Chapter 22Chapter 22

Origin of Modern Astronomy Origin of Modern Astronomy

Early AstronomyEarly Astronomy

Earth is just one of eight major planets Earth is just one of eight major planets and 3 dwarf planets that orbit our sun. and 3 dwarf planets that orbit our sun.

Our sun is just one of perhaps 100 Our sun is just one of perhaps 100 billion stars that make up our galaxy billion stars that make up our galaxy the Milky Way. the Milky Way.

The Milky Way is just one of billions of The Milky Way is just one of billions of galaxies.galaxies.

Where does this knowledge come Where does this knowledge come from??????????from??????????

Ancient Greeks Ancient Greeks

___________ is the science that studies ___________ is the science that studies the universe. Astronomy deals with the universe. Astronomy deals with the properties of objects in space the properties of objects in space and the laws under which the and the laws under which the universe operates.universe operates.

““Golden Age” of early astronomy Golden Age” of early astronomy (600 B.C. – A.D. 150) was centered in (600 B.C. – A.D. 150) was centered in ___________.___________.

Greeks developedGreeks developed

The basics of ___________ and ___________The basics of ___________ and ___________ Measured the distances of the sun and moonMeasured the distances of the sun and moon Aristotle determined that the Earth was round Aristotle determined that the Earth was round

because it cast a round shadow on the moon. because it cast a round shadow on the moon. This theory was later abandoned.This theory was later abandoned.

___________ first to calculate the ___________ first to calculate the circumference of the Earth….. circumference of the Earth…..

Describe his experiment and figure his Describe his experiment and figure his mistakes.mistakes.

Here is how he did it……….Here is how he did it……….

7.20

7.20

Then he calculatedThen he calculatedHow much of How much of

a circle is a circle is ______________________??

______________________ The The total distance total distance

was?was?

39,400 km.39,400 km.

The actual The actual distance is distance is closer to closer to

40,075 km.40,075 km.

Problems with the Problems with the solution……solution……

1.1.

2.2.

3.3.

4.4.

___________ developed star ___________ developed star catalogue. He determined catalogue. He determined the locations of 850 stars, the locations of 850 stars, which de divided into six which de divided into six groups according to their groups according to their brightness. brightness.

He measured the length of He measured the length of the year to within minutesthe year to within minutes

He developed a method of He developed a method of predicting the times of predicting the times of lunar eclipses to within a lunar eclipses to within a few hours. few hours.

___________ Model ___________ Model

___________ centered solar system… ___________ centered solar system… outside the solar system the stars outside the solar system the stars traveled within a hollow sphere traveled within a hollow sphere called the celestial sphere. called the celestial sphere.

___________ Model ___________ Model

___________ centered___________ centered Aristarchus (312 – 230 B.C.) first to Aristarchus (312 – 230 B.C.) first to

believe in this model. believe in this model. This model was later proposed by This model was later proposed by

Copernicus (1473 – 1543) and proved Copernicus (1473 – 1543) and proved by his student Galileo.by his student Galileo.

This model was not accepted This model was not accepted originally.originally.

Ptolemaic System Ptolemaic System

An attempt to An attempt to explain planetary explain planetary movement referred movement referred to as ___________to as ___________..

Retrograde motion Retrograde motion is the ___________ of is the ___________ of a planet. a planet.

How is this possible?How is this possible?

______________________ : :

Concluded that Concluded that Earth was a Earth was a planet. planet.

He proposed a He proposed a heliocentric heliocentric solar system solar system model.model.

v v

Built an observatory near Built an observatory near Copenhagen. Copenhagen.

He developed and used He developed and used several instruments made several instruments made of stone to make of stone to make calculations. calculations.

Brahe made precise Brahe made precise observations about observations about MarsMars. . Later in life he found and Later in life he found and assistant by the name of assistant by the name of Johannes Kepler.Johannes Kepler.

