Unit 2: Astronomy Note Outline

Unit 2: Earth is Space
Introduction to the Solar System
Our View:
Our view of the solar system has ______as technology and scientific knowledge has ______.
Geocentric Model:
Geocentric Model – the ancient ______believed that Earth was at the ______of the universe.
Geocentric means “Earth-centered”
The sky, or heavens, are a set of spheres ______on top of one another.
Worked well by explaining why all the ______appear to rotate around Earth once per day and why the planets move ______from the stars and from each other.
One problem is that some planets seem to move backwards (in retrograde) instead of in their usual ______motion around Earth.
Heliocentric Model:
Heliocentric Model – that the ______and all the other planets orbit the ______(which is at the center).
Heliocentric means “Sun-centered”
Johannes Kepler refined this model so that the planets moved around the Sun in ______(ovals) not circles.
The Modern Solar System:
We know our solar system is just a ______part of the universe as a whole.
Neither the ______or the ______are at the center
The Sun is off center
The Sun is a the “center” with the planets moving in ______orbits around the Sun
The planets do not emit their own ______, but instead reflect the light from the ______.
Major objects orbit the Sun
There are ______planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune)
______dwarf planets (Ceres, Pluto, Makemake, Haumea, and Eris)
Although the ______is just an average star compared to other stars, it is by far the ______object in our solar system.
In general, the ______away from the Sun, the greater the distance from one planet’s orbit to the next.
The orbit of the planets are not ______, but slightly elliptical with the Sun located at one of the foci (focal point).
IF the orbital period of a planet is known than it is possible to determine the planet’s ______from the Sun.
Astronomical Unit (AU) – how ______in the solar system are often measured in
One AU is defined as the distance from ______to the ______
1 AU equals about 150 million km (93 million miles)
The greater the object’s ______, the greater the force of attraction; in addition, the greater the ______between the objects, the smaller the force of attraction.
______keeps each planet orbiting the Sun because the star and its planets are very large objects.
The force of gravity also holds ______in orbit around planets
Formation of the Solar System:
There are ______additional key features of the solar system:
All the planets lie in nearly the same ______, or flat like disk like region
All the planets orbit in the ______direction around the Sun.
These features are ______to how the solar system formed
The most widely accepted explanation of how the solar system formed is called the ______hypothesis.
A Giant Nebula:
As ______particles of dust and gas smashed ______to create larger ones, they released kinetic energy.
As the ______collapsed, the gravity at the center increased and the cloud started to spin because of its angular ______.
As it ______further, the spinning got faster
Much of the cloud’s mass migrated to its ______but the rest of the material flattened out in an enormous ______.
This disk contained hydrogen and ______along with heavier elements and even simple organic molecules.
Formation of the Sun and Planets:
As ______pulled matter into the center of the ______, the density and ______at the center became intense.
When the pressure in the center of the disk was ______enough, nuclear ______began.
A star was born – the ______, this burning star ______the disk from collapsing further.
Meanwhile, the ______parts of the disk were ______off. Matter condensed from the cloud and small pieces of ______started to clump together.
Gravity at the center of the disk ______heavier particles (rock, metal) while ______particles remained further out in the disk.
Separation of the Planets:
Inner Planets:
Because of the ______sorting of material, the inner planets (Mercury, Venus, Earth, and Mars) formed from dense ______and metal.
Outer Planets:
The outer planet (Jupiter, Saturn, Uranus, and Neptune) condensed farther from the Sun, from ______materials as hydrogen, helium, water, ammonia, and methane.
Out this far these materials form ______particles.
Kepler’s Law of the Solar System:
Supports the nebular hypothesis and our understanding of the solar system.
The path of each planet is like an ______, the Sun at the focus (center).
Each planet revolves in an imaginary line over ______areas.
The planet must go ______when farther from the Sun and ______when closer to the Sun.
The time it takes the planet to orbit the Sun (______period) is proportional to the distance from the Sun.
Measured in ______years
Planets distance to the Sun is expressed in astronomical units (AU) – the average distance between the Earth and the Sun
Planet Earth
Earth’s Shape:
Earth is a ______, an orbital spheroid, which is a sphere that is a bit squished down at the ______and bulges a bit at the ______.
Half of the sphere is a ______.
Earth’s Magnetism:
Earth has a magnetic ______that behaves as if the planet had a gigantic bar ______inside of it.
The magnetic field arises from the ______of molten iron and nickel metal in Earth’s outer ______core.
The magnetic field shields the planet from harmful ______from the Sun.
Earth’s Motions:
Axis – an imaginary line passing through the ______of the Earth that goes through both the ______pole and ______pole.
Rotation – the Earth spins around its ______creating day/night (24 hours for 1 rotation)
Revolution – the orbit of the Earth around the ______(365 days/1 year)
Earth’s Rotation:
An observer in space will see that the Earth requires 23 hours, 56 minutes, and 4 seconds to make ______complete rotation on its axis.
Since the Earth moves around the ______at the same time that it is rotating, the planet has to turn just a little bit more to reach the same place relative to the Sun
At the equator, the Earth rotates at a speed of about 1,700km per hour, but at the poles the movement speed is nearly nothing.
Earth’s Revolution:
One ______revolution around the Sun takes 365.24 days.
Earth’s orbital path is an ______which causes the planet to sometimes be farther away from the Sun (______) than at other times. The closest the Earth is to the Sun is called ______.
Earth’s elliptical orbit has ______to do with Earth’s seasons.
Earth’s Seasons:
The reason Earth (or any other planet) has seasons is that Earth is tilted ______on its axis.

