Midterm 2 Flashcards
1
Q
How many planets are in our solar system?
A
8
2
Q
Where did the leftover material go?
A
Small solar system bodies, asteroids, comets, Trans-Neptunian objects
-Flew around solar system crashing into planets and moons forming craters
3
Q
Terrestrial planets
A
The group of planets that includes the first four planets from the Sun
-the inner 4 planets
4
Q
Jovian planets
A
The group of planets including Jupiter, Saturn, Uranus and Neptune
-second 4 planets
5
Q
Average density
A
The total mass of a planet divided by its total volume
6
Q
Albedo
A
The percentage of sunlight that is reflected from a celestial object
-percentage of sun light reflected by a planet or moon
7
Q
Astronomical Unit
A
The average distance from the Sun to the Earth
8
Q
Which planet has the highest average density?
A
Earth
- Terrestrial planets are much more dense than the Jovian
- Mercury has smallest diameter
9
Q
Solar Nebula
A
The rotating disk of gas and dust out of which the solar system was formed
10
Q
Formation of the Solar System
A
Began with Solar nebula (cloud of gas and dust) which began to contract
- very cold, 100 A.U., rotation
- Nebula contracts and rotates forming a flat rapidly rotating disk - the central concentration becomes the protosun
- protosun became very hot, ice was vaporized and light elements pushed to outer part of disk - heavier elements left in the inner solar system
- little dust grains, pebbles, and other materials began to bump into each other and stick together
- over a few million years these formed objects about 100 km in diameter called planetesimals
11
Q
Planetesimals
A
During the formation of the solar system these objects were the first to form from sticking together (100 km in diameter)
12
Q
T/F - In order for the formation to begin the solar nebula had to be very hot
A
FALSE
-think about boiling water. It expands. we need contraction for formation to begin
13
Q
Where is there evidence of disks that might form solar systems around stars
A
In the Orion Nebula
14
Q
T/F - We have found at least 5 solar systems that look exactly like our solar system
A
FALSE
15
Q
Protoplanets
A
Formed as the planetisimals collided after 50 million years
- began with 100 planetisimals orbiting the sun
- after 30 million years, 100 turned into 22 planetisimals
- after 441 million years, four planets remain
Protoplanets cleaned up the material in their orbits to become PLANETS after 100 million years
16
Q
formation of planets
A
First the terrestrial planets formed by collisions and accretion of planetisimals
- the Jovian planets formed by gas accretion
- last, the Jovian planets likely have moved a bit from where they were formed
17
Q
Finding planets
A
- Radial velocity shifts
- brightness changes from a planet crossing in front of the parent star (transiting planet)
- microlensing
- direct imaging
Kepler satellite currently finds extrasolar planets using transiting planet method 2
18
Q
Radial Velocity shifts
A
(Doppler effect)
- planet causes the star to shift just a little bit, but that shifts the spectral lines
- moving toward the earth causes a “blue shift” and away is “red shift”
19
Q
Planetary transits
A
- When a planet transits (moves in front of) a star, it blacks out part of the star’s visible light (amount of dimming tells us the planets diameter)
- when planet transits the star, some light from the star passes through the planet’s atmosphere on its way to us (reveals composition of stars atmosphere)
- when planet moves behind the star, the infrared glow from the planet’s surface is blocked from our view (amount of infrared dimming tells us planet’s surface temp.)
Used in Kepler mission
New planets outside our solar system
-Kepler 7b, Kepler 5b, Kepler 8b, Kepler 6b, Jupiter, Kepler 4b. earth
-mostly very warm, 2000 F and above
20
Q
Microlensing
A
One method for finding planets outside our solar system is microlensing, which occurs when a star passes in front of another star. The gravitational field of the passing star causes a gravitational lens to form which brightens the background star’s light. If a planet is orbiting the front star, it will also gravitationally lens the background star, just at a smaller magnitude. This amount of light given off from the background star indicates the presence of an extra-solar planet.
21
Q
Direct imaging of Extra-solar planets
A
With modern detectors there have been a couple cases where planets have been directly imaged by blocking the light of the star
22
Q
What makes the Earth Unique?
