chapter 19 the solar system. sun, earth, and moon the position of objects in the sky change over...

Chapter 19The Solar System

Sun, Earth, and Moon

• The position of objects in the sky change over time because Earth, and everything else in the universe, is constantly moving.– Earth’s spinning on its axis and orbiting the sun

create apparent movement in the sky• A planet is a celestial body that orbits the

sun, is round because of its own gravity, and has cleared the area around its orbital path.


http://2.bp.blogspot.com/-G-JHD7WEXd4/TzLe5YHsgSI/AAAAAAAAFio/0R0ep0Pvrro/s1600/eso1208a.jpg


• The sun is the closest star to Earth– Is an average star– Has a mass about

330,000 times Earth

http://en.wikipedia.org/wiki/File:The_Sun_by_the_Atmospheric_Imaging_Assembly_of_NASA%27s_Solar_Dynamics_Observatory_-_20100819.jpg

Sun, Earth, and Moon• The Sun is the star at the center of the Solar System. It is

almost perfectly spherical and consists of hot plasma interwoven with magnetic fields. It has a diameter of about 1,392,684 km (865,374 mi), around 109 times that of Earth, and its mass (1.989×1030 kilograms, approximately 330,000 times the mass of Earth) accounts for about 99.86% of the total mass of the Solar System. Chemically, about three quarters of the Sun's mass consists of hydrogen, while the rest is mostly helium. The remainder (1.69%, which nonetheless equals 5,600 times the mass of Earth) consists of heavier elements, including oxygen, carbon, neon and iron, among others.


• The Sun formed about 4.567 billion years ago from the gravitational collapse of a region within a large molecular cloud. Most of the matter gathered in the center, while the rest flattened into an orbiting disk that would become the Solar System. The central mass became increasingly hot and dense, eventually initiating thermonuclear fusion in its core. It is thought that almost all stars form by this process.


• The sun is a major external source of heat and light for Earth– As the earth turns on its axis every 24 hours, we

see the sun rise and set– Many patterns of animal behavior follow the

sun’s cycle– Effects the weather and ocean currents– Effects the seasons– Promotes plant life


• Planets and distant stars are visible in the night sky– Greek scholars saw and gave names to patterns

http://www.thespacewriter.com/skylarge.jpg

http://www.physics.unlv.edu/~jeffery/astro/constellation/constellation_north.html


• Family of Planets: the solar system is the sun and all of the objects that orbit it– 8 planets and their moons– Dwarf planet– Asteroids– Comets– Dust– Gas


• Gravity holds the solar system together– Every object in the solar system pulls on every

other object• The force of gravity between two objects depends

upon their masses and the distance between them– The sun exerts the largest force in the solar

system because its mass is so large• The pull of the sun keeps Earth in its orbit• Gravity is the force that keeps moons orbiting around

planets


• Eight planets orbit the Sun: a planet’s distance from the sun determines how long the planet takes to orbit the sun– Mercury: the closest, 88 days– Earth: 365.25 days– Neptune: the most distant: 165 years (60,225

days)


http://en.wikipedia.org/wiki/File:Planets2013.jpg


http://www.redorbit.com/media/uploads/2004/10/6_15cc05865f89c4801c5ff2a85d74a93c2.jpg


• A satellite is an object in orbit around a body that has a larger mass.– The moon is Earth’s satellite– All of the planet’s in our solar system except Mercury

and Venus have moons– Currently there are 135 known satellites (moons)

orbiting the planets• Some are as small as 3km in diameter to as large as Mercury

– Can be seen because of the light they reflect


http://en.wikipedia.org/wiki/File:Moons_of_solar_system_v7.jpg


• The Moon:– Orbits the Earth at a distance of about 384,000

km– Like the Sun, the moon affects life on Earth

through its movements and gravitational influence


• The moon appears to have different shapes throughout the month that are called phases– As the Moon revolves around Earth, the

illuminated portion of the Moon that faces Earth changes.

• When the Moon is new, the side that is dark is facing you, so you cannot see it

• The time from one full Moon to the next is 29.5 days


• The Moon Phases as viewed from Earth An easy way to remember the phases of the moon is to think of "DOC"! On the first night of the lunar month ("month") the moon is not visible, this phase is called the new moon.


http://www.easttennesseewildflowers.com/gallery/index.php/moon/Moon_phases_earthview


• The sun is shining on the back side (what we call the "dark side" of the moon) which can't be seen from our vantage point. We always see the same side of the moon because it rotates so slowly the same face is always toward the Earth, fortunately, the side we see is the prettiest! In 3 days a tiny sliver of a waxing crescent can be seen, this is the "D" in "DOC".

