The Earth in Space. A.Observations of Celestial Objects Some important terms: Celestial Sphere -

transcript

The Earth in Space

A. Observations of Celestial Objects

Some important terms:

Celestial Sphere -

Celestial Sphere – a model of the sky – an imaginary sphere upon which celestial (“heavenly”) objects are “attached”.

Altitude

Altitude - the angle above the horizon.*

Altitude - the angle above the horizon.

Zenith -

Zenith – an altitude of 90 o (directly overhead)

Azimuth –

Azimuth – an angle clockwise from north. N

What would be the location of the star?

What would be the location of the star? Altitude 45o, azimuth 30o.

What is going on in this picture?

These all show star trails, the apparent paths that the stars make around Polaris during the night.

1. Apparent Motion of Celestial Objects

a. Star trails - the apparent paths that the stars make around Polaris during the night.

Polaris(the one that doesn’t appear to move)

a. Star trails - the apparent paths that the stars make around Polaris during the night. The paths are circular and appear to move at 15 o per hour.

Polaris(the one that doesn’t appear to move)

b. Annual Motion – stars appear to move slowly westward as we go through the year.

b. Annual Motion – stars appear to move slowly westward as we go through the year. Different constellations are visible at different seasons.

Orion rising at 8:30 PM on Nov. 1st

b. Annual Motion – stars appear to move slowly westward as we go through the year. Different constellations are visible at different seasons.

(The Zodiac constellations are the ones that appear to move through the sun’s path as the seasons progress.)

2. Apparent Planetary Motions

2. Apparent Planetary Motionsa. Planets (“wanderers” in Greek) appear to

move in non-uniform paths, which include retrograde (backwards) motion.

b. Their diameters vary in a cyclic manner.

b. Their diameters vary in a cyclic manner. (They appear big, then small, then big …)

b. Their diameters vary in a cyclic manner. (They appear big, then small, then big …) They are closer to earth, then farther away, then closer…

c. Planets rotate (most in the same direction as Earth).

d. Some planets have satellites (moons).

3. Earth – Moon Motions

3. Earth – Moon Motionsa. The moon’s apparent diameter varies in a

cyclic manner.

b. The moon goes through a cycle of phases.

cyclic manner.

b. The moon goes through a cycle of phases.1. It takes 29.5 days to go

from full to full.

cyclic manner.

from full to full. 2. It takes 27.3 days to orbit the earth.

cyclic manner.

Lunar Month

Sidereal Month

cyclic manner.

c. The moon rises about an hour later each day.

Lunar Month

Sidereal Month

cyclic manner.

d. Ocean tides change in a cyclic manner, and vary in range

Lunar Month

Sidereal Month

cyclic manner.

d. Ocean tides change in a cyclic manner, and vary in range (Spring tides are extra high & extra low; Neap tides are medium high & medium low)

Lunar Month

Sidereal Month

cyclic manner.

d. Ocean tides change in a cyclic manner, and vary in range (Spring tides are extra high & extra low; Neap tides are medium high & medium low) in step with the phases.

Lunar Month

Sidereal Month

3. Earth – Moon Motionse. Eclipses occur in a cyclic manner,

3. Earth – Moon Motionse. Eclipses occur in a cyclic manner, but, as viewed from earth, vary as to where they’re seen

3. Earth – Moon Motionse. Eclipses occur in a cyclic manner, but, as viewed from earth, vary as to where they’re seen and in degree of totality.

Solar eclipse: when the moon comes between the sun and the earth.

Solar eclipse:

Lunar eclipse – when the earth comes between the sun and the moon.

Earth’s Motions

1.Rotation – turning on its axis2.Revolution – orbiting the Sun3.Precession – slight movement of the Earth’s axis over a long period of time. Precession is the slow, top-like wobbling of the spinning Earth, with a period of about 26,000 years.

4. Nutation – wobble in the movement of Earth’s

precession; a small oscillation with a period of 18.6 years and an amplitude of 9.2 seconds of arc on the precession; The Moon causes this wobble.

Barycenter

The Earth doesn’t stay in position as the Earth orbits it; instead, the moon as well as the Earth orbit the barycenter between the two celestial bodies. The barycenter is the center of mass of a system, in this case the Earth-Moon system. It’s barycenter lies about 1700km beneath the Earth’s surface (not at the center of the Earth).

4. Apparent Motions of the Sun

4. Apparent Motions of the Suna. Rising and setting of the sun varies in time

and location throughout the year.

4. Apparent Motions of the Suna. Rising and setting of the sun varies in time

and location throughout the year.