A
Only place with life so far
- the atmosphere (77% Nitrogen, then oxygen, almost zero CO2 - protection from UV radiation, 1 Atm of pressure) (Venus 96% CO2, Almost zero oxygen and 4% nitrogen - 98 Atm of pressure)
- magnetic field
- plate tectonics
- oceans of liquid water (maybe not unique any more)
23
Q
Earth atmosphere
A
- Sunlight arrives at the earth
- 39% of sunlight is reflected by clouds and the surface
- Sunlight that is not reflected is absorbed by surface, heating it.
- heated surface emits infrared radiation
- Some infrared radiation is trapped by atmosphere, heating both atmosphere and surface
- Remaining infrared radiation “leaks” into space
24
Q
Earth’s magnetic field
A
Iron core, fast rotation, dynamo effect
- helps protect us from charged particles in solar wind
- van allen radiation belts
- Aurora Borealis
25
Aurora Borealis (what feature in the sky contributes to these events?)
Caused by charged particles entering the atmosphere near the poles of the earth
- happens after solar flares
- color depends on type of molecule activated
- rare in Utah, easier to see in Eastern U.S.
What feature in the sky contributes to these events?
-Earth's magnetic field
26
Earth's plate tectonics
Earth made up of many plates - plates slide
- mid ocean rifts
- --mid-Atlantic - Atlantic getting bigger and Pacific getting smaller
- active regions on earth
Pangea - supercontinent 237 million years ago - broke up
- plates have been moving a long time
- continents were different in the past
27
Rocks
Rocks tell us a lot about the nature of earth (and moon)
- Pure elements (sulfur, carbon, gold)
- minerals
- Types of Rocks
1. Igneous (Basalt)
2. Sedimentary (limestone and sandstone)
3. Metamorphic (marble)
28
Igneous rocks
Solidified from molten state like lava
| -often related to volcanoes
29
Sedimentary rocks
Produced layer by layer
| -formed by wind, water and ice
30
Metamorphic rocks
Take one of the other types and put it under pressure and high temp.
31
Seismic waves
P-waves (primary waves)
- compression waves
- these travel fastest
- can travel through liquid
S-waves (secondary waves)
- transverse waves
- cannot travel through liquid
- provided evidence of structure of earth
32
Earth compared to moon - internal structures
Earth
- solid iron core
- liquid iron outer core
- mantle
- crust
Moon
- possible iron core
- non-rigid inner mantle
- solid upper mantle
- crust
- there is some newer evidence that the core might be molten
- due to differentiation, iron sank to the center and less dense material floated upward
33
Origin of the earth moon system
| -fission theory
Proto-earth rotating rapidly
- moon pulled out of earth
- doesn't explain moon's lack of dense elements
34
Origin of earth moon system
| -capture theory
Moon formed elsewhere
| -then capture by earth
35
Origin of earth moon system
| -co creation theory
Formed near each other
| -doesn't explain lack of dense elements
36
Collision-Ejection theory
- currently the most accept theory
- earth hit by a mars size object
- then material reformed into earth and moon
- impact also believed to speed up earth's rotation and cause its tilt
- earth reformed as a largely molten body and moon aggregated from the debris
- ancient moon rocks brought from Apollo causes astronauts to support this theory
37
Features on the moon
Two main regions on moon
- Maria (sea)
- Lunar highlands
Both are then covered by craters
-rocks tell us a lot about the nature of the moon
38
What did Astronauts find on the moon
Maria (Sea - 17% of surface)
- dark areas on the moon
- found to be lava flows
- rocks from these regions were Basalt like those found in Hawaii or Iceland
- Mare basalt
- --show small crystals - this implies that the cooling of lava was very fast
- heavy elements (iron, manganese)
- cracks in Maria called Rilles
39
What did Astronauts find on moon 2
Highlands (83% of surface)
- light colored rocks
- Anorthosite
- --found only in old mountains on earth
- --lighter elements rich in calcium and aluminum
- long crystals meaning slow cooling time
- often fractured from impacts
- studied by later Apollo missions - first by apollo 15
This was critical discovery in support of the collision-ejection theory
40
Other things astronauts found on moon
Regolith
- "blanket of stone"
- find powder and rock fragments (covers surface)
- from meteoritic bombardment
impact breccias
- fused rock
- from impact sights
- can show mixed of other types of lunar rocks
41
Theory of cratering and maria
- first 800 million years dominated by frequent impacts causing highland craters
- near the end of this time a number of large impacts created the Maria
- --impact melted the maria basins - this is lava flow
- later cratering in Maria and Highlands
42
Water on the moon?
up until 1994 people said NO!