Sun, Earth, and Moon• Every night more light is added on the right side

(waxing), making more of the moon's disc visible. One week into the lunar cycle half of the moon is visible (but it is called the 1st Quarter). This is the best phase to view the moon with binoculars or a telescope because it can be seen early in the evening and the craters are well defined by the shadows. It is often possible to see the moon during the afternoon in this phase. On day 12 the moon is almost, but not quite, full. This is the waxing gibbous phase.


• Two weeks into the moon's revolution around the earth we enjoy a big, bright full moon, the "O". Up until this point, the moon has had more light added each night, from here on out, there will be less light each night. By day 16 the light begins to wane to the right and the moon is in the waning gibbous phase.


• Day 21 brings the 3rd Quarter phase when the other half is seen. The moon rises an hour later each night, by day 26 only a tiny crescent is visible early in the morning, this is the "C" phase. On Day 28 the moon has completed its cycle. The rare times that there are 2 full moons in one month, it is called a "Blue Moon".


• The phase of the moon appears the same all over the world, but the orientation changes depending on your latitude. In other words, a full moon will be full all over the world, but its features may appear upside down from the opposite hemisphere. When high in the sky, crescent moons will appear closer to 'vertical' at higher latitudes and 'horizontal' nearer the equator.


• Eclipses are caused by bodies casting a shadow– An eclipse occurs when one object moves into

the shadow cast by another object


• A total solar eclipse requires the umbra of the Moon's shadow to touch the surface of the Earth. Because of the relative sizes of the Moon and Sun and their relative distances from Earth, the path of totality is usually very narrow (hundreds of kilometers across). The following figure illustrates the path of totality produced by the umbra of the Moon's shadow.

Sun, Earth, and Moon• In case of a total solar eclipse, the Moon looks as big as

the Sun, thus covering it completely. For those few precious moments, only the faint halo/ corona of the Sun is visible. This happens when the Earth and the Moon are closest to each other, since then the Moon appears big enough to completely cover the Sun! It is a pretty rare event, not to mention spectacular, and is only for those people who are in the regions falling in the Moon's umbra.


• Total Solar Eclipses occur when the umbra of the Moon's shadow touches a region on the surface of the Earth.


• Partial Solar Eclipses occur when the penumbra of the Moon's shadow passes over a region on the Earth's surface.

Sun, Earth, and Moon• During this eclipse, the Sun and the Moon do not come in

the same straight line. This happens because of the tilt of the Moon's orbit to the Earth's elliptic. In this eclipse, the Moon partly covers the Sun, so it is visible from a large portion of the Earth. In this type of eclipse the umbra of the Moon completely misses the Earth, so no region on Earth will experience a total solar eclipse. Only part of the penumbra covers a few regions of the Earth.


• Annular Solar Eclipses occur when a region on the Earth's surface is in line with the umbra, but the distances are such that the tip of the umbra does not reach the Earth's surface.

Sun, Earth, and Moon• This eclipse is caused when the Sun and the Moon are

positioned in one straight line, but the Moon doesn't completely cover the Sun. During this eclipse, the Moon appears much smaller in size as compared to the Sun. As a result, a bright ring is visible in the sky. This happens when the Earth is farthest away from the Moon, which is why it appears small, and cannot hide the Sun completely. An annular eclipse occurs more frequently than a total eclipse, and needless to say, looks beautiful!

Sun, Earth, and Moon• Safety• Permanent damage will be caused to the retina of the

eye if proper precautions are not taken while observing the Sun. Injuries to the retina can occur without pain and the results may not be noticeable for some hours after the damage has been done. Viewing a partial solar eclipse, annular solar eclipse, or the partial phase of a total solar eclipse should not be attempted without some form of eye protection or the use of an appropriate observing method.

• Never stare at the Sun. Even if only 1% of the Sun's disc is visible, it is still bright enough to cause damage. Children, especially, should be well supervised.


• Left: Total solar eclipse, showing the solar corona and several red prominences around the edge .

