Solar System

Chapter 16

Times

• What makes one day?– The rotation of the Earth on its axis

• What makes one year?– The time the Earth takes to go one time

around the sun– 365 days, 5 hr, 48 min, and 46 sec

• Our present calendar is off one year in 128– So century years not divisible by 400 are not

leap years

The planetsA 50 point question on the final

• You will be asked to list the planets in the correct order and to write something about each of them.

• My Very Ernest Mother Just Served Us Nine Pizzas – Worth 50 points on the final exam

A model of the solar systemPlanet Size (diameter) Distance from sun

Sun 1.0 m

Mercury 0.7 cm 83.8 m

Venus 1.7 cm 154 m

Earth 1.7 cm 214 m

Mars 1.0 cm 325 m

Jupiter 20 cm 1,113 m

Saturn 17 cm 2,050 m

Uranus 7 cm 4,109 m

Neptune 7 cm 6,441 m

Pluto 0.3 cm 8,432 m

Solar system• Rocky planets

– Mercury– Venus– Earth– Mars

• Asteroids• Gaseous planets

– Jupiter– Saturn– Uranus– Neptune– (Pluto)– The gaseous may be so cold their surfaces are solid

or liquid.

Changes in Astronomy

• Objects as large as Pluto that are orbiting the sun have recently been discovered.– They have satellites (moons)

• There is no consensus on whether to call them “planets”– This year the International Union of

Astronomers voted to call Pluto and other similar objects dwarf planets

Mercury

Mercury• 88 days = one revolution around the sun (year)• 59 days = one revolution about its axis (day)

– Sun’s gravity locks density irregularities. Only rotates because of other planets (Venus)

• Radius = 1/3 that of earth• Mass is 1/20 of earth• Gravity = .38 that of earth• Very little atmosphere

– The planet is too small and too close to the sun for gravity to hold the gases of an atmosphere.

Mercury

• Daytime temperatures = 425 C

• Night = - 180 C

• Surface looks like the moon - marked by many craters.

• May never have been molten, so how did heavy material get to its center?

• Always appears close to sun (We can only see it close to sunset and sunrise.)

Venus

These pictures of Venus were taken April 14, 2006 by the European space prove. Future pictures will show 100 times as much detail. The colors are false to emphasize the winds around the south pole. There is an unusual cloud formation at the top of the day side.

Venus

• Once Considered our sister planet– In mass and size, closest to the earth

• Radius = that of earth

• Mass = .82 that of earth

• Gravity = 0.9 that of earth

• We would expect plate tectonics also on Venus but do, continents occupy 5% of surface area vs. 30% on earth.

Venus

• Brightest object in the sky - after the sun and moon - - can be seen in daytime also a morning star and evening star.

• When seen through the telescope has phases like the moon.

• 225 days to travel around the sun (year)

• 243 days to revolve once about its own axis (day)– Day is longer than its year (spins backwards)

Venus• Venus is the only planet that spins backwards on

its axis, probably due to earth's gravitational attraction.– The strong gravity of the sun would “lock” the planet

and keep it from rotating were the Earth not here.• Atmosphere is mostly CO2 (96%), some water,

nitrogen, oxygen.• Thick clouds made of sulfuric acid drops, very

strong winds, pressure 90 times that of earth• average temperature is 400º C. May have had

an atmosphere like that of earth at one time and a run-away green house effect taken over.

• No life possible now, maybe in the past.• In April 2006 a probe from the European Space

Agency began a study of Venus which should give valuable information.

Earth

Earth• Defines the ecliptic • Once was molten• Plate tectonics• First planet with a satellite (moon)• Green house effect makes life possible

– Adds +35 degrees C to the average temperature

• Almost a sphere– 43 km in 6400 km– Columbus was way off in the radius– Radius had been determined by the Greeks

before Christ

EarthSun can be straight overhead between the

tropics of Cancer and Capricorn

At some times the sun never rises or sets between the Arctic circle and the Antarctic circle

Moon

• Four theories of formation– Formed at the same time as Earth– Formed elsewhere and was captured by Earth– Split off the Earth

• Accounts for the thin crust over the oceans

– A large asteroid hit the Earth causing part of it to break off

• Present moon contains material from the asteroid and the Earth

• Most accepted theory at the present time

• Because of gravitational friction, the moon is moving away from the Earth a few inches a year

Moon’s phases• Moon reflects light from the sun

– It has no light of its own– We can only see the part of the moon the sun

lights– When the moon is closer to the sun than the

Earth, we see less than half– When the moon is further from the sun than

the Earth we see more than half.