- 1994 CLEMENTINE observed moon and found evidence for a patch of water at the moon's south pole (10-100km across)
- being disputed again, maybe it isn't the form of water
1998 Lunar prospector arrived at moon and confirmed previous observation and found more evidence at north pole
- data suggests ice at poles
- may have been deposited by comets
- much debate on this
43
Terrestrial planets
Orbital length - mercury, venus, earth, mars
rotation period - earth, mars, mercury, venus
solar day - earth, mars, venus, mercury
diameter - mercury, mars, venus, earth
Mars is least dense, earth is most
Earth has most gravity, then venus, then mercury and mars tied
44
Caloris Basin
One of Mercury's largest features
- very violent event
- remnant of large impact that penetrated the crust
- CAUSED BY AN IMPACT FROM AN EXTERNAL OBJECT
Opposite side from calories basin
- unusual hilly terrain
- seismic waves from calories impact traveled through planet
45
Mercury features
surface is generally rolling plains with long cliffs called scarps
-too small and too close to sun to have an atmosphere
Average density is almost equal to earth (both have iron cores)
-core is 42% of planet's volume
-large iron core
MESSENGER found larger magnetic field
-only other rocky planet with global magnetic field
-however, planet is so small the center should have solidified already
46
Slow rotation of Mercury
-Mercury is almost tidal locked to the sun like the moon is to the earth (but 3-2 instead of 1-1)
Slow rotation causes
-temp. of surface facing sun is 700K (800 F)
-dark side is 100 K (-280 F)
-temp range is 1080 F
-earth rang is 20 F
-LARGE TEMP RANGE BTWN SIDES FACING SUN
47
MESSENGER
Currently on its year long science orbits
- we continue to get new data on Mercury
- this is one to keep an eye on as we learn a lot of new things about this little planet
- there is even some evidence of water at poles but that would be very surprising
48
Venus observations
- very thick atmosphere we can't see through
- ---96% CO2
- ---4% Nitrogen
- ---sulfur dust, sulfur dioxide, hydrogen sulfide
- ---yellowish, orange clouds (clouds of concentrated sulfuric acid)
- ---Troposphere, stratosphere, mesosphere (majority)
- --most efficient greenhouse gas effect in solar system
- temp. 900 F (temp. almost constant over entire surface of venus - pressure 98 atm)
- surface contained lava rocks
- basalt rocks similar to ones found on earth and moon
49
Spacecraft to Venus
U.S. Probes
- MAGELLAN (1990)
- --crashed into atmosphere after mission
- --used Radar Echo Ranging to peer through the clouds
50
Surface of Venus
80% volcanic plains and rolling hills
2 main continents
-Ishtar Terra (Australia)
-Aphrodite Terra (Africa)
High point is Maxwell Mons (coolest and lowest pressure spot on Venus)
-debate on how many feature were formed on venus
51
Active surface of Venus
much of the change comes from rapid convection currents under the surface - leads to very thin crust (much thinner than earth's) - surface breaks up into crumbles - mantle spits out blobs of hot lava to form mountains and volcanoes
-no real plate tectonics
no magnetic field - if there is it is very weak
52
Mission to the moon
Challenge put forward by JFK 1960s - to put man on moon and return him safely to earth
-Apollo 11 1969
Only 12 MEN have walked on the moon
53
What evidence to scientists have of the collision-ejection theory?
The moon is made of less dense material than the earth
54
What is the most abundant element in the earth's atmosphere?
NITROGEN
55
T/F - There is no evidence of water on the moon?
FALSE
56
Who has the longest solar day of the terrestrial planets?