• Center: Partial solar eclipse . • Right: Annular solar eclipse, when the moon is too far

away to completely cover the sun


• A lunar eclipse occurs when the moon and sun are on opposite sides of the earth. Often the entire moon is covered by earth's shadow.


• A sequence of three photos of the total lunar eclipse of August 16-17, 1989, taken over a time period of about half an hour. The exposure time was shortest for the bright partial phase (left), and longest for the dark red total phase (right). The middle photo shows how the eclipsed portion of the moon is much darker than the small sliver that's receiving direct sunlight.

Sun, Earth, and Moon• The Moon affects Earth’s tides:

– Most coastal regions on Earth have two high tides and two low tides

– Even though tides are affected by Earth’s landscape, tides are mainly a result of the gravitational influence of the Moon

– Moon’s gravitational pull is strongest on the side of Earth nearest the Moon

• The ocean is pulled toward the Moon, so a slight bulge is created. The solid Earth also moves slightly under the Moon’s gravity, but the movement of water is more noticeable because water is liquid


• Because these external forces of gravity are so great, not only do the oceans bulge out in the direction towards the sun and the moon, but they also want to bulge out in the opposite direction. The result is an almost football like bulge of the oceans when the gravities are aligned. That’s because the Earth is pulled by each of these gravities so forcefully that the planet itself displaces water on the opposite side.


• The earth’s inclination in relation to the sun also effects the tides. The sun’s inclination follows a year-long cycle, and is in highest inclination in the summer and winter months. During these months the "bulges" in the ocean are offset the most from the equator, and it is most likely to encounter only one tide cycle per day, or diurnal tides.


• The highest tides on planet Earth occur near Wolfville, in Nova Scotia's Minas Basin. The water level at high tide can be as much as 16 meters (52 feet) higher than at low tide.

http://bayoffundytourism.com/tides/maps/

http://bayoffundytourism.com/bay_of_fundy_tourism_brochure_2013-2014.pdf?0b754c

The Inner and Outer Planets

• The terrestrial planets are relatively small and have solid, rocky surfaces– Gravity keeps their orbits nearly circular

around the sun– Metallic cores rocky surfaces with some of the

same terrain features as Earth (mountains, canyons, and craters)

The Inner and Outer Planets• Internal structures of the Terrestrial planets. For

Venus, the core must be similar to that of the Earth in comparison to its size, but for Mercury, the core is relatively large in comparison to its size, and for Mars, the core is either relatively small, as shown here, or made of lighter than usual materials. Note that although Mercury's core is "large" in comparison to the size of the planet, it is not large compared to the Earth's core. The Earth's core is larger than Mars, and more than twice as massive as Mars and Mercury combined.

http://universe-review.ca/I07-04-inner2.jpg


• Mercury has extreme temperatures– Mercury is the smallest and closest to the Sun of the

eight planets in the Solar System – Surface can reach as high as 720K to a low of 103K– Rotation: One day is equivalent to nearly 59 Earth days– Orbit: one year is approximately 88 Earth days– No atmosphere– No water

The Inner and Outer Planets• Venus:

– Venus, the second planet from the sun, is named for the Roman goddess of love and beauty

– Thick clouds cause a greenhouse effect– Spins very slowly in a direction opposite that of most other planets

and the Sun– Spin: One day is 243 Earth days– Orbit: 0.6 Earth year

• Therefore, its day is longer than its year– Atmosphere contains large amounts of sulfuric acid and carbon

dioxide (causes greenhouse effect)– Temperature greater than 700K– Surface Pressure is 90x the pressure on Earth


• Earth has ideal conditions for living creatures– Third planet from the Sun– Rotation (spin): 1 day– Orbit: 365 days– Only planet with large amounts of liquid water– Water takes a long time to heat and cool (high

specific heat) helping moderate the temperature of Earth.