______________________

Discovered three ___________.Discovered three ___________. Astronomical unit – distance from the Astronomical unit – distance from the

Earth to the sun or 150,000 Earth to the sun or 150,000 kilometerskilometers

Three Laws of Planetary Three Laws of Planetary MotionMotion

All orbits are All orbits are ______________________ in in shapeshape

An An ______________________ is is an almost an almost perfect circleperfect circle

______________________ Law LawEach of these Each of these

triangles are equal triangles are equal in areain area

Can you understand Can you understand the Earth travels the Earth travels faster as it gets faster as it gets closer to the sun closer to the sun and slower as it and slower as it moves away from moves away from the sun?the sun?

______________________ Law LawThis law ______________________( its year) of any

planet. The base unit of measure is the distance

from the Earth to the sun which equals 1 astronomical unit or (approx. 150, 000,000 km.)

Solar distances can be calculated when the periods of revolution (orbit) are known.

TT22=d=d33

Ex. Using MarsEx. Using Mars

Mars revolution equals 1.88 years Mars revolution equals 1.88 years

The square of this is 3.54The square of this is 3.54

The cube root of this is 1.52 The cube root of this is 1.52

This means that Mars is 1.52 a.u. from This means that Mars is 1.52 a.u. from the sun.the sun.

Using the formula another Using the formula another way…way…

If you take the distance in a.u. and If you take the distance in a.u. and cube it.cube it.

Then take the square root of that Then take the square root of that number, you will calculate the period number, you will calculate the period of revolution of the orbiting body.of revolution of the orbiting body.

Ex. Jupiter is approx. 5 a.u. from the Ex. Jupiter is approx. 5 a.u. from the sun sun # 3 then take square root

5533 = 125 125 = = 125 125 = 11.3 11.3 yearsyears

______________________

His most important contributions His most important contributions were his descriptions of the behavior were his descriptions of the behavior of moving objects.of moving objects.

1609 Galileo heard of a Danish lens 1609 Galileo heard of a Danish lens maker who had devised a system of maker who had devised a system of lenses that could magnify objects.lenses that could magnify objects.

Without ever seeing a telescope Without ever seeing a telescope Galileo constructed his own. Galileo constructed his own.

With the aid of his telescope Galileo With the aid of his telescope Galileo discovered:discovered:

1. Four satellites orbiting Jupiter. Today 1. Four satellites orbiting Jupiter. Today these moons are called Galiliean moons. these moons are called Galiliean moons. This discovery proved that objects were This discovery proved that objects were orbiting another body besides the Earth. orbiting another body besides the Earth.

2. Planets are circular disks. It was believed 2. Planets are circular disks. It was believed they were only points of light.they were only points of light.

3. Venus has phases just like the moon.3. Venus has phases just like the moon. 4. The moon’s surface was not smooth.4. The moon’s surface was not smooth. 5. The sun had spots.5. The sun had spots.

______________________

Scientists of the time wondered Scientists of the time wondered about two points:about two points:

1. What causes a moving object to 1. What causes a moving object to continue to move.continue to move.

2. What force keeps the bodies in 2. What force keeps the bodies in space from traveling in a straight space from traveling in a straight line out into space.line out into space.

Although others had theorized the Although others had theorized the existence of such a force, existence of such a force, Newton Newton was the first to formulate and was the first to formulate and test the law of universal test the law of universal gravitation.gravitation.

According to Newton, every body in the According to Newton, every body in the universe attracts every other body with a universe attracts every other body with a force that is directly proportional to their force that is directly proportional to their masses and inversely proportional to the masses and inversely proportional to the square of the distance between their square of the distance between their centers of mass.centers of mass.

Example: The gravitational force decreases Example: The gravitational force decreases with distance, so that two objects 3 with distance, so that two objects 3 kilometers apart have 32, or 9, times less kilometers apart have 32, or 9, times less gravitational attraction than if the same gravitational attraction than if the same objects were 1 kilometer apart.objects were 1 kilometer apart.

The greater the mass of the object, The greater the mass of the object, the greater is its gravitational the greater is its gravitational force.force.

(discuss the difference between mass (discuss the difference between mass and weight)and weight)

___________ being the total amount of ___________ being the total amount of matter an object contains.matter an object contains.

___________ is the force of gravity upon ___________ is the force of gravity upon an object.an object.

Earth moves forward in its orbit Earth moves forward in its orbit about 30 kilometers per second. about 30 kilometers per second.