4AM8AM

b. The sun appears to make a circular path around the celestial sphere (ecliptic) each year,

b. The sun appears to make a circular path around the celestial sphere (ecliptic) each year, going through all 12 constellations of the zodiac.

c. The sun’s diameter varies throughout the year.

d. The sun can only be seen at zenith if you are located between 23.5o N and 23.5o S.

c. The sun’s diameter varies throughout the year.

d. The sun can only be seen at zenith if you are located between 23.5o N and 23.5o S.

d. The sun appears to rotate once every 27 days.

(Galileo first discovered this by timing the movement of sunspots.)

d. The sun appears to rotate once every 27 days.

(Galileo first discovered this by timing the movement of sunspots.)

Seasons and the Sun:

Earth-Sun Relations.url

– Autumnal Equinox – 1st day of Fall -

– Autumnal Equinox – 1st day of Fall – Sept. 23 -

– Autumnal Equinox – 1st day of Fall – Sept. 23 – direct rays of the sun hit the (the sun is at zenith on the)

– Autumnal Equinox – 1st day of Fall – Sept. 23 – direct rays of the sun hit the (the sun is at zenith on the) equator -

– Autumnal Equinox – 1st day of Fall – Sept. 23 – direct rays of the sun hit the (the sun is at zenith on the) equator – the noon sun is on the horizon at the poles -

– Autumnal Equinox – 1st day of Fall – Sept. 23 – direct rays of the sun hit the (the sun is at zenith on the) equator – the noon sun is on the horizon at the poles – everywhere on earth gets 12 hours of sunlight -

– Autumnal Equinox – 1st day of Fall – Sept. 23 – direct rays of the sun hit the (the sun is at zenith on the) equator – the noon sun is on the horizon at the poles – everywhere on earth gets 12 hours of sunlight – the sun rises due east and sets due west.

- Winter Solstice – 1st day of Winter -

- Winter Solstice – 1st day of Winter – Dec. 21 -

- Winter Solstice – 1st day of Winter – Dec. 21 – direct rays hit the Tropic of Capricorn -

- Winter Solstice – 1st day of Winter – Dec. 21 – direct rays hit the Tropic of Capricorn – the Arctic Circle is in constant darkness,

- Winter Solstice – 1st day of Winter – Dec. 21 – direct rays hit the Tropic of Capricorn – the Arctic Circle is in constant darkness, the Antarctic Circle is in constant light -

-Winter Solstice – 1st day of Winter – Dec. 21 – direct rays hit the Tropic of Capricorn – the Arctic Circle is in constant darkness, the Antarctic Circle is in constant light – NYS has its lowest noon solar altitude & shortest daylight period -

-Winter Solstice – 1st day of Winter – Dec. 21 – direct rays hit the Tropic of Capricorn – the Arctic Circle is in constant darkness, the Antarctic Circle is in constant light – NYS has its lowest noon solar altitude & shortest daylight period – sun rises in the southeast and sets in the southwest

Vernal Equinox – 1st day of Spring -

Vernal Equinox – 1st day of Spring – March 21

Vernal Equinox – 1st day of Spring – March 21 – Same as the Autumnal Equinox

Summer Solstice – 1st day of summer -

Summer Solstice – 1st day of summer – June 21 -

Summer Solstice – 1st day of summer – June 21 – the direct rays of the sun hit the Tropic of Cancer

Summer Solstice – 1st day of summer – June 21 – the direct rays of the sun hit the Tropic of Cancer – areas in the Arctic Circle get 24 hours of daylight -

Summer Solstice – 1st day of summer – June 21 – the direct rays of the sun hit the Tropic of Cancer – areas in the Arctic Circle get 24 hours of daylight – areas within the Antarctic Circle get 24 hour of darkness -

Summer Solstice – 1st day of summer – June 21 – the direct rays of the sun hit the Tropic of Cancer – areas in the Arctic Circle get 24 hours of daylight – areas within the Antarctic Circle get 24 hour of darkness – NYS gets the most hours of daylight (16) and the sun reaches its highest noontime altitude.

