The Solar System
18.3 Objectives • Identify the planets of the solar system and their features • Describe the formation of the solar system • Explain eclipses and the phases of the moon
Vocabulary • Planet • Solar system • Asteroid • Nebular model • Phases • Eclipse
Objective 1: Identify planets and their features • Early astronomers have known about “stars” that didn’t move like other stars • These are the planets • Early models had the earth as the center of the universe – they were incorrect
The solar system • There are 8 planets, planets reflect light • Pluto is now considered a dwarf planet • Planets reflect light
Inner Planets • Rocky and small • A few have moons
Mercury • Small • Mercury spins slowly – 3 spins every 2 orbits • Side currently facing the sun reaches 397 C • Dark side reaches -170 C • No atmosphere, no water
Venus • Thick greenhouse cloudy atmosphere • Mostly carbon dioxide • High amounts of Sulfuric acid • 90 times atmospheric pressure of earth • Surface temperature over 425 C
Earth • Ideal for life • Large amounts of water, found in all three forms • Atmosphere moderates temperatures
Mars • We have had several robotic missions to mars • Mars has mountains larger than Mt Everest • It has ice in the polar icecaps • There are many features that suggest mars used to have flowing water • Thin, carbon dioxide atmosphere
Asteroid Belt • There is an asteroid belt separating the inner and outer planets • Thousands of small rocky pieces
Outer Planets • Jupiter, Saturn, Uranus, Neptune • Called Gas Giants • Do not have a solid surface • All have rings and moons
Jupiter • Largest planet in solar system • Larger than 1300 earths • Atmosphere is hydrogen, helium, methane, ammonia • Bands are jet streams • Red spot is a hurricane twice the size of the Earth – it has been there for hundreds of years
Saturn • Planet with most pronounced rings
Uranus and Neptune • Blue Giants • Thick gas atmospheres, mostly methane (makes them blue) • Both have lots of moons
All Planets • Orbit the sun • Have enough gravity to be spherical • Have cleared other objects from their orbital path • Pluto orbits in the Kuiper belt • So it’s not a planet
Pluto the Dwarf Planet • It was either make more planets or demote Pluto • There are currently 5 • Ceres is in the asteroid belt – between Mars and Jupiter • Eris, Makemake, and Haumea are at the edge of the solar system – like Pluto • Eris is the so-called 10th planet – it was briefly called Xena after the TV show character
Pluto, Ceres, and Eris are Dwarf Planets
Objective 2: how did the solar system form? • Most accepted explanation is the Nebular Model – it formed from a cloud of stardust • A rotating disk of stardust • Planets form from accretion – stuff slammed into each other and stuck • When the sun started glowing – lighter material was pushed out to the outer planets
Objective 3: Describe phases of the moon and eclipses • The moon orbits the earth • Sunlight reflects off of the moon • The moon appears in phases because we can only see the side that faces the sun
Phases of the moon
Eclipses • There is a difference between a solar eclipse and a lunar eclipse • They are named based on what gets blocked out • Solar eclipse blocks the sun • Lunar eclipse blocks the moon
Lunar Eclipse • The earth’s shadow crosses the moon • 3 types • Penumbral – can’t be seen by eye • Partial • Total
Total Lunar Eclipse turns moon red • The light that does reach the moon goes thru the earth’s atmosphere filtering the blue light out Without the earth’s atmosphere the moon would be black
Solar Eclipses • There are fewer than 70 total solar eclipses in a century • You must be in the right place to see a total solar eclipse – the next total solar eclipse visible in the US will be in August 2017 • They are worth the road trip!
The moon is slowly moving away from us – • If the moon’s diameter were 140 miles smaller – we would not have solar eclipses
Looking at earth during solar eclipse • You can see the corona during a solar eclipse
