Final Review.docx

**Solar System** a. Our solar system consists of 8 planets: - Mercury - Venus - Earth - Mars - Jupiter - Saturn - Uranus - Neptune b. To be considered a planet i. Be in orbit around a **star** (like our Sun) ii. **Dominate** its orbit (i.e. its mass...

**Solar System** a. Our solar system consists of 8 planets: - Mercury - Venus - Earth - Mars - Jupiter - Saturn - Uranus - Neptune b. To be considered a planet i. Be in orbit around a **star** (like our Sun) ii. **Dominate** its orbit (i.e. its mass must be **greater** than anything else that crosses its orbit) \[Think of why pluto isn't considered a planet\] c. Our solar system has two main types of planets: iii. **Terrestrial** planets: 1. **Mercury, Venus, Earth and Mars** 2. These **smaller** planets have **hard**, **rocky** surfaces. iv. **Gas giants**: 3. **Jupiter, Saturn, Uranus, Neptune** 4. These planets are much **bigger** and are composed of **gases** and **liquids.** d. Our solar system also consists of smaller objects that orbit the Sun. Pluto is a **dwarf planet** -- it doesn't meet the new definition of a planet because it doesn't dominate its own orbit. v. Pluto's orbit crosses **Neptune's** orbit (that means that Pluto is not the largest object that crosses that path). https://www.nasa.gov/sites/default/files/thumbnails/image/edu\_what\_is\_pluto\_3.png e. **Moons** are **natural satellites** that orbit **planets** or **dwarf planets**. The planets and dwarf planets orbit the Sun, and the moons tag along for the revolution. vi. Some moons are as large as planets! **More massive** planets tend to have more moons. Jupiter is the heaviest planet and has **79** confirmed moons. f. Asteroids - Even smaller than dwarf planets and moons are the **asteroids**. Asteroids are not large enough to form a **spherical** shape under gravity, so most of them are **irregularly** shaped. Asteroids are made of **rock** and **metal**. g. **Meteoroids** are small pieces of **metal** or **rock**. Meteoroids can be as small as a piece of **dust** or as large as a car or building! vii. Meteoroids have different names depending on their **location**. If a meteoroid were to enter Earth's **atmosphere** it would be called a **meteor**. If one were to hit the **surface**, it would be called a **meteorite.** h. Beyond the gas giants is the **Kuiper belt** (rhymes with viper) which is full of **dwarf planets**, **asteroids** and **meteoroids**, **ice** and **dust.** i. The **Oort cloud** (rhymes with port) shows the boundary of our solar system. 2. **Geocentric v. Heliocentric Views of Our Solar System** j. The Geocentric Theory - The earth is located at the center of the *universe* and all the planets revolve around the earth.  viii. Aristotle (Greek philosopher) - placed the earth at the center of the universe and all of the planets, sun and stars around it. He reasoned that if the earth rotated, we should fly off into space. Since we don\'t, the earth can't be moving. ix. Ptolemy - advanced the geocentric theory in a form that prevailed for 1400 years. He added mathematics to support the theory k. Heliocentrism -- Developed by Copernicus who advanced the theory that **[the]** **[Earth and other planets revolve around the Sun]**. This was highly controversial at the time. x. Meaning that The Sun is the center of our *solar system* xi. Galileo - published his discoveries and support for the Copernican model in two books published in 1616 and 1632. 5. After his first book, *\"Starry Messenger\"*, was published he was warned by the Church not to publicly support Copernicus again. 6. Galileo supported Copernicus' theory which clashed with the religious views of the time, he underwent many trials, and was even sentenced to house arrest for his remaining years. 7. **[His view has withstood the test of time.]** 8. **[Today we talk about our Solar System, not our Earth system]** 3. **Eclipses** l. An eclipse is an **astronomical event** involving objects **casting shadows** on one another. xii. There are two main types of eclipses, **solar** eclipses and **lunar** eclipses. Solar eclipses occur when the **Moon** casts a shadow on **Earth**. 9. Solar eclipses occur when the **Moon** passes between the **Sun** and **Earth.** A close up of a clock Description automatically generated xiii. Lunar eclipses occur when the **Earth** casts a shadow on the **Moon**. 10. Lunar eclipses occur when the **Earth** is located between the **Sun** and the **Moon.