Summer Solstice – 1st day of summer – June 21 – the direct rays of the sun hit the Tropic of Cancer – areas in the Arctic Circle get 24 hours of daylight – areas within the Antarctic Circle get 24 hour of darkness – NYS gets the most hours of daylight (16) and the sun reaches its highest noontime altitude. Sunrise is in the northeast and sunset is in the northwest.

a. Solar day – the time it takes for the sun to go from noon

a. Solar day – the time it takes for the sun to go from noon (directly above the meridian - -

a. Solar day – the time it takes for the sun to go from noon (directly above the meridian - - in NYS due south)

a. Solar day – the time it takes for the sun to go from noon (directly above the meridian - - in NYS due south) to the next noon.

a. Solar day – the time it takes for the sun to go from noon (directly above the meridian - - in NYS due south) to the next noon. This varies during the year;

a. Solar day – the time it takes for the sun to go from noon (directly above the meridian - - in NYS due south) to the next noon. This varies during the year; it’s not always 24 hours.

a. Solar day – the time it takes for the sun to go from noon (directly above the meridian - - in NYS due south) to the next noon. This varies during the year; it’s not always 24 hours. That’s why our clocks are set according to mean solar time.

b. Sidereal day (star day)

b. Sidereal day (star day) – the actual time it takes for the earth to rotate once.

b. Sidereal day (star day) – the actual time it takes for the earth to rotate once. It is based on using a star as a reference point.

b. Sidereal day (star day) – the actual time it takes for the earth to rotate once. It is based on using a star as a reference point. 1 sidereal day = 23 hr, 56 min.

c. One year is the time it takes to go from

c. One year is the time it takes to go from one vernal equinox to the next.

c. One year is the time it takes to go from one vernal equinox to the next. One year =365 ¼ days.

What terrestrial (land or earth) based evidence is there to support the idea that the earth moves?

What terrestrial (land or earth) based evidence is there to support the idea that the earth moves?1. Foucault’s Pendulum – a very long pendulum allowed to swing freely for a long time

What terrestrial (land or earth) based evidence is there to support the idea that the earth moves?1. Foucault’s Pendulum – a very long pendulum allowed to swing freely for a long time will appear to change direction.

2. Coriolis Effect – the path of a fluid at the earth’s surface appears to be deflected

2. Coriolis Effect – the path of a fluid at the earth’s surface appears to be deflected (to veer off) to the right in the N. hemisphere instead of going straight.

2. Coriolis Effect – the path of a fluid at the earth’s surface appears to be deflected (to veer off) to the right in the N. hemisphere instead of going straight. Original

Deflected path

If you were standing in the middle and looked along any line, they each would appear to have bent to the right.

e.g. water draining makes a whirlpool

e.g. winds blow clockwise around a high pressure area and counterclockwise around a low

What models of our solar system explain the observations of celestial & terrestrial motions?

What models of our solar system explain the observations of celestial & terrestrial motions?GEOCENTRIC MODEL (earth-centered)

Aristotle (384-322 B.C.)Earth made up of 4 elements: earth, fire water and airConcluded Earth is round because it always casts a curved shadowUniverse is made of 55 celestial spheresEach sphere rotates Outside sphere is the “prime mover” that caused the rotation

What models of our solar system explain the observations of celestial & terrestrial motions? GEOCENTRIC MODEL

Aristarchus (312-230 B.C.)Used geometry to calculate relative distances from Earth to the sun and from the Earth to the moonCalculated the sizes of the sun and moon but was way off

What models of our solar system explain the observations of celestial & terrestrial motions?Geocentric Model

Eratosthenes (276-194 B.C.)•1st to measure the circumference of the Earth•He measured 39,400km (actual is 40,075km!)

Geocentric Model

Hipparchus (2nd Century B.C.)•Determined the location of almost 850 stars which he divided into 6 categories based on their brightness•Measured the length of the year to within minutes of modern year•Developed method for predicting times of lunar eclipses to within a few hours

What models of our solar system explain the observations of celestial & terrestrial motions? GEOCENTRIC MODEL (Earth centered) – Ptolemy

What models of our solar system explain the observations of celestial & terrestrial motions?I. GEOCENTRIC MODEL (Earth centered) –

Ptolemy

a. The apparent motions can be explained,

Ptolemy

a. The apparent motions can be explained, but some of the objects would have very strange motions in order to match the observations.

Ptolemy

a. The apparent motions can be explained, but some of the objects would have very strange motions in order to match the observations. For instance, planets would have orbits that include epicycles.

b. Problems with the Geocentric Model:

1. It does not predict future locations well.

2. It does not account for terrestrial motions.

2. It does not account for terrestrial motions. (Foucault’s pendulum & Coriolis Effect)

II. HELIOCENTRIC MODEL

II. HELIOCENTRIC MODEL (Sun centered)

Copernicus (A.D. 1473-1543)

II. HELIOCENTRIC MODEL (Sun centered) – Copernicus a. The apparent motions of celestial objects

can be explained,

can be explained, and the planets’ motions are very simple.

Mercury

1. The sun is at the center.

2. The planets (including Earth) orbit the sun.

2. The planets (including Earth) orbit the sun. Revolution and tilt combine to cause seasons.

3. The planets all rotate

3. The planets all rotate (day and night.)

4. The moon orbits Earth

4. The moon orbits Earth (phases, tides and eclipses).

4. The moon orbits Earth (phases, tides and eclipses).b. Terrestrial motions CAN be explained

(rotation).

4. The moon orbits Earth (phases, tides and eclipses).b. Terrestrial motions CAN be explained

(rotation).

c. It’s better at predicting celestial locations.

Improving the Heliocentric Model

Mercury

Tycho Brahe

• A.D. 1546-1601• Most precise observations with the best

instruments available prior to telescope • Observations of planetary motion led to our

current model of the solar system• Observed a comet in 1577• Used parallax to prove distance

Johannes Kepler discovered that the planets followed elliptical orbits,

Johannes Kepler discovered that the planets followed elliptical orbits, with the sun acting as one focus.

Eccentricity – how far from circular the ellipse is.

More eccentric

Less eccentric

Johannes Kepler discovered that the planets followed elliptical orbits, with the sun acting as one focus. (1st Law) Eccentricity – how far from circular the ellipse is.

Focal distance

. .The greater the focal distance, the more

eccentric the ellipse.

Formula for finding eccentricity:

Eccentricity = distance between foci

length of major axis

Kepler also found that the orbital velocities of the planets change; the farther a planet is from the sun, the slower it orbits

Kepler also found that the orbital velocities of the planets change; the farther a planet is from the sun, the slower it orbits (e.g. Mercury orbits faster than Neptune;

See “Gravitation 3.8 …” web site

Kepler also found that the orbital velocities of the planets change; the farther a planet is from the sun, the slower it orbits (e.g. Mercury orbits faster than Neptune; Earth moves slower during our summer than during our winter).

See “Planetary Motion…” web site.

perihelion – when a planet is closest to the sun

perihelion – when a planet is closest to the sun aphelion – when a planet is farthest from the sun

The “Law of Equal Areas” says that the area of space swept out by a line drawn between a planet and its sun

The “Law of Equal Areas” says that the area of space swept out by a line drawn between a planet and its sun will be equal to any other area swept by the same planet for the same amount of time. (2nd Law)

Area for day 24

Area for day 12

He discovered the calculation for the amount of time (in Earth years) a planet takes to orbit the Sun. (3rd Law)

The planet’s orbital period squared is equal to its mean solar distance cubed:

T2 = d3

Galileo studied falling objects and discovered that

Galileo studied falling objects and discovered that all things fall at the same rate, despite their weight.

. Both objects fell at the same rate.

Galileo studied falling objects and discovered that all things fall at the same rate, despite their weight. He showed that it was only friction that slowed things down, some more than others.

Galileo studied falling objects and discovered that all things fall at the same rate, despite their weight. He showed that it was only friction that slowed things down, some more than others. He also showed that objects speed up the longer they fall.

Galileo studied falling objects and discovered that all things fall at the same rate, despite their weight. He showed that it was only friction that slowed things down, some more than others. He also showed that objects speed up the longer they fall. He suggested that satellites actually fall toward their planet, but that they have so much speed that they keep missing it.

Direction of movement (inertia)

Pull of gravity

Direction of movement (inertia)

Pull of gravity

Resulting motion

Galileo also …… was the first person to use the telescope for astronomy… discovered that the Sun had dark patches that we now call sunspots… discovered that the 4 points of light near Jupiter were actually moons that orbited Jupiter… discovered that Venus has phases just like the moon… discovered that the Moon’s surface isn’t smooth

Isaac Newton (A.D. 1642-1727) developed the “Universal Law of Gravitation”,

Isaac Newton developed the “Universal Law of Gravitation”, which states that gravity extends out into space, and that all objects that have mass have gravitational pull.

Earth pulls on the moon

The moon pulls on Earth.

They both pull on each other.

The force of gravitational attraction depends on the masses of the two objects,

More mass, more pull.

Less mass, less pull.

The force of gravitational attraction depends on the masses of the two objects, and the distance between them.

Less distance, more pull.

More distance, less pull.

The force of gravitational attraction depends on the masses of the two objects, and the distance between them. If you double the distance, the force of attraction becomes ¼ of the original force.

More distance, less pull.

The force of gravitational attraction depends on the masses of the two objects, and the distance between them. If you double the distance, the force of attraction becomes ¼ of the original force. If you cut the distance to 1/3, then the force becomes 9 times stronger. He discovered that acceleration due to Earth’s gravity is 9.8m/s/s.