Northern Hemisphere / Southern Hemisphere
Summer (the North Pole points ______the Sun) / Winter (the South Pole points ______from the Sun)
Winter (the North Pole points ______from the Sun) / Summer (the South Pole points ______the Sun)

Earth’s Moon:
Lunar Characteristics:
The Moon is the Earth’s only natural satellite (a body that moves around a ______body in space)
The Moon orbits the Earth for the same reason the Earth orbits the Sun - ______!!!!!
Lunar – having to do with the ______
Moon’s Movements:
The Moon makes one complete ______around the Earth every 27.3 days
The Moon rotates on its ______every 27.3 days
This means the same side of the Moon always faces the Earth which is what we see in the night sky
The Moon only reflects light from the ______.
The Lunar Surface:
The ______of the Moon is very different
With no plate tectonics, features are not ______.
With no atmosphere, features are not ______.
Maria – the ______spots on the Moon mean “seas”, since this is what the ancients thought they were.
Terrae – the ______parts of the Moon, or highlands
Lunar Interior:
Like the Earth, the ______has a distinct crust, mantle, and a core
The Sun and the Earth-Moon System:
Introduction:
The ______of the Earth relative to the Sun, and the ______of the Moon and Sun relative to ______affect different phenomena on Earth including:
Day and Night
Seasons
Tides
Phases of the Moon
Day-Night Cycle:
Earth ______once on its axis every 24 hours
The Sun appears to move across the sky from ______to ______each day.
HOWEVER the Sun is ______moving, the Earth is rotating
Shadows – areas where an object ______a light source so that darkness takes on the form of that object.
Earth’s Seasons:
Caused by the ______tilt on its axis
At the ______Solstice, June 21st, Earth’s axis points ______the Sun and so the Sun is directly ______at its furthest north point of the year, the Tropic of Cancer.
During the summer, areas north of the ______experience longer days and shorter nights
The ______occurs on the Winter Solstice, December 21st
Solar Eclipse:
Occurs when the ______moon passes directly ______the Earth and Sun.
This cast a ______on the Earth and blocks Earth’s view of the Sun.
Solar Eclipses are ______and usually only last a few minutes because the Moon casts only a small shadow.
Lunar Eclipse:
Occurs when the ______moon moves through Earth’s shadow.
This only happens when Earth is between the Moon and the ______and all three are lined up in the same plane (called the ecliptic).
A total lunar eclipse occurs when the Moon travels completely in Earth’s ______(shadow).
Phases of the Moon:
The Moon does ______produce any light of its own – it only ______sunlight.
As the Moon moves around the Earth, different portions of the ______are illuminated which causes the phases of the Moon.
It takes 29.5 days for the Moon to make ______cycle relative to the Sun and go through all the phases.
The difference of 29.5 and 27.3 is that while the Moon is orbiting the Earth, the Earth is moving along its orbit so it takes longer for the Moon to reach the same position relative to the ______.
The Tides:
Tides are the ______rising and falling of Earth’s ______water in response to the gravitational attraction of the Moon and Sun.
The Moon’s ______pulls ______on Earth’s water causing it to bulge out in the direction of the Moon.
On the other side of the Earth, a high tide is produced where the Moon’s pull is the ______.
There are ______high tides and ______low tides in one tidal day.
Spring Tides:
The gravity of the Sun also pulls Earth’s water ______it and causes its own tides.
When the Sun and Moon are in ______, during the ______moon and the ______moon their high tides add up and create a ______tide.
During a spring tide, high tides are really ______and low tides are really ______.
Neap Tides:
When the Earth and Sun are in line but the the Moon is ______to the Earth a neap tide occurs.
In a neap tide the difference between high and low tides is not very ______since the pull of gravity from the Sun partially cancels out the pull of gravity form the Moon.
Types of Radiation Through Space:
Electromagnetic Radiation:
The Earth is ______from the rest of the universe by very large expanses of space.
Very rarely matter from the outside of Earth’s ______reaches us.
Example: When a meteorite makes it through the atmosphere from elsewhere in the Solar System.
HOWEVER ______can travel across ______space, and as it does, it carries both energy and ______.
Electromagnetic Radiation – energy that is ______through space as a wave (example: ______)
The Speed of Light:
Light travels ______than anything else in the universe
Example: Light from the Sun takes about ______minutes to reach the Earth.
Light-Year – a unit of ______that is defined as the distance that light travels in a year
Example: Proxima Centauri (the closest star to us after the Sun) is 4.22 light years away. This means the light takes 4.22 years to reach us.
Looking Back in Time:
Example: The Andromeda Galaxy is about ______million light years away from Earth.
When you look at this galaxy you are seeing it as it was 2.5 million years ago!
Electromagnetic Waves:
______is one type of electromagnetic radiation :
Light is ______that travels in the form of an electromagnetic wave.
______light – the light that human eyes can ______- comes in a variety of colors
The ______of visible light is determined by its wavelength
Electromagnetic Spectrum – shows the full range of electromagnetic radiation
Fun Facts:
Observing ______and motions in the sky helped ancient people keep track of time.
By understanding ______rhythms, people could know when to plant crops.
They also timed many of the religious ceremonies to coincide with events in the heavens.