• The moon is in the sky as much in the day as it is at night.

These pictures of Venus were taken April 14, 2006 by the European space probe. Future pictures will show 100 times as much detail. The colors are false to emphasize the winds around the south pole. There is an unusual cloud formation at the top of the day side.

DayNight

Mars

Crisp details in a suite of mid-latitude gullies on a crater wall are captured in this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) view obtained in southern winter on 12 October 2006. During southern winter, shadows are more pronounced and the atmosphere is typically quite clear. These gullies, which may have formed in relatively recent martian history by erosion caused by flowing, liquid water, are located in a crater on the east rim of Newton Crater near 40.4°S, 155.3°W. Sunlight illuminates the scene from the upper left. The picture covers an area about 3 km (1.9 mi) wide; the crater rim is on the right side of the image, the crater floor is on the left. North is toward the top/upper left.

Mars Global Surveyor (MGS) view obtained in southern winter on 12 October 2006. These gullies may have formed in relatively recent martian history by erosion caused by flowing, liquid water. The picture covers an area about 3 km (1.9 mi) wide

Mars

• Second brightest planet• Reddish in color• Diameter half that of earth• 11% earth's mass• Gravity = 38% that of earth• Day = ~24 hours• Year = ~2 earth years• Average temperature = - 30 ° C, 20°C is hottest,

-70 ° C is coldest• No Ozone to screen UV rays.• Once was water, none is on the surface now

Mars

• Not enough internal heat to drive tectonic processes

• Surface has many interesting features including what appear to be water channels.

• May have been life at one time, none now

• Atmosphere, mostly Carbon dioxide (95%) (1% density of earth's atmosphere)

• Two very small moons.

Manned mission to Mars

• President Bush has told NASA to plan for a manned mission to Mars as soon as practicable. There is considerable discussion about the expenditure the funds necessary for such a project.

• One problem is that the astronauts will receive a very large dose of radiation during the mission, both while on the way and while on Mars.

• The Earth’s magnetic field protects us from this radiation.

Mars surface

Clay, such as that shown as red in this picture indicate that water existed on Mars for a time long enough for life to develop. We have no indication yet that life did develop. April, 2006.

Search for life on Mars• Many scientists

believe that if water existed for a sufficiently long time on Mars, we should find fossils of some types of life

• We will see.• My own personal

opinion is that life doesn't happen so easily

There are currently two probes on the surface of Mars sending back pictures.

Scientific American December, 2006

Scientific American December, 2006

Scientific American December, 2006

Scientific American December, 2006

Asteroids

Asteroids• Most lie between Mars and Jupiter• Rocks in space, largest (diameter = 1000

km) size of state of Texas• Some have orbits that cross the Earth’s

orbit• Similar in composition to stony and stony-

iron meteorites • This last year, a probe landed on a

meteorite• In 2005 an unsuccessful attempt was

made by a Japanese probe to land on an asteroid and return to earth with samples.

Jupiter

Jupiter

• Volume is 1300 times that of earth

• Mass is 318 times that of Earth

• Spins so fast it is fatter at the equator

• Made of mostly hydrogen and helium– As are the rest of the gaseous planets– And the rest of the universe

• Has a permanent storm (great red spot)

• Very hot core is metallic hydrogen (not sure if solid or liquid)

Jupiter

• Number of very interesting moons – at least 16– largest is size of planet Mercury– third is size of our moon– some are very small– One has active volcanoes– another is covered with ice, best possibility for

extraterrestrial life in the solar system

• Has a very strong magnetic field, 10 times stronger than earth. May be due to metallic hydrogen.

Jupiter

• Probe that went into atmosphere in April 1996, showed smaller amount of water than anticipated

• Still cooling off, it is radiating more energy than it is receiving from the sun

• Some details about Jupiter’s interior were revealed when a comet collided with it. The most important thing is that the models did not predict the observed results. We don’t understand much about these large gaseous planets.

Cracks on Europa's Surface

The cracks are ice on an ocean of water.