MERCURY
57
What do we not found in Venus Atmosphere
OXYGEN
58
Spacecraft missions
Venus
- Magellan
- Venera 13
Moon
- Clementine
- Apollo
Mercury
-Messenger
59
Why is it important to understand rocks found on earth as we study the solar system?
It is important to understand rocks and their purpose and effect on earth so we can compare them to the rocks found on other planets or objects in the solar system. By looking at the rocks use and characteristics, scientists can infer the properties of other planets in comparison and also make theories of their origins. For example, igneous rocks found on another planet could indicate volcanic activity.
60
From the rocks astronauts brought back from the moon we find short/long crystals. What does this tell us?
The rocks with short crystals provide evidence of lava flows in which the lava cooled very quickly. The rocks with long crystals mean there was a slow cooling time in this area on the Moon.
61
What is the only planet whose surface features can be seen from earth?
Mars
62
Christian Huygens
1659 - first reliable observations
- observed feature to repeat on a period of about 24 hours - predicted period of rotation
- similar to earth so martian stories began
- Giovanni Schiaparelli saw CANALI (Water channels) crisscrossing lines on surface
- Flagstaff AZ observatory sa 160 canals and thought it was irrigation system
Canals were not seen in close-ups of Mars
- cratered like moon - saw signs of erosion in craters (Mariner spacecrafts)
- duststorm
63
Mariner 9 on mars
Found 4 geological areas
- volcanic (most surprising discovery)
- canyon areas
- expanses of craters
- terraced areas near poles
64
Volcanic regions on Mars
contained in N Hemisphere
- largest volcano is OLYMPUS MONS
- ---area as big as Missouri
- ---collapsed Caldera at the summit as large as the entire Hawaiian island chain
- three other volcanoes in this region (Tharsis rise)
65
Canyon areas of Mars
Btwn the 2 hemispheres
-parallels the equator
-VALLES MARINARIS
(on earth it would run from NY to LA (3000 KM))
----not formed from erosion like grand canyon
----might have formed by early plate tectonics on Mars (6 km deep and 190 km across)
66
Polar regions on Mars
Water may have once flowed on Mars
- there really are water channels on Mars (very ancient)
- some water still in Polar Ice caps - some possible permafrost (large amounts of CO2 ice (dry ice))
67
Water on Mars
Found a number of things that point to a sea on Mars
- one is Moqui Marbles (hermatite concentrations)
- ---only found when there has been water
- ---called them blueberries when they saw them
- ---minerals precipitate from flowing ground water - once dried up the erosion exposes the "marbles" - you could find earthly variety in local rock shops
- ---on earth in Southern Utah
- regions like beaches where the water made ripples in the sand that then hardened
68
Mars atmosphere
Started out similar to Earth's
- current: 3% nitrogen, no oxygen, 95% CO2, 2% other (Argon)
- very thin - pressure .007 atm
- very inefficient Greenhouse effect
- temp. (-67 F)
- large dust storms
69
Missions to Mars
```
Viking 1 (July 1976-Nov 1982)
Viking II (Aug 1976-Apr 1980)
```
70
Moons on Mars
2 MOONS
- Phobos (Fear) and Deimos (panic)
- named after horses that draw Mars Chariot
- look like 2 asteroids
- orbit over the equator
- both tidal locked to Mars
71
Phobos
Larger moon of Mars
- orbits in 7h 39m
- will cross the sky in 5.5 hours
- orbits at 6000 km (Earth's moon is at 376,280 km)
72
Deimos
Smaller moon on Mars
- orbits at 20,000 km
- almost in a synchronous orbit
73
Jovian Worlds facts
GAS GIANTS
Jupiter rotates fastest and is largest in mass and diameter
-all less dense than terrestrial (saturn is least dense)
Composition
- all about 80-90% hydrogen
- then 10-20% helium
- methane
- ammonia (Jupiter and Saturn)
- water vapor (Jupiter and saturn)
74
Internal structure of Jupiter
Rocky core about 20,000 km in diameter
- surrounding core is a thick layer of liquid metallic hydrogen (40,000 to 50,000 km thick)
- Above this is outer layer composed of molecular hydrogen (10,000 to 20,000 km thick)
- bright cloud patterns are only the top 100 km of this last layer
Jupiter core is small and biggest area is 2 layer