During the same second, the force of During the same second, the force of gravity pulls it towards the sun about gravity pulls it towards the sun about 0.5 centimeters. 0.5 centimeters.

Newton concluded that it is the Newton concluded that it is the combination of Earth’s forward combination of Earth’s forward motion and its “falling” motion that motion and its “falling” motion that defines its orbit.defines its orbit.

Newton’s laws of GravityNewton’s laws of Gravity

An An ______________________ (force) in motion (force) in motion will stay in motion until another will stay in motion until another ______________________ (force) acts upon it. (force) acts upon it.

The larger the mass, means that The larger the mass, means that it will have stronger gravity . it will have stronger gravity . (used to calculate escape (used to calculate escape velocities)velocities)

For every action there is an For every action there is an ______________________ & & ______________________ reaction reaction

The Earth-Moon-Sun System The Earth-Moon-Sun System

Stonehenge……. Stonehenge……. Lets take a lookLets take a look

Motions of Earth Motions of Earth

The two main motions of Earth The two main motions of Earth are are ______________________ (spin)(spin) and and ______________________ (orbit) (orbit)..

Revolution is ……..Revolution is ……..

is the motion of a body, such as a is the motion of a body, such as a planet or moon, along a path around planet or moon, along a path around some point in space. some point in space.

Earth’s average speed is 107,000 Earth’s average speed is 107,000 kilometers per hour. kilometers per hour.

Our average distance from the sun is Our average distance from the sun is 150,000,000 kilometers. However, all 150,000,000 kilometers. However, all orbits are elliptical so….orbits are elliptical so….

Earth’s ___________ is when the Earth Earth’s ___________ is when the Earth is closest to the sun about is closest to the sun about 147,000,000 kilometers. This occurs 147,000,000 kilometers. This occurs on January 3rd each year.on January 3rd each year.

Earth’sEarth’s ___________ is when Earth is ___________ is when Earth is at is farthest point from the sun at is farthest point from the sun about 152,000,000 kilometers. This about 152,000,000 kilometers. This occurs on July 4th each year.occurs on July 4th each year.

Is this why we have seasons????????Is this why we have seasons????????

The apparent annual path of the sun The apparent annual path of the sun against the backdrop of the celestial against the backdrop of the celestial sphere is called the ___________. sphere is called the ___________.

The planets and moon travel along The planets and moon travel along the same plane as Earth, so their the same plane as Earth, so their paths on the ___________ lie near the paths on the ___________ lie near the ecliptic.ecliptic.

Earth’s axis ……Earth’s axis ……

is tilted on this plane ___________ to the is tilted on this plane ___________ to the ecliptic. ecliptic.

This tilt creates ___________. This tilt creates ___________.

When the apparent position of the sun When the apparent position of the sun is plotted on the celestial sphere is plotted on the celestial sphere over a period of a year’s time, its over a period of a year’s time, its path intersects the celestial equator path intersects the celestial equator at two points. at two points.

These intersect points are spring These intersect points are spring (March 20 or 21) and fall (Sept. 22 or (March 20 or 21) and fall (Sept. 22 or 23). 23).

When the sun is 23.5When the sun is 23.500 north of the north of the equator….. equator…..

___________ occurs. ___________ occurs. When the sun is 23.5When the sun is 23.500 south of the south of the

equator….. equator…..

___________ occurs.___________ occurs.

Procession Procession

The Earth has another very slow The Earth has another very slow motion called procession, which is a motion called procession, which is a slight movement, over 26,000 years. slight movement, over 26,000 years.

The Earth’s axis traces a circle in The Earth’s axis traces a circle in space similar to the wobble of a space similar to the wobble of a spinning top.spinning top.

At the present time the northern axis At the present time the northern axis points to Polaris, which is referred to points to Polaris, which is referred to as the North Star.as the North Star.

In the year 14,000 our northern axis In the year 14,000 our northern axis will point to Vega, which will then will point to Vega, which will then become our north star. become our north star.

Then in the year 28,000 Polaris will Then in the year 28,000 Polaris will again be our north star.again be our north star.