The Inner and Outer Planets• Earth’s atmosphere:

– 78% nitrogen, 21% oxygen, and 1% argon, carbon dioxide, and other gases

– Moderate temperatures between day and night– Because of the greenhouse effect, the atmosphere

absorbs energy radiated by the Sun– Ozone: protects us from harmful ultraviolet radiation

and high-energy particles from the Sun– Burns-up small rocks and artificial satellites as they

enter our atmosphere– Original atmosphere was not like today (no oxygen)

The Inner and Outer Planets• Mars: Mars is the fourth planet from the sun. Befitting the

red planet’s bloody color, the Romans named it after their god of war. – Polar ice caps made of frozen carbon dioxide and may contain

small amounts of water– Terrain features indicate that water might have flowed across the

surface– Very thin atmosphere composed mostly of carbon dioxide– Has two small satellites (Phobos and Deimos)– Rotation (spin): 24.7 Earth hours– Orbit: 1.9 Earth years– Surface temperatures range from 144K to 300K


• Mars:– Mountain 3x larger than Everest– Many impact craters since thin atmosphere can

not burn up objects from space– Surface is red from iron oxide in its soil– Frequent dust storms


• Between Mars and Jupiter lie hundreds of smaller, rocky objects that range in diameter from 3km to 1,000km– These objects are called asteroids (smaller solar

bodies)• Some wander away from this region and may cross

Earth’s orbit


http://www.todayifoundout.com/wp-content/uploads/2011/12/Asteroid_Field.jpg

http://eps.utk.edu/research/images/asteroids.jpg

Asteroid Bennu

The Inner and Outer Planets• The Gas Giants: The outer planets are much larger

than the inner planets and have thick, gaseous atmospheres, many satellites, and rings– No solid surface– All the gas giants have rings– All have satellites: most cratered and some have thin

atmospheres• Jupiter: more than 60• Saturn: more than 40• Uranus: 27• Neptune: 13

The Inner and Outer Planets• Jupiter: fifth planet from the Sun

– The largest planet in the Solar System• 1,300 times the size of Earth

– First planet beyond the asteroid belt– Rotation (spin): 10 earth hours– Orbit: 12 Earth years– Atmosphere of swirling clouds of hydrogen, helium, methane, and

ammonia– Enormous storms: the Great Red Spot is a huge hurricane twice the

diameter of Earth• It has existed for hundreds of years

– The colorful bands of Jupiter are arranged in dark belts and light zones created by strong east-west winds in the planet's upper atmosphere traveling more than 400 mph (640 kph). The white clouds in the zones are made of crystals of frozen ammonia, while darker clouds of other chemicals are found in the belts.


• Saturn: Saturn is the sixth planet from the sun and the second largest planet in the Solar System– Considered to be still growing– Most extensive ring system

• Narrow bands of tiny particles of dust, rock, and ice ranging in size from a few millimeters to several meters

• Not known how they formed – 95 times the mass of Earth– Rotation (spin): a day is 10.7 hours– Orbit: 29 Earth years


• Uranus: Seventh Planet in the Solar system – Gaseous atmosphere composed of hydrogen, helium,

and methane (giving the planet a bluish color)– Rotation (spin): 17.25 hours– Orbit: 84 years– Atmosphere very cold (58K)

• Wind: 200 to 700 km/h– Most extreme tilt: 980 causing extreme seasonal

changes– Atmosphere very cold (58K)


• Neptune: Eighth and most distant planet from the sun – Gaseous atmosphere composed of hydrogen,

helium, and methane (giving the planet a bluish color)

– Rotation (spin): 16 hours– Orbit: 165 years– Storm systems may have winds up to 1,100

km/h

The Inner and Outer Planets• Beyond the Gas Giants are numerous small bodies composed of ice

and rock– One of the larger bodies is Pluto

• Was considered to be a planet up to 2006• The definition of planet set in 2006 by the International Astronomical

Union (IAU) states that, in the Solar System, a planet is a celestial body which:

• 1. Is in orbit around the Sun • 2. Has sufficient mass to assume hydrostatic equilibrium (a nearly

round shape) • 3. Has not cleared the area around its orbital path of debris.• A non-satellite body fulfilling only the first two of these criteria is

classified as a “dwarf planet“. (PLUTO)


• Pluto: dwarf planet– 0.002 Earth’s mass– Orbit: 248 years– Atmosphere: thin, gaseous and a solid, icy

surface


• Beyond Neptune lies the Kulper Belt– Region populated by many small bodies made

of ice and rock, including Pluto• Recently discovered another dwarf planet the size of

Pluto: Eris– Region still being explored

Formation of the Solar System• Early Astronomy:• Aristotle: The first model put Earth at the of the

Solar System• Copernicus (1543): Sun at the center and the

planets orbit in perfect circles• Kepler (1605): orbits around the Sun are ellipses