75
Internal structure of Saturn
Similar to Jupiter
- Rocky Core (26% of mass in core, where only 4% for Jupiter)
- a thinner layer of liquid metallic hydrogen
- a large layer of molecular hydrogen
- clouds are in outer layer
- much thicker cloud layer in Saturn
Saturn core is larger than Jupiter (2 layer is smallest and 3 is biggest)
76
Internal structure of Uranus and Neptune
Rocky core about the size of the earth
- above this is a layer of frozen or liquid water
- ---contains ammonia - making the mantle similar to your average window cleaning fluid
- on top of this is a shallow layer of liquid hydrogen and helium
- not enough pressure to get metallic hydrogen
77
Visible cloud patterns
Belts and Zones
- Belts: sinking cooler material (Dark)
- zones: rising warmer material (light)
- these alternate over the surface
- rotate at different speeds - alternating directions
78
The Great red Spot
Jupiter - three earth's could fit side by side inside the storm
- giant hurricane
- counter-clockwise rotation
79
Jupiter's cloud patterns
White ovals
- similar but smaller than the great red spot
- seen in Jupiter's southern hemisphere
- counter clockwise flow
Brown ovals
- seen in N hemisphere
- thought to be holes in the upper atmosphere
- give us a view of deeper layers inside Jupiter
80
Galileo Spacecraft
Jupiter (1995)
- Galileo Probe dropped into the atmosphere
- spacecraft into orbit
81
Cassini Orbiter
planned 4 year mission to Saturn
- orbits Saturn and monitor its atmosphere and rings
- will make 40 flybys of Titan
- will radar map the surface and observe other moons
82
Voyager I and II
Eventually both explored all the giant planets
Voyager I took pictures of Jupiter
Voyager II was hoped to see cloud features on Uranus like seen in Jupiter and Saturn
- when it saw Uranus it had almost featureless clouds - this may have been due to the tip of the planet or the current season
- the axis of rotation is 98% from the plan of the solar system
- it rolls on its side
- when Voyager II encountered Uranus it's rotation axis pointed at the sun
- cloud bands have appeared since the axis points a different direction
83
Voyager II to Neptune
August 1989
- expected a repeat of Uranus but got a surprise
- saw bands, spots and other structure in Neptune's atmosphere
- last stop for Voyager II
- for both Uranus and Neptune the blue color is from Methane
84
Cloud features of Neptune
Great Dark spot
- HST saw spot fade
- reappeared in opposite hemisphere
Belts and zones
-less defined than Jupiter's
Wispy Cirrus clouds
-crystals of methane ice
85
What material makes up the majority of the Jovian worlds?
Hydrogen
86
The blue coloring of Uranus and Neptune comes from what?
Methane
87
Spacecrafts
Saturn
-Cassini Probe
Mars
-Viking spacecrafts (landers)
Jupiter
-hit by comet Shoemaker-Levy 9
88
What planet was featureless when first seen
Uranus
89
What planet is largest in terms of Radius
| -smallest of the blue gas giants?
Jupiter
| -Neptune
90
What planet laid on its side with respect to the plane of the solar system
Uranus
91
What are real features on the surface of Mars seen by MODERN spacecraft
- Volcano size of Missouri
- a massive canyon caused by ancient plate tectonics
- polar ice caps
- a thin atmosphere of mostly CO2
-NOT A SYSTEM OF CANALS IN MODERN CLOSE UPS
92
T/F Jupiter and Saturn are entirely gaseous with no solid surface
FALSE
93
T/F Seasons on Uranus would be more extreme than on earth
TRUE
94
T/F All the ice on Mars is in the form of water ice
FALSE
| -much of it is dry ice (CO2 ice)
95
Belts and Zones descriptions
The zones and belts on the Jovian worlds are visible cloud patterns that alternate over the planet's surface. Belts are a dark, sinking cooler material, where zones are a light, rising warmer material. Jupiter's are the most obvious, having a massive Great Red Spot, as well as several white ovals in the southern hemisphere and brown ovals in the northern hemisphere. Saturn also has prominent cloudy spots that can be observed. Uranus sometimes has featureless clouds, which can only be seen depending on which way it's axis is pointing. Neptune's bands and spots are less defined than Jupiter's, but it does have a faded Great Dark Spot.
