Seasons Thanks to the Earth’s Tilt
* Only due to the earth’s tilt
* Arctic and Antarctic are most affected
* Earth’s tilt DOES NOT change (due to the
moon!!)
* The area of the earth exposed to sun changes
Cause
* Earth’s revolution(around sun) = 365.25
days
* Earth’s Rotation (on its axis) = 24 hours
* Earth’s tilt = 23.3 0
* Seasons are NOT related to distance
from the Sun
* Earth is closest to the sun on January 3
Summer Solstice
* Northern hemisphere is tilted towards
the sun
- direct sunlight hits the Tropic of
Cancer (north of equator)
- first day of summer
* Southern hemisphere is tilted away from
the sun
Winter Solstice
* Southern hemisphere is tilted towards the
sun
- direct sunlight hits the Tropic of
Capricorn (south of equator)
- first day of winter
* Northern hemisphere is tilted away from the sun
Equinox
* neither hemisphere is tilted toward the
sun
- direct sunlight on the Equator
* Vernal Equinox – first day of spring in
northern hemisphere
* Autumnal Equinox – first day of fall in
northern hemisphere
Assignment
* Make a poster that shows the position of the Earth relative tot he sun on the summer solstice, vernal equinox, winter solstice and autumnal equinox. Include the tilt of the Earth, the Tropics, the equator and where the sun’s rays are hitting directly
Moon Phases
Moon does not rotate
Shaded side is ALWAYS shaded and light side is ALWAYS light
Moon Phases
* apparent change in the moon’s appearance throughout the month.
* half of the moon is always illuminated
* phases due tot he amount of illuminated surface seen from Earth.
* 28 day cycle
* BLUE MOON – Full moon twice in one month
New Moon
* First phase
* none of the illuminated portions in visible from the earth.
Waxing
* Illuminated portion seen form Earth gets larger.
- waxing crescent
- first quarter
- waxing gibbous
* Illuminated part gets LARGER
Full Moon
* entire illuminated side visible from Earth
Waning
* waning gibbous
* third quarter
* waning crescent
* Illuminated part gets SMALLER
Solar Eclipse
* Moon blocks sun’s rays from reaching Earth
- umbra – completely dark
- penumbra – somewhat dark
Lunar Eclipse
* Earth blocks sun’s rays from reaching the moon.
- umbra – completely dark
- penumbra – moderately dark
Assignment: Moon phase Activity in Packet
Historical Perspective of our solar system
From 1500- present day
Universe
* Early astronomers referred to our solar system as ‘the universe’
* Today we refer to all the material out ‘there’ as the universe
- there are countless galaxies in the universe
Geocentric model
* accepted explanation in the early 1500s
* Early Earth at the center of the universe and solar system.
- stars, sun, moon and other planets revolved around Earth.
* Only planets were Mercury, Venus, Mars, Jupiter, and Saturn.
Heliocentric Model
* Sun at the center of the solar system and the universe
* Everything including the Earth revolves around the Sun
* Explanation first proposed in 1543
Elliptical Orbits
* Planets orbit in eclipses
- sun at one end and is the focus
* No epicycles needed to explain planetary motion
Modern View
* planets in the solar system (Pluto may not be a planet but an asteroid
from the asteroid belt in our solar system).
* All revolve around the sun
* sun = 99.86% of solar system mass
Formation of a Solar System
Formed from a cloud of dust and gas through a series of ‘steps’
Formed about 4.6 billion years ago
Cloud of dust and gas
* 5 billion years ago there was a cloud of dust and gas
* It was rotating and contracting due to gravity
* It flattened into a disc with a flat center – one geometric plane
A star is born
Temperaturein the core of the cloud increased
* Nuclear fusion began
H + H -- > He + ENERGY
Planets formed
* Pieces of dust, gas, ice stuck together
- the masses became larger and larger
- eventually the planets formed
Inner Planet Characteristics
* inside of the asteroid belt
* terrestrial and rocky
* relatively small
* thin atmospheres
* few to no moons
* no rings
* Mercury, Venus, Earth, Mars
Outer Planet Characteristics
* jovian/gaseous
* relatively large
* thick atmosphere
* many moons
* many rings
* outside asteroid belt
* Jupiter, Saturn, Uranus, Neptune
Asteroid Belt
* Between Mars and Jupiter
* Should be a planet
- Jupiter’s gravity was too large
- Tug of war between Jupiter and the sun kept planet from forming.
Stars, Constellations, and Galaxies
What we can see.
A star is a big sphere of burning gas
The sun is our closest star.
Stars
* Most of the visible mass in the universe is stars.
* Distance affects brightness
* Burning Temperature affects color and brightness
H-R Diagram
* compares brightness, temperature and color
Magnitude
* Absolute magnitude is how bright a star actually is
* apparent Magnitude – how bright a star seems from the Earth.
Parallax
* Mathematical method used to determine distances to far away objects
Constellations
* group of stars – look like an animal or mythological figure
* Not necessarily close together – usually very far apart
Assignment:
1. Using your notes construct Uncle Al’s Sky Wheel in your workbook
2. Created your own constellation by punching holes CAREFULLY in paper. You may use only 8-12 ‘stars’ and must also include a mythological story that explains how the constellation came to be.
Star Formation
Evolution of high and low mass stars
Before a star is ‘born’
* a Nebula is a cloud of gas and dust
* Over time gravity pulls the cloud particles together forming a PROTOSTAR
* Temperature in the core increases until fusion begins. Atoms bind together -
Main Sequence
* The longest most stable period of a star’s existence
* Hydrogen fusion (binding of different elements to form something new) is occurring
- high mass star burn blue
- low mass stars burn yellow
* Our star is a low mass star
Death of a Low Mass Star
- Most of the fuel gone, the star cools, the inner core contracts and
the outer core expands forming a red giant.
*All fuel gone, it loses the outer core leaving a glowing core called a white dwarf.
* Completely cool. A black dwarf is formed.
Death of a High Mass Star
* Most of the fuel is gone, the star cools, the inner core contracts and
the outer core expands forming a red giant.
* Fusion of heavier elements occurs because more massive.
* Fuel is gone. It is very unstable and the outer core explodes in a supernova destroying everything in its path.
* after the super nova, the mass determines its fate.
- Massive; the remaining core is called a neutron star.
- VERY massive, inner core collapses into a black hole.
Concept Mapping
Using the Evolution of Stars diagram create a concept map a
star’s lifecycle
Taking it Further
1. Why can a yellow star become a black hole?
There is not enough mass and density in the star for forma black hole
2. Where does the gas and dust that forms a nebula come from?
The gas and dust come from a supernova
Hertz spring-Russell Diagram
H-R Diagram
Plots temperature and absolute magnitude (brightness) of a star
Magnitude
* Absolute Magnitude refers to how bright the star actually is
* Apparent Magnitude refers to how bright the star seems from earth
Hertzspring-Russell Diagram
* A graph of the surface temperature of a star versus its absolute
magnitude
* Compares a star’s brightness (luminosity) and temperature
* Compares a star’s color and temperature
* Temperature is highest on the left
* Brightness increases moving UP the y-axis
* Hottest stars are blue and coolest stars are red
Main Sequence Stars
80-90% of all stars fall into the middle area
Assignment
Using the H-R Diagram
1. Which is the hottest star shown? Regel
2. Which is the coldest star shown?Betelgeuse
3. What is the temperature of our sun?6000 o K
4. What is out sun’s absolute magnitude?+5
Taking it Further
How can a cool star be brighter than a hot star?
The large star has more surface area and will give off more light and shine brighter
Light Year – the DISTANCE light travels in one EARTH year
- exactly 9,460,730,472,580.8 km
- 5,878,630,000,000 miles
(about 6 trillion miles)
- about 63,241.1 astronomical units
An astronomical unit (AU, au,) is a unit of about 93 million miles). It is defined by the mean distance between the Earth and the Sun.