Rotation …….Rotation …….

Rotation results in day and night.Rotation results in day and night. It has become a standard of It has become a standard of

measuring time. measuring time. Each rotation equals about 24 hours.Each rotation equals about 24 hours.

Notice that it says about 24 hours!Notice that it says about 24 hours!

___________ is the time it takes for the ___________ is the time it takes for the Earth to make one complete rotation Earth to make one complete rotation (360 degrees) with respect to a star (360 degrees) with respect to a star other than our sun. other than our sun.

A A sidereal daysidereal day is equal to is equal to ______________________ hours hours ______________________ minutes and minutes and ______________________ seconds seconds. .

___________ is good for determining ___________ is good for determining time.time.

Sidereal is used to determine the Sidereal is used to determine the ___________ Earth is to be at the ___________ Earth is to be at the beginning of each season.beginning of each season.

Earth-Sun Motion Earth-Sun Motion

The Earth, sun, and the rest of the The Earth, sun, and the rest of the solar system travel through space at solar system travel through space at a speed of 20 kilometers per second a speed of 20 kilometers per second towards the star, Vega.towards the star, Vega.

Our solar system also revolves Our solar system also revolves around the galaxy. around the galaxy.

The trip takes 230 million years and The trip takes 230 million years and travels at speeds approaching 250 travels at speeds approaching 250 kilometers per second. kilometers per second.

Galaxies are also in motion. Galaxies are also in motion. Earth is presently approaching the Earth is presently approaching the

Great Galaxy in Andromeda.Great Galaxy in Andromeda.

Motions of the Earth-Moon Motions of the Earth-Moon System System

Average distance to the moon is Average distance to the moon is 384,401 kilometers.384,401 kilometers.

___________ (farthest point in its orbit) ___________ (farthest point in its orbit) and ___________(closest point in its and ___________(closest point in its orbit).orbit).

Lunar phases are a result of the Lunar phases are a result of the motion of the moon and the sunlight motion of the moon and the sunlight that is reflected from its surface. that is reflected from its surface.

Lunar Motions Lunar Motions The moon cycle of phases takes The moon cycle of phases takes

______________________ days days.. One orbit of the moon around the earth One orbit of the moon around the earth

takes ___________ takes ___________ daysdays One rotation on the moon takes One rotation on the moon takes

______________________ days days

Something doesn’t seem to add Something doesn’t seem to add up!!!!!!!!!!!!!up!!!!!!!!!!!!!

What does this all mean????What does this all mean????

If the orbit and rotation of the moon If the orbit and rotation of the moon are the same (27.3 days), that means?are the same (27.3 days), that means?

______________________ Why then does it take the moon Why then does it take the moon

longer to go through its phases?longer to go through its phases?

It must “___________” to where the It must “___________” to where the ___________ to be since the Earth is ___________ to be since the Earth is orbiting the sun.orbiting the sun.

Because the moon must catch up to the Earth each day, it rises

50 minutes later each night.

Phases of the MoonPhases of the Moon

Phases result from the motion of the Phases result from the motion of the moon and the sunlight that is reflected.moon and the sunlight that is reflected.

For the purposes of this class we will For the purposes of this class we will only use the following phases:only use the following phases:

___________ - dark___________ - dark

___________ – lighted side grows larger___________ – lighted side grows larger___________ ___________ ___________ – shadowed side grows larger___________ – shadowed side grows larger

Eclipses Eclipses

Two types:Two types:• ________________• ________________

________________ occur with occur with new moonnew moon phase phase ________________ occur with occur with full moonfull moon.. During a new-moon or full moon phase, During a new-moon or full moon phase,

the moon’s orbit must cross the plane of the moon’s orbit must cross the plane of the ecliptic for an eclipse to occur.the ecliptic for an eclipse to occur.

There are usually There are usually ________________ that occur in that occur in two sets. One lunar and then a solar, two sets. One lunar and then a solar, then 6 months later another lunar and then 6 months later another lunar and solar. solar.

During any given year there are During any given year there are not not more than more than ________________ eclipses. eclipses.

Solar eclipses last about 7 minutes in Solar eclipses last about 7 minutes in any given area. any given area.