96
William Herschel
Discovered Uranus 1781
- first thought it was a comet
- finally determined it to be a new planet at 19.2 A.U. (as predicted by Bode's law)
- named it Georgium Sidus (George's Star) after George III
- the name Uranus came decades later
However, Herschel was not the first to see Uranus
- it appeared on at least 20 star charts drawn btwn 1690 and 1781
- on a clear night it might be visible to the naked eye
- HERSCHEL WAS THE FIRST to track its motion relative to the stars
- didn't learn much about Uranus until the Voyager iI mission 1986
97
History of Neptune
Neptune was found by searching
-studies of Uranus showed slight deviations from predicted positions
JOHN COUCH ADAMS suggested another planet might cause the deviations and predicted to the position to be in Aquarius
URBAIN JEAN JOSEPH LE VERRIER (French astronomer) came to same conclusion and predicted a similar position
98
John Couch Adams
Suggested another planet might cause the deviations of Uranus and predicted to the position to be in Aquarius
- Adams told Astronomer Royal of Great britain and search made in summer 1846
- Adams position had large errors
99
Urbain Le Verrier
Le Verrier contacted Berlin Observatory Sept. 1846 and JOHANN GALLE found Neptune that very night after a half hour search
- Le Verrier suggested the name Neptune, but credit is given equally
- Also note Galileo may have seen Neptune in 1613 as an extra satellite of Jupiter
- it took Voyager II to get details
100
Magnetic Fields of Jupiter and Saturn
The metallic liquid hydrogen leads to a magnetic field
- Jupiter's is 19,000 times stronger than Earth's
- Saturn's is smaller than Jupiters
- Saturn's has no tip from rotation axis
101
Magnetic fields of Uranus and Neptune
- Stronger than Saturns
- 50 times stronger than Earth's field
- tipped 59 degrees from rotation axis
- magnetic field is off-center
- not a dipole field
- origin of field is unknown
- Neptune's tipped 47 degrees - very off center
102
History of Rings
1610 GALILEO was first to observe Saturn
-saw 2 lumps on opposite sides of planet - disappeared in 1612 and reappeared in 1613
CHRISTIAAN HUYGENS 1655 observed Saturn with much better telescope
- suggested that Saturn was surrounded by a thin flattened ring - disappearance due to tip of ring with respect to the Earth
- theory of how Saturn "loses its rings"
103
Giovanni Cassini
1675 identified a dark division in the ring
- now called the Cassini division
- separated the right into the A ring and B ring
1800s found C ring
-now have D, E, F, G rings and the Encke Division
A-E, OUTER TO INNER
- Cassini division btwn A and B
- Encke gap inside A
104
What are the rings
Ring particles
- ice or ice covered rocks (confirmed by Voyagers)
- max size 10 meters, min size 1 cm (average size of 10 cm (snowball)
- Follow Keplerian orbits!
105
Roche Limit
Some say the rings are just material which didn't form a moon
- THIS MATERIAL COULD NEVER FORM A MOON
- The tidal force from Saturn is stronger than the gravitational force btwn any 2 pieces of ring material
ROCHE LIMIT
- The point at which the tidal force exactly matches the Gravitational force
- therefore anything inside the Roche Limit cannot accrete material
- most of the rings of Saturn lie within the Roche limit (but there are objects inside the Roche limit)
- there are a number of SHEPHERD Moons that orbit on either side of the narrow rings to keep them tight
106
The rings
We find that the rings are actually made of many ringlets
107
Jupiter's rings
Faint set of tenuous rings
- around the equator of Jupiter
- made of rock (not ice like Saturn)
- small particles (.001 mm)
- reflect very little light
108
Rings of Uranus
Faint set of rings
- discovered by accident in 1977
- during an occultation of a distant star, the rings blocked the light before the occultation was to being
- these rings follow the equator of the planet
- small dark rings of 1 m diameter particles
- most rings less than 10 kmwide
109
Rings of Neptune
Just like Uranus
- faint, thin rