Transcript ASTRONOMY After Unit 2 you should be able to

UNIT 2: ASTRONOMY
After Unit 2 you should be able to:
o Understand scaling: solar system, galaxy, universe
o Understand that we are a part of a spiral galaxy known as the Milky
Way
o Know the approximate age of the universe and solar system
o Understand the Big Bang theory and supporting evidence such as
cosmic background radiation and red-shift of light
o Understand the process of fusion taking place in the Sun
o Understand how the solar system formed, what layered the planets,
and how they were separated into two distinct groups: Jovian and
Terrestrial
o Differentiate between a comet and an asteroid
o Understand how moon phases are observed
o Understand the difference between the sidereal period and synodic
period of the moon
o Understand what impacts the formation of high and low tides
o Differentiate between lunar and solar eclipses
o Use the Electromagnetic Spectrum, Characteristics of Stars, and Solar
System Data charts in the ESRT
Unit 2 vocabulary you should be able to use and understand:
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Universe
Star
Sun
Solar system
Galaxy
Milky Way galaxy
Spiral galaxy
Singularity
Big Bang theory
Cosmic background
radiation
Radiation
Visible light
Wavelength
Electromagnetic
spectrum
Red-shift
Blue-shift
Doppler Effect
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Luminosity
Supernova
Massive
Giant star
White dwarf
Main sequence star
Fusion
Atoms
Gravity
Density
Terrestrial planet
Jovian planet
Gas giant
Period of revolution
Period of rotation
Equatorial diameter
Eccentricity
Mass
Moon
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Comet
Asteroid
Impact crater
Celestial object
Sidereal period
Synodic period
Waxing
Waning
Crescent
Gibbous
Tides
High tide
Low tide
Spring tide
Neap tide
Solar eclipse
Lunar eclipse
The universe is vast. Incredibly, incredibly vast. Even with modern
technology, humans are unable to leave even our solar system within the
timeframe of their lives. Astronomy is therefore much more abstract
and theoretical than other disciplines here on Earth.
Scaling the Universe
The true dimensions of the universe
are unknown, but it has been said (in
an expression) that there are as many
stars as grains of sand on all the
beaches of the world.
 Our solar system surrounds a star
known as the Sun
 Our solar system is a part of
many solar systems that make up
the Milky Way galaxy
Galaxies
 Galaxies take on a variety of
shapes
 The Milky Way is known as a spiral
galaxy, with our solar system
located in one of the outer arms
 There are billions of galaxies that
make up the visible universe
Age of the Universe
 Our universe is estimated to be
about 13.7 billion years old
 This estimate is based on the
projected expansion from a
singularity (single point) based on
current evidence
The Big Bang
 The Big Bang is the current
accepted theory for the
expansion of the universe
 Approximately 13.7 billion years
ago there was a rapid expansion
and differentiation of matter that
created the universe
Evidence for the Big Bang
 The Big Bang is supported by two
pieces of evidence:
 Cosmic background radiation
 Red-shift of visible light
To understand the evidence
supporting the Big Bang, you must
first understand radiation traveling
through space.
 Electromagnetic radiation travels
in waves
 Shorter wavelengths = higher
energy
 Wavelengths of radiation can be
stretched or compressed
Cosmic Background Radiation
 Radiation exists from an
explosion, believed to be from a
time period following the Big Bang
Red Shift of Visible Light
 Light from distant sources that are
moving away from an observer
experiences stretching in the
wavelength towards the red end
of the spectrum
 Light from distant galaxies is redshifted so they are moving away
 This phenomenon of wavelength
alteration is known as the Doppler
Effect
 When an object is moving towards
an observer, the waves are
compressed and it is blue-shifted
 This is evidence that this matter
was once together at a singularity
Stars
 Our Sun is a medium-sized yellow
star
 Stars are classified by luminosity,
color, and size
 Larger stars have a short lifespan
and can explode in a violent
supernova
 We see stars in the night sky that
have burned out long ago but their
light is still traveling towards us
Fusion
 The process of fusion unites
lighter elements and produces
heavier ones releasing massive
amounts of energy and light
 Hydrogen atoms fuse into helium
inside of our Sun heating Earth 93
million miles away
The Beginnings of Our Solar System
Our solar system is approximately 5
billion years old.
 The force of gravity caused
fragments of debris to begin
clumping together within a
spinning disc
 Our Sun would later begin the
process of fusion in the center of
the spinning disc
8 Planets
8 planets would form within this
spinning disc
 The densest material was closest
to the Sun
 This formed rocky, denser planets
known as the Terrestrial planets
 The less dense, gaseous, and icy
Jovian planets formed beyond the
asteroid belt
Terrestrial Planets
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Mercury
Venus
Earth
Mars
Jovian Planets
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Jupiter
Saturn
Uranus
Neptune
Other Components of Our Solar System
 Comets (primarily ice and dust)
 Asteroids (rocky and metallic)
 Impact evidence is recorded in the
geologic record (as craters) along with
mass extinctions but erosion and
deposition have erased many craters
on Earth
Additional Solar System Data
 Found in the ESRT
Our moon is critically important to life here on Earth. In addition to our
tides, the moon is responsible for maintaining Earth’s rate of rotation.
The Moon
 The Moon revolves around Earth once
every 27.3 days (sidereal period)
 Coincidentally, the moon’s period of
rotation is equal to its period of
revolution meaning that we will only
ever see one side of the moon
Moon Phases
 The Moon enters phases as it orbits
Earth based on how we view the lit
side of the moon
 The time for the moon to go through
all phases once is slightly longer (29
days --- the synodic period) than its
orbit due to Earth’s revolution around
the Sun.
Tides
 The Moon exhibits gravitational pull
on the Earth
 This pull bulges water towards the
Moon as well as on the opposite side
of the Earth (high tide)
 When the Sun, Moon, and Earth are
aligned, the tides are the highest and
the lowest on Earth (spring tides)
 The Moon has a more significant
influence on tides even though it is
smaller than the Sun because it is
closer to Earth
 Tides are about 6 hours apart (high to
low)
Eclipses
Eclipses are named for the object that is
being blocked from an Earth perspective
 Solar eclipse: Sun is blocked by the
moon
 Lunar eclipse: the Moon is blocked
from the Sun’s rays by the Earth