The size of the shadow is The size of the shadow is approximately 275 kilometers wide or approximately 275 kilometers wide or about the size of South Carolina. (FYI)about the size of South Carolina. (FYI)

The next total solar eclipse will occur The next total solar eclipse will occur August 21, 2017.August 21, 2017.

Earth’s Moon Earth’s Moon

Moon characteristics: Moon characteristics: Size 3475 kms. Or about Size 3475 kms. Or about ________________

that of Earththat of Earth 6 Apollo missions landed on the 6 Apollo missions landed on the

moon between 1969 and 1972moon between 1969 and 1972 Moon’s density is 3.3 which is less Moon’s density is 3.3 which is less

than the 5.5 of Earth rocks.than the 5.5 of Earth rocks. Gravity is Gravity is ________________ of Earth of Earth

Lunar Surface Lunar Surface

No volcanismNo volcanism ________________ – most craters were produced by – most craters were produced by

the impact of rapidly moving debris.the impact of rapidly moving debris. A meteoroid 3 meters in diameter can make A meteoroid 3 meters in diameter can make

a crater 150 meters wide. a crater 150 meters wide. Larger craters like Kepler and Copernicus Larger craters like Kepler and Copernicus

were formed with the impact of bodies 1 were formed with the impact of bodies 1 kilometer or more in diameter.kilometer or more in diameter.

________________ – debris splash marks near the – debris splash marks near the crater.crater.

Rays with cratersRays with craters

________________ – or mountain peaks. – or mountain peaks. The highest is near 8 kilometers in The highest is near 8 kilometers in

height or just 1 kilometer short of Mt. height or just 1 kilometer short of Mt. Everest.Everest.

________________ – (seas) name by – (seas) name by Galileo Galileo

Relatively dark smooth areas on the moon’s Relatively dark smooth areas on the moon’s surface. surface.

Maria formed from ancient beds of basaltic Maria formed from ancient beds of basaltic lava, originated when asteroids punctured lava, originated when asteroids punctured the lunar surface, letting magma bleed out. the lunar surface, letting magma bleed out.

These lava flows are often 30 meters thick. These lava flows are often 30 meters thick. Long channels called Long channels called ________________ are are

associated with maria. They may be the associated with maria. They may be the remains of ancient lava flows or lava tunnels remains of ancient lava flows or lava tunnels then caved in. then caved in.

________________ – lunar regolith, which is a – lunar regolith, which is a soil like layer on the moon. It is soil like layer on the moon. It is composed of igneous rocks, glass composed of igneous rocks, glass beads, and fine lunar dust.beads, and fine lunar dust.

Lunar History Lunar History

Most accepted lunar formation model:Most accepted lunar formation model: The origin of the moon occurred The origin of the moon occurred

when the solar system was forming, when the solar system was forming, a body the size of Mars impacted the a body the size of Mars impacted the Earth. Earth.

A portion of the liquefied material A portion of the liquefied material entered Earth’s orbit where it entered Earth’s orbit where it combined to form the moon. combined to form the moon.

EvidenceEvidence

1. Ejected material would have been 1. Ejected material would have been iron poor and so is the moon. iron poor and so is the moon.

2. The ejected material would have 2. The ejected material would have stayed in orbit long enough to loose stayed in orbit long enough to loose its water.its water.

The moon evolved in three stages:The moon evolved in three stages: The original crust meaning The original crust meaning ________________ mariamaria basins basins rayed cratersrayed craters

Continued impact of meteoroids Continued impact of meteoroids combined with radioactive decayed combined with radioactive decayed materials, generated enough heat to materials, generated enough heat to melt the moon’s outer shell and melt the moon’s outer shell and possibly the inner as well. possibly the inner as well.

The highland areas are estimated to The highland areas are estimated to be 4.5 billion years old.be 4.5 billion years old.

The maria basins are younger than The maria basins are younger than the highlands and in some places the highlands and in some places over lap some highland areas. over lap some highland areas.

The last features to form were the The last features to form were the rayed craters. rayed craters.

Most of the Most of the old craters are ray-old craters are ray-lessless. .