Astronomy Notes PDF

# Asteroids, Comets, Meteors - **Asteroids** - Small, rocky objects located mostly in the asteroid belt, which is located between Mars and Jupiter. - Pieces of metal or rock in the solar system that are smaller than asteroids. - **Meteoroids and Meteor** - When meteoroids are pulled into...

# Asteroids, Comets, Meteors - **Asteroids** - Small, rocky objects located mostly in the asteroid belt, which is located between Mars and Jupiter. - Pieces of metal or rock in the solar system that are smaller than asteroids. - **Meteoroids and Meteor** - When meteoroids are pulled into Earth (due to Earth's gravity) friction causes them to burn up, this causes a bright streak of light across the sky, we call this a shooting star. - When the meteoroid burns up in the atmosphere (because of friction), it is called a meteor. - If the meteoroid doesn't burn up and then hits Earth, we call it a meteorite. - **Comets** - Comets are chunks of ice, dust and rock in a very long and elliptical path around the sun. - As the comet nears the sun, the ice on the comet sublimates and turns into gas. - This gas is pushed away from the sun because solar winds and radiation pushes this gas away. We call this gas a coma. - **Planets (8.3)** - **Condition for planets** - A planet must be in orbit around a star, must have enough mass to be pulled into a stable sphere by gravity, dominate its orbit (greater mass than anything that crosses orbit). - **Dwarf Planet** - satisfies all but last condition. - **Elite Plane** - All 8 planets on a plane. # The Solar System - **The Sun** - 99.85% of the mass of the solar system. - Centre of the solar system. - Produces energy as electromagnetic radiation (light). - Emits charged particles known as solar wind. - **Inner Solar System** - **Terrestrial Planets:** Mercury, Venus, Earth, Mars. - Small, made of rock and metal. - None to few natural satellites (e.g. moons). - Cratered surfaces. - **Asteroid Belt** - Asteroids up to 950 km across. - Irregular shape, made of metal and rock. - 1 Dwarf Planet: Ceres. - **Outer Solar System** - **Gas giants:** Jupiter, Saturn, Uranus, Neptune. - Large, made primarily of gases. - Many satellites. - All have ring systems. - **Scientific Notation** - Used for big numbers. 1. Write first 1 number then rest with decimal. 2. "x" then 10. 3. Exponent as the number of digits after first 2. - **Example:** 700348 = 7.00348x10^5 unit. # The Sun (Continued) - **Surface of the Sun** - Is NOT smooth and featureless. - **Sunspots** - Cooler regions on the surface. - Appears darker. - The number of sunspots can vary (more sunspots = more solar activity). - **Solar flares** - Explosion of gases and charged particles. - Occurs near sunspots. - **Solar prominences** - Like a solar flare, but pulled back in by gravity. - **Solar Weather** - The sun goes through an 11 year cycle of activity. It is most active during solar maximum. During a solar maximum, the sun goes through more storms which create strong solar winds. - **Solar Winds** - Solar winds are the stream of ions emitted by the sun into space. These solar winds create the aurora's. Ions collide with our atmosphere creating light. Solar winds could damage electronics (e.g., satellites), knock out power grids. Increased radiation doses for people traveling in planes/ISS (International space station). # Seasons - Earth is on an axis; the tilt of this axis is why we have seasons. - As Earth revolves around the sun, Earth's axis always points in the same direction. - Therefore, depending on the location of Earth in its orbit around the sun, sometimes the northern hemisphere is tilted towards the sun or away from it. - When the northern hemisphere is tilted away from the sun, Canada gets less direct sunlight and the sun seems to travel a smaller path across the sky because we are angled on the very edge. - In the summer, it's the opposite, we get more direct sunlight and the sun travels a longer path across the sky. # Revolution: The motion of one body around another. # Rotation: The motion of spinning on an axis. # Night and Day - The part of the Earth that gets no sunlight is night. # Precession - Earth's axis is currently pointing towards a star called Polaris (North Star). - From Canada, the stars appear to circle Polaris. - However, as Earth rotates, its axis also turns. It takes 26,000 years for this to happen. # Celestial Sphere - Imaginary sphere that rotates around Earth on which all celestial objects appear to move, helpful for navigation. # Ecliptic - Apparent path taken by the Sun across the sky over the course of the year. # Ancient Astronomy - Calendars - Time - Navigation - Predict seasons - Planting crops - Predictions using astrology - Plan sacred/religious events. # Constellations - Some constellations can only be seen in the winter, others only in the summer. - During the day the sun's light is so bright that the stars are not visible (even though they're still in the sky) because of Earth's revolution. - Depending on Earth's location in its orbit, we face different parts of the sky at night. # Models of the Universe - **The Geocentric Model** - Proposed by ancient Greek philosophers, including Aristotle and Galileo. - In this model Earth is at the center of the universe. The Sun, Moon, five known planets and stars all revolve around Earth and were located in a series of concentric spheres that surrounded Earth. - Stars were located on the outermost celestial spheres that surround Earth. It was difficult to explain all the motions of the planets using this model. - **Heliocentric Model** - Proposed by Copernicus in the late 1500's. - In this model the Sun is at the center of the universe. - In 1610, Galileo used a telescope to observe the heavens and made observations that supported the heliocentric model. He observed Jupiter's moons and the phases of Venus. # The Phases of the Moon - Diagram of a New Moon with the Earth and Sun labelled. - Diagram of a Full Moon with the Earth and Sun labelled. # Parallax - Is the apparent shifting of a nearby object relative to more distant objects when viewed from two different locations. # Conversion - 1 AU = 1.5x10^11 m km ~= AU - 1 km = 1000 m # The Hertzsprung Diagram - 90% are main sequence stars. - Hydrogen fusion occurs in these stars. - Bigger star = faster hydrogen fusion = smaller lifetime. # Cosmic Microwave Background - Remnants of energy released in the Big Bang in the initial expansion. # Nucleo Synthesis - & the redshift (explains how the universe is expanding so therefore we can think back in time and theorize that it began from 1 point.) - Diagram of the Sun and direct sunlight.