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Astronomy 1

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David Barrett

on 5 May 2016

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Transcript of Astronomy 1


Today’s Activity:
Lunar Lollipops

Find a “sun” in the classroom, use your Lunar Lollipop as the moon and your head as the earth, and darken in areas of the moons (on your diagrams) to represent the phases our moon goes through.
You will have 5 minutes.
When you have finished, stay at your moon so we can name all of the phases as we look at them!

Precession – the rotation of the axis of Earth as it spins on its axis. Like a top. The period of precession is 26,000 years. This means that in the year 14,000 the axis will point toward Vega.
Nutation – nodding while Earth rotates on its axis
Motions from the Northern Hemisphere
Motions from the Northern Hemisphere
Solstice: the two times during a year when the earth is tilted directly towards or away from the sun. Giving the longest and shortest days of the year.
Earth’s Seasons
#____: Which early astronomer calculated the circumference of the earth?
#____: What is the difference between geocentric and heliocentric?
#____: Which early astronomer had a heliocentric idea of the solar system and concluded that the earth is a planet?
#____: Which early astronomer discovered three laws of planetary motion?
#____: What scientific tool was invented that aided Galileo in his discoveries?
#____: What does the geocentric model show?
#____: What does Kepler’s 1st law state?
#____: What is astronomy?
#____: What are the 2 focal points on a planet’s ellipse?
DRQ’s # ____-____
Count off 1 through 10….
You’re partners will be the same number that you called out! Find them and get settled now!
1st and 2nd Period: Groups of 3
Today’s Activity:
“Touring Our Solar System”
You will need:
2 Sheets of legal paper
1 Piece of cardboard
2 Push Pens
30cm string tied in a loop
5 Colored Pencils
Scotch Tape
In groups of 3, you will be drawing planetary ellipses (like Kepler), calculating their eccentricities, and comparing ellipses and eccentricities of Earth to other planets in our solar system.
Today’s Activity:
“Touring Our Solar System”
Kepler’s 3rd Law
A planet’s orbital period is proportional to it’s distance from the sun.
The further a planet is from the sun, the longer it’s orbital period.
Orbital period is the time it takes for a single trip around the sun.
Planetary distances measured in astronomical units.
1 AU = average distance between the Earth and Sun.
150 million km (~93 million miles)
Kepler’s 3rd Law


He came up with this idea after observing Mars. He couldn’t figure out why Mars moved as it did if Mars’s orbit was a circle. So he tried to make sense of the motion assuming Mars’s orbit was an elipse.
The angles differed by 7 degrees (this is 1/50 of a complete circle). Since the distance between the two cities were 5000 stadia apart, Eratosthesnes did his math and concluded that the Earth is 250,000 stadia in circumference. This translates to 39,400 km. It is close.
The Greeks determined Earth was round because of the shadows on lunar eclipses.
By studying shadows and eclipses, the Greeks worked out reasonable values for the sizes of the Earth and the Moon and their separation.  But they didn't know the distance to the Sun, except that it was considerably farther away than the Moon.
Materials Needed:

Purpose: To draw the phases of the moon as we see it from the Earth!
Today’s Activity:
Lunar Lollipops

Waning = Decreased amount of moon lit by sunlight
Phases of the Moon
Originated from Earth when a mars sized body impacted Earth. It threw off the moon. The impact ejected crust and mantle, not core. This is why the moon is less dense than the Earth.
Radiometric dating of the material from the maria puts the moon’s age at bout 3.2-3.8 billion years old.
Lunar eclipses of the moon is caused when the moon moves within Earth’s shadow. It occurs during full-moon phases.

Solar eclipses do not occur during every new moon phase because the moon’s orbit is inclined about 5 degrees from the plane that contains Earth and the sun. The usual number of solar eclipses is 4 per year. Sometimes there are as many as 7 eclipses.
The position of the moon/Earth orbit where the moon is farthest from Earth.
The moon’s orbit around Earth is an ellipse. The distance from moon to Earth varies about 6 percent.
The position on the orbit where Earth is farthest from the sun. Occurs July 4 each year.
Equinox: the two times during a year when the sun crosses the celestial equator and when the length of day and night are approximately equal.
Motions from the Northern Hemisphere
Describe the movements of Earth known as rotation, revolution and precession
Explain how the moon goes through phases
Explain how ellipses occur
Today’s Objectives
Today’s Activity:
“Touring Our Solar System”
Instruction sheet with Analysis and Conclusion questions are on the globe table in the back.
You and your partners MUST answer the Pre-Lab Discussion Questions BEFORE getting any lab supplies!
Remember that all 3 names should be on the lab paper and I must see 3 sets of handwriting!
Kepler’s 2nd Law
Planets move faster when they are closer to the sun and slower when they are further away.
Kepler’s 2nd Law
Kepler’s 1st Law
Kepler’s 3 Laws described the motions of the planets.
Law of Universal Gravitation
The greater the mass of an object the greater its gravitational force
The force is inversely proportional to the square of the distance between two objects
This was his first name (Galilei was his last name)
He put lenses together and created his own telescope after hearing about one a Dutch lens maker had made
Discovered four satellites or moons orbiting Jupiter
Discovered that the planets are circular disks, not points of light
Venus has phases just like the moon
The moons surface was not smooth
The sun has sunspots
Discovered three Laws of Planetary Motion
the path of each planet around the Sun is an ellipse with the sun as one focus
Each planet revolves so that an imaginary line connecting it to the sun sweeps over equal areas in equal time intervals.
Developed a very sophisticated geocentric theory. The basic thing he was trying to explain was why the planets moved so unevenly along the ecliptic.
The basis of his theory was circular orbits with epicycles. There was nothing at the center of the epicyles, so one has to think of the planets making circles around an empty point in space.
He had an idea of a motionless earth with the planets moving in complicated patterns around it.
One of these complications was what he called retrograde motion.
Mars was supposedly moving backward and in a loop
Actually, this only appears to happen because earth passes Mars in its orbit around the Sun.
Known for his star catalog.
He determined the location of almost 850 stars.
He measured the length of the year to within minutes
Determined a method for predicting times of lunar eclipses
Eratosthenes is credited for first establishing the circumference of Earth.
He did this by comparing the angles of the noonday sun in two Egyptian cities, Syrene, now Aswan, and Alexandria.
Who they were and what they did do further the study of Astronomy.
Result from sunlight reflected off the moon’s surface.
Time for moon to orbit the Earth one time is called a synodic month and lasts 29 ½ days.
Phases of the Moon
The position of the moon/Earth orbit where the moon is closest to Earth
The position on the orbit where Earth is closest to the sun. Occurs January 3 each year
The time it takes for Earth to make one complete rotation with respect to a star other than our sun. It is measured by the time required for a star to reappear at the identical position in the sky where it was observed the day before. The period is 23 hours, 56 minutes and 4 seconds. This is important to astronomers.
Sidereal Day
Motions from the Northern Hemisphere
Arctic Circle: 66.5 degrees north of the equator. Summer solstice, from the arctic circle, the sun will be above the horizon for a full 24 hours. At the north pole, they will experience 6 months of daylight.
Motions from the Northern Hemisphere
The imaginary plane that connects Earth’s orbit with the celestial sphere is called the plane of the ecliptic.
Earth’s axis of rotation is tilted about 23.5 degrees.
Because of this the Earth has a yearly cycle of seasons.
Earth’s Seasons

Revolution – the revolution around the Sun is one year.
Rotation – the result is day and night
Today’s Activity:
“Touring Our Solar System”

Near 1:
Planets orbit the Sun in an ellipse (an oval) with the Sun at one focus.
Plane of the elliptic: flat plane of Earth’s orbit in space
Kepler’s 1st Law
He was a Dane
He made observations using “pointers” not telescopes
He made observations about Mars that were very precise
His assistant was Kepler
He was a Polish scientist living in the 1400’s
He concluded that Earth is a planet
He had a heliocentric idea of the solar system
What things can we observe that show us that the Earth is constantly moving?
How does it move?
Well, it moves in lots of different ways….
Think About It…
Today’s Activity:
Lunar Lollipops

Assignment Name: “Lunar Lollipops”
Draw this on your paper:
4th Period: Groups of 3
2nd Period: Groups of 3
The Planets began as solid bids of matter began to collide and clump together (accretion)
The colliding matter formed planetesimals
Formation of the Planets
The Origin of Our Solar System
Chapter 23
#____: What are the 2 major motions of Earth? Define each.
#____: What are the 2 minor motions of Earth? Define each.
#____: What is the difference between perihelion and aphelion?
#____: What is the difference between perigee and apogee?
#____: Draw a diagram of a solar eclipse and a lunar eclipse.
#____: What causes seasons?
#____: What law keeps the planets in orbit?
#____: What causes the phases of the moon?
DRQ’s: #_____-_____
Ceres, Pluto, Makemake and Eris
Large enough that their own gravity pulls them into spheres, but small enough that their gravity isn’t strong enough to keep objects out of their orbits.
Dwarf Planets
The Outer Planets: Neptune & Uranus
Newest theory suggests that the gassy planets formed about twice as close to the sun as they are now.
They were pulled outward to their current orbits and along the way traded orbits!
The outer planet area was cold enough for ices of water, CO2, and methane to form. The outer planets (Jovian planets) grew not only from solid bits of material but also from large quantities of ices.
They became large enough to gravitationally capture the lightest gasses such as H and He.
This enabled them to grow into giants.
The Outer Planets
The inner planets formed from substances with high melting points
This was too hot for ices of water, CO2, and methane (CH4) to form.
Inner Planets
The Jovian planets are huge and have densities that average only 1.5 x the density of water. Saturn’s density is less than that of water.
It is the difference in chemical composition that accounts for the density differences.
The Planets of our Solar System
The terrestrial planets are small, and more dense. (5 x the density of water). Their rocks are mostly silicate minerals and metallic iron. They have only minor amounts of gases and ices.
The Planets of our Solar System
These ran into each other and grew larger.
As they grew larger they had enough mass to exert gravitational pull and grew larger still
Formation of the Planets
According to this theory the sun and planets formed from a rotating disk of dust and gases.
As the speed of the rotation increased, the center became more concentrated to form the Sun.
The Nebular Theory
Explain how the solar system formed
List the differences between the terrestrial and Jovian planets
Today’s Objectives
Terrestrial planets (Earth Like) – small and rocky, Mercury, Venus Earth, Mars.
Jovian Planets – huge gas giants. Jupiter, Saturn, Uranus, and Neptune
Pluto doesn’t fit into either category.
The Planets of our Solar System
waxing - building up
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