This allows us to see different stars in different seasons. The angle of the Earth’s axis in combination with its revolution cause our seasons.

Astronomy Intro Grade 9 Science Seasons Although the Earth’s distance from the Sun changes slightly as it orbits, the distance is not great enough to cause a substantial change in the climate. The tilt of the Earth (23.5o) is what causes the seasons to change. During the summer, the Northern Hemisphere is titled towards the Sun, while during the winter the Northern Hemisphere is titled away from the Sun.

Astronomy Intro Grade 9 Science Each planet is unique in our solar system. Some of the differences are: Surface temperature Density Combination of chemical elements Gravitational field strength

Astronomy Intro Grade 9 Science The Inner Planets (Terrestrial Planets) 1. Mercury 2. Venus 3. Earth 4. Mars The Outer Planets (Gas Giants) 1. Jupiter 2. Saturn 3. Uranus 4. Neptune 5. Pluto (Dwarf Planet)

Mercury Diameter:4,878km Mass:0.0553EM Density:5.43 Gravity:0.284EG Average Temperature: 400 to -170°C

Venus Diameter:12,102km Mass:0.8149EM Density:5.25 Gravity:0.878EG Average Temperature:500°C

Earth Diameter:12,756km Mass:5.9741024 kg Density:5.52 Gravity:9.8m/sec2 Average Temperature:15°C

Mars Diameter:6,786km Mass:0.1074EM Density:3.95 Gravity:0.379EG Average Temperature: -60°C

Jupiter Diameter:142,984km Mass:317.938EM Density:1.33 Gravity:2.4EG Average Temperature: -140°C

Saturn Diameter:120,536km Mass:95.181EM Density:0.69 Gravity:0.923EG Average Temperature: -175°C

Uranus Diameter:51,118km Mass:14.531EM Density:1.29 Gravity:0.793EG Average Temperature: -214°C

Neptune Diameter:49,528km Mass:17,135EM Density:1.64 Gravity:1.122EG Average Temperature:-214°C

Astronomy Intro Grade 9 Science Solar System At the centre of our solar system is a star, the Sun, that is essential to life on Earth. The sun is the largest body in our solar system.

Astronomy Intro Grade 9 Science