(ovals) rather than circles• Newton (1687): explained that gravity keeps the

planets in orbit around the Sun and satellites in orbit around the planets

Formation of the Solar System

• Nebular Hypothesis: – From their dating of rocks, scientist estimate

that the Solar System is approximately 4.6 billion years old

– Nebula: is a large cloud of dust and gas in space– Explains why objects that form from a disk will

lie in the same plane, have almost circular orbits, and orbit in the same direction

Formation of the Solar System• Nebular Hypothesis:

– The Sun, like every star, formed from a cloud of gas and dust that collapsed because of gravity

• In our Solar System, this process began almost 5 billion years ago

– As the cloud collapsed, it formed into a rotating disk. In the center, where the material became denser and hotter, a star began to form. As the cloud continued to collapse, it spun faster and faster.

– The spinning motion of the disk caused it to flatten. Planetesimals, or particles that became planets, began to form in the disk. Their formation caused more changes in the disk.


• Nebular Hypothesis:– As the planetesimals grew, their gravitational pull increased. The

largest planetesimals began to collect more of the gas and dust of the nebula

– Some planetesimals collided with large ones, and the planets began to grow larger and more stable. The warmer, inner planets were rocky, and the colder, outer planets accumulated lightweight gases in their atmosphere

– Because each planet swept up the material in its region, the planetary orbits are separate from each other. Asteroids and other small rocks are most likely leftover debris from solar system formation

Formation of the Solar System• Nebular Hypothesis:

– States that planets formed mostly through the process by which small particles collide and stick together, called accretion

– Explains why the terrestrial planets are different in composition from the gas giants

• Warm temperatures near the sun prevented light gases from remaining in the atmospheres of the terrestrial planets

• Colder gas and dust in the outer part of the disk became the gas giants– These planets were large enough and cold enough to hold light nebular

gases, such as hydrogen, in their atmosphere• Satellites may have formed around gas giants through the

process of accretion or particles captured by gravitational pull of gas giants


• Rocks in space:– There are many types of small bodies in our solar

system, including satellites, comets, asteroids, and meteoroids

• Satellites orbit planets• Comets are probably composed of material left over from the

formation of the Solar System• Most Asteroids can be found between Mars and Jupiter• Most Meteoroids that strike Earth burn up in the atmosphere

– Those that do not completely burn up in the atmosphere and hit the ground are called meteorites

Formation of the Solar System• Comets: a small body of ice, rock, and cosmic dust that follows an

elliptical orbit and that gives off gas and dust in the form of a tail as it passes close to the Sun– Composed of dust and of ice made from methane, ammonia,

carbon dioxide, silicon, magnesium, iron, and water• Because of their chemical composition they are sometimes

referred to ma dirty snowballs– Have long tails and icy centers

• When it passes near the Sun, it gives off gases in the form of a long tail of gases

• Tail brightens when it passes the Sun


• Comet formation:– During the formation of our Solar System, some small

planetesimals did not combine with other planetesimals. These leftovers strayed far from the Sun and developed very long orbital periods.

• Oort Cloud and Kuiper Belt• Most Comets are small bodies of rock and covered by ice

– Halley’s comet is one of the most famous. It travels in a highly elliptical orbit and appears in earth’s sky every 76 years

Halley’s comet travels in a highly elliptical orbit that takes it out into the Kuiper Belt


• Meteorites: three major types– Stony: include carbon-rich specimens that

contain organic materials and water• Greatest variety• Have compositions like Earth and Moon

– Metallic: made of iron and nickel– Stony-iron: are a combination of the two


• Meteoroids: most were once part of asteroids– a few came from Mars

or from our Moon


• Moon:– Its composition was found to be similar to Earth’s but

not identical• Therefore, the current theory is that the moon resulted from a

collision between Earth and another large body

– The giant impact hypothesis, sometimes called the Big Splash, states that the Moon was formed out of the debris left over from an indirect collision between the Earth and an astronomical body the size of Mars, approximately 4.5 billion years ago


http://en.wikipedia.org/wiki/File:Artist%27s_concept_of_collision_at_HD_172555.jpg


• Do other Stars have planets?– An exoplanet is a planetlike body that orbits a

star other than the Sun• Astronomers have discovered more than 200

exoplanets by measuring the small gravitational effects that they have on their parent Stars

chapter 19 the solar system. sun, earth, and moon the position of objects in the sky change over...

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