highschool/Grade 9/Science/SNC1DZ/Unit_5_Astronomy_Study_Sheet.md

Unit 5: Astronomy

Suns Affect on Earth

The Aurora Borealis (Northern Lights)

• The Northern Lights are the result of collisions between gaseous particles in the Earth’s atmosphere with charged particles released from the sun’s atmosphere.
• Solar winds travelling toward Earth follow the lines of magnetic force created by Earth’s magnetic field (which is strongest near the NORTH and SOUTH poles).
• Near the poles, they come in contact with particles in Earth’s atmosphere, producing a display of light in the night sky.
• Northern Lights = Aurora Borealis.
• Southern Lights = Aurora Australis.

The Solar System

Planets

1. A planet must orbit a star
2. A planet must be big enough for its gravity to pull into a round shape
3. It must be big enough to clear most asteroids out of its path for its orbit.

• If they can’t do these things, it’s not a planet, it’s a dwarf planet.

Drawf Planets

• A celestial object that orbits the Sun and has a spherical shape but does not dominate its orbit.
• Ceres, Pluto, Haumea, Makemake, and Eris
• Pluto’s tilted orbit crosses Neptune’s orbit
• 

The Inner Planets

• Mercury, Venus, Earth & Mars.
• Small rocky planets.
• Located between the Sun and Asteroid Belt.

Planet	Orbital Period	Rotation	Atmosphere	Temperature	Number of Moons	Rings?	Unique Characteristics
Mercury	88 days	59 days	None	180 to 400oC	0	No	- No atmosphere to trap heat - Contains craters - Rarely visible in our night sky because its is so close to the sun
Venus	224.7 days	243 days, (Opposite rotation)	Carbon dioxide, nitrogen	462oC	0	No	- Brightest object in the sky after the Sun & Moon
Earth	365.26 days	24 hours	Nitrogen, Oxygen	-88 to 58oC	1	No	- Ozone filters some of the damaging radiation from the Sun - Temperatures are constant - 70% of planet’s surface is water
Mars	687 days	24.65 hours	Carbon dioxide, Nitrogen	-90 to -5oC	2	No	- Called the red planet due to its rusty soil - Very dry - Once had volcanoes, glaciers, & water

The Outer Planets

• Jupiter, Saturn, Uranus, Neptune
• Large, composed of gas.
• Atopsheres consist mainlyof the gases hydrogen and helium.

Planet	Orbital Period	Rotation	Atmosphere	Temperature	Number of Moons	Rings?	Unique Characteristics
Jupiter	11.9 years	9.85 hours	Hydrogen, Helium, methane	-148oC	63	Yes	- Largest planet (11x the diameter of the Earth) - Features are its coloured bands, the Great Red Spot & hurricanes - Orbiting rings of rocks
Saturn	29.5 years	10.65 hours	Hydrogen, Helium, Methane	-178oC	60	Yes	- Second largest, no solid core - Cloudy & windy, over 1000 separate rings
Uranus	84.1 years	17.3 hours (on its side)	Hydrogen, Helium, Methane	-216oC	27	Yes	- Winds blow up to 500km/h
Neptune	164.8 years	15.7 hours	Hydrogen, Helium, Methane	-214oC	13	Yes	- Uneven orbit, Bright blue & white clouds - Has a dark region called the Great Dark Spot, which appears to be the center of a storm

Asteroids

• They are composed of rock & metal.
• Although they orbit the Sun, they are too small to be considered planets.
• Most asteroids lie in the asteroid belt, located between Mars & Jupiter.
• A meteroid is a piece of metal or rock that is smaller than an asteroid.
• Sometimes a meteroid get pulled in by Earth's gravity. They burn up in the Earth’s atmosphere, creating a bright streak of light across the sky, know as meteor (shooting star).
• Larger meteors do not burn up completely in the atmosphere and their remains, which we call meteorites, crash to the ground.
• 

Asteroid Belt

• 700,000 to 1.7 million asteroids with a diameter of 1 km or more.
• Over 200 asteroids are known to be larger than 100 km.
• 

Comets

• Comets are large chunks of ice, dust, and rock that orbit the Sun.
• As a comet approaches the Sun, radiation and solar wind from the Sun, causes a gaseous tail to form, pointing directly away from the Sun.
• A dust tail forms in the direction from which the comet originated.
• Most comets have 2 tails;
  • gaseous tail
  • dust tail
•