Less distance, more pull.

Newton also…… developed 3 Laws of Motion that explain all motion whether on Earth or in the Heavens… invented calculus (boo!) and the Newtonian telescope… rewrote Kepler’s 3rd Law to account for the mass of the body orbiting a satellite

Albert Einstein (1879-1955)

Developed the General Theory of Relativity which states that the presence of mass curves space.

Developed the Special Theory of Relativity which states that the speed of light (300,000km/s) is an important constant that cannot be exceeded.

Found that energy of a system is equal to the mass of the system times the speed of light squared, or

E = mc2

Assignment

• Create a poster timeline of major astronomical discoveries. Include information on who discovered them and when. Include any other interesting information about the discovery or it’s contribution to astronomy. Illustrate your timeline and make it interesting to look at.

We can learn much about stars (and other celestial objects) by examining their radiation.

We can learn much about stars (and other celestial objects) by examining their radiation. For example, the color of the star’s light indicates its temperature.

- Indicates a cool temperature.

- Indicates a hot temperature.

Our sun is a star of average temperature.

When stars are moving, their wavelengths get shifted.

When stars are moving, their wavelengths get shifted. (This is called a Doppler Shift.)

When stars are moving, their wavelengths get shifted. (This is called a Doppler Shift.) If it shifts to the red, it means that the star is moving away from us.

When stars are moving, their wavelengths get shifted. (This is called a Doppler Shift.) If it shifts to the red, it means that the star is moving away from us. If it shifts to the blue, it is moving toward us.

Because the vast majority of stars that we see all around us have a red shift, we believe the universe is expanding.

Because the vast majority of stars that we see all around us have a red shift, we believe the universe is expanding.This also leads to the belief that the universe started from one central location,

Because the vast majority of stars that we see all around us have a red shift, we believe the universe is expanding.This also leads to the belief that the universe started from one central location, from one small point,

Because the vast majority of stars that we see all around us have a red shift, we believe the universe is expanding.This also leads to the belief that the universe started from one central location, from one small point, and erupted with a huge explosion:

Because the vast majority of stars that we see all around us have a red shift, we believe the universe is expanding.This also leads to the belief that the universe started from one central location, from one small point, and erupted with a huge explosion: “The Big Bang”

There are many theories as to how the galaxies,.

There are many theories as to how the galaxies, stars

There are many theories as to how the galaxies, stars and planets formed.

There are many theories as to how the galaxies, stars and planets formed. One popular theory states that matter (mostly hydrogen) started to pull together, forming a huge cloud.

There are many theories as to how the galaxies, stars and planets formed. One popular theory states that matter (mostly hydrogen) started to pull together, forming a huge cloud. This is called a nebula.

There are many theories as to how the galaxies, stars and planets formed. One popular theory states that matter (mostly hydrogen) started to pull together, forming a huge cloud. This is called a nebula. The nebula continued to collapse and spin.

There are many theories as to how the galaxies, stars and planets formed. One popular theory states that matter (mostly hydrogen) started to pull together, forming a huge cloud. This is called a nebula. The nebula continued to collapse and spin. Most of the gas and dust collected in the center to form the sun.

There are many theories as to how the galaxies, stars and planets formed. One popular theory states that matter (mostly hydrogen) started to pull together, forming a huge cloud. This is called a nebula. The nebula continued to collapse and spin. Most of the gas and dust collected in the center to form the sun. The small amount of left over material orbiting the sun formed the planets.

Some things you may see in space:

The Hale Telescope at Mt. Palomar

Radio telescope with comet Ikeya – Zhang in background

Hubble Telescope

Asteroid Gaspra

Jupiter with moons Io and Europa

Jupiter with the Great Red Spot

Saturn

An inside look at the rings

Uranus

Uranus with rings

Neptune

Pluto and Charon

Two moons discovered near Pluto

Comet Halle-Bopp

Comet Halley 1986

A closer view of Comet Halley without the tail

The Milky Way Galaxy

The Milky Way

You are here

Our nearest neighboring star system - Alpha Centauri

Binary star system.They orbit each other every 321 seconds.

This binary system has one star that has reached red giant stage, with its outer gases being pulled by the companion star.

Horsehead Nebula

The Dumbbell Nebula

The Crab Nebula

The Trifid Nebula

The Angel Nebula

The Veil Nebula

The Great Nebula in Orion

Andromeda Galaxy

A globular cluster galaxy

Supernova 1987

Supernova 1994 D

Supernova 1054

The Earth in Space. A.Observations of Celestial Objects Some important terms: Celestial Sphere -

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