**  m. Eclipses can only occur when the Sun, Earth and Moon are **aligned**. This alignment is called **syzygy** (si-zi-gee). xiv. The geometry of Sun, Earth and Moon aligning in syzygy repeats in **predictable patterns**. Every 18 years the same patterns of eclipses are seen with a predictable shift in location. n. Solar eclipses xv. A solar eclipse can only occur during a **New Moon**, because the Moon has to be in between the Earth and the Sun. 11. There are 3 types of solar eclipses: **total, partial** and **annular**. During the total solar eclipse, the Sun’s corona, only visible during the total eclipse, is shown as a crown of white flares from the surface. The red spots called Bailey\'s beads occurs where the moon grazes by the Sun and the rugged lunar limb topography allows beads of sunlight to shine through in some areas as photographed from NASA Armstrong’s Gulfstream III. Photo Credit: (NASA/Carla Thomas) Annular solar eclipse xvi. In a **total solar eclipse**, the Moon completely blocks the Sun. This is event is called **totality**. Only the Sun's **corona**, its outermost layer, is visible. xvii. A **partial solar eclipse** occurs when the Moon only blocks a **portion** of the Sun. xviii. The Moon crosses in front of the Sun off-centre. Parts of Earth experience **less sunlight** during the eclipse, but it does not get extremely dark during the day. xix. An **annular solar eclipse** occurs when the Moon is farther from Earth, and it can only block the **central portion** of the Sun. o. Lunar eclipse xx. Lunar eclipses occur when the **Moon** **passes through** **Earth's shadow** xxi. Lunar eclipses occur when the **Moon** **passes through** **Earth's shadow** xxii. Like solar eclipses, lunar eclipses can be **partial** or **total**. There are no annular lunar eclipses because Earth's shadow is much larger than the Moon's shadow xxiii. During a total lunar eclipse, the Moon appears **red**. This is sometimes called a "**blood moon**". Different cultures had their own explanations for this phenomenon, but it is quite simple to explain using the science and the geometry of the Earth's shadow. 4. **Phases of the Moon** p. As the Moon orbits the Earth, we observe the Moon forming different shapes. The Moon never changes shape of course! xxiv. What causes the moon phases (also called the moon cycle, lunar phases, or lunar cycle)? xxv. It is all based on the position of the Moon relative to the Earth (the observers) and Sun. xxvi. The Moon does not create its own light, it **reflects the Sun's light**. As the Moon orbits the Earth, one side is always facing the Sun. That side is always **illuminated**. That is not always the side that we see.  q. When the Moon is **in between** the Earth and Sun, the side of the Moon we see is **dark**. This is called a **New Moon**. The illuminated side of the Moon is facing away from Earth. r. When the Earth is in between the Moon and Sun, the side of the Moon we see is **fully illuminated**. This is called a **Full Moon**. The illuminated side of the Moon is facing towards Earth. s. The following are all the phases of the moon: File:Moon Phase Diagram for Simple English Wikipedia.GIF xxvii. The terms **waxing** and **waning** refer to whether the Moon is\ "**growing**" (waxing) or "**shrinking**" (waning). The Moon is not actually growing or shrinking, the **illuminated part** that we observe grows or shrinks throughout the Moon's orbit. t. There are two ways to measure how long it takes the Moon to orbit Earth. xxviii. **Sidereal Month** (Sid-ere-al) -- One full **revolution** around Earth. The Moon moves 360 degrees around the Earth (one circle). This takes about **27.3 days**. xxix. **Synodic Month** -- The Moon completes **all phases** (for example, from New Moon to New Moon). This takes about **29.5 days**. 12. Since the Earth is moving through space as well, the Moon has to travel a slightly **longer distance** to get back into the New Moon phase. 5. Seasonal Change u. Earth has an **axis** about which it spins. Every spin, also called **rotation**, about Earth's axis gives us **day and night**. Earth orbits around the Sun. This is called a **revolution**. One revolution takes **one year**. xxx. As the Earth revolves around the Sun throughout the year, different parts of the Earth are **tilted towards or away from** the Sun.  v. When the Northern Hemisphere is tilted **away** from the Sun it experiences **winter**. The Southern Hemisphere experiences **summer** at this time because it is tilted **towards** the Sun https://upload.wikimedia.org/wikipedia/commons/thumb/1/12/Seasons.svg/1280px-Seasons.svg.png xxxi. Areas along the equator get **12 hours of daylight** and **12 hours of night** consistently throughout the year, so this area does not experience seasons. w. North and south of the equator the length of day and night **changes** throughout the year. (Longer days in the summer, longer nights in the winter) xxxii. **Equinox** means "**equal night**". It is a day in which there are **12 hours** of day and **12 hours** of night everywhere on Earth. This occurs **twice** during the Earth's revolution: in **March** and in **September** x. A **solstice** occurs on **two days** each year. These are the two days that receives the **most** or the **least** amount of **sunlight** (depending on where you live). xxxiii. During the June solstice, the Northern Hemisphere receives the **most** sunlight of any day in the year. y. Planets without a tilted axis do not experience seasonal changes throughout their revolution around the star. Their poles would receive the **least** amount of sunlight and their equator would receive the **most** sunlight. **Mercury, Venus and Jupiter** have very little axial tilt, so they do not experience significant **seasons**. z. Uranus' axis is so **tilted** that it is almost **parallel** with its orbital path. In Uranus' 84-year orbit one pole will get **42 years** of continuous **sunlight**, followed by **42 years** of **darkness**!!