IO – A moon of Jupiter had the largest volcanic eruption ever seen anyplace. Happened in 2001, covered more than a 1000 square miles. Earlier in its history Earth may have had such eruptions.

-This is the only body other than Earth to have volcanoes like Earth with lava about 1300º C.

Saturn

Saturn (taken from Chile)

SaturnThe image, acquired by Cassini’s visual and infrared mapping spectrometer, shows Saturn lit by its own internal, thermal glow. Clearly visible is a 60,000-kilometer-long (37,000 miles) string of bright “pearls,” which are actually clearings in Saturn’s deep cloud system. More than two dozen cloud clearings appear at Saturn's north latitude. Each clearing follows another at a regular spacing of about 3.5 degrees in longitude. This is the first time such a regular and extensive train of cloud clearings has been observed, indicating that they may be a result of a large planetary cloud formation or wave that might encircle the whole planet.

Hyperion

In 2005 Cassini flew by Hyperion at a distance of 310 miles (500 kilometers). Hyperion is 163 miles (266 kilometers) wide. It has an irregular shape, and spins in a chaotic rotation. Much of its interior is empty space; it’s like a pile of rubble, scientists say.

Tethys

The new images suggest the possibility that Hyperion’s crater walls have experienced multiple episodes of landslides. Such "downslope" movement is evident in the filling of craters with debris and the near elimination of many craters along the steeper slopes.

Photos by Cassini.

Saturn

• Many large beautiful rings• Made of hydrogen and helium• Much like Jupiter only colder (-180 °C) and a

little smaller• Has 23 known moons

– Titan, has an atmosphere (only moon to do so)

• Roche Limit - closest that a moon can be and not break up due to gravitational forces– 2.4 times the planet's radius

• Rings are chunks of rock and ice from size of buildings to dust.

Huygens' First Image of Titan

Titan is a moon of Saturn, ten time further from the sun than Earth.

The Atmosphere is hydrocarbons.

Temperature is -323º F

Methane is a liquid and rains and flows in rivers.

The parachute took 2.5 hours to lower the probe to fall through the dense atmosphere.

Nasa – Dec. 2005

The largest “rock” in the picture is 6” across and may be ice.

Enceladus spews ice.

A mysterious energy source is heating up the southern pole of Saturn's moon Enceladus, triggering blasts of highly pressurized water ice that is spewing hundreds of miles into space, say scientists who this week released pictures of the fountains taken by the Cassini satellite.

Dec.12, 2005

Mars Global Surveyor (MGS) view obtained in southern winter on 12 October 2006. These gullies may have formed in relatively recent martian history by erosion caused by flowing, liquid water. The picture covers an area about 3 km (1.9 mi) wide

Uranus

Uranus

• Diameter 4 times that of earth

• Colder than - 200°C

• Mostly hydrogen and helium

• Spins only 8 degrees from its side perhaps due to collision with an earth sized object early in its history

Neptune

Neptune

• Diameter 4 times that of earth• Colder than - 200°C• Atmosphere more stormy than

Uranus (We don't know why)• Great dark spot (high methane

clouds)

Pluto – Best pictures ever taken(by Hubble). Done in 1996

Pluto – now a dwarf planet

• Very cold, very small (two-thirds size of our moon), very difficult to obtain data about.

• Has one moon, half as big as Pluto itself, circles the planet every 3.2 days (earth's moon takes 28 days).

• First pictures showing any detail were taken in 1996 by Hubble. All that can be said is that there are dark areas and light areas. 

• A probe launched in 2006 that will give us much more information but it will be several years before it arrives.

Sedna• First seen by

astronomers using California's Palomar Observatory, and has been given the name " Sedna" after the Inuit goddess of the ocean.

• Slightly larger than Pluto

• 3 times further from sun

• Called a dwarf planet

BBC World News figure

Comets

Comets• Very elliptical orbits

• As they get close to the sun dust and water vapor is driven off the "snow ball", this reflects light and causes the comet's tail.

• When the Earth goes through such a tail we get a meteor shower.

• A comet may have been the cause of the large explosion in Siberia.

Inside a comet

Picture taken of the nucleus of a comet by the Stardust probe.

The probe returned the samples taken from the tail of the comet this summer.

The Aurora from the space shuttle

The Aurora in Wisconsin

Aurora

• Northern Lights• Caused when charged particles from

the sun interact with the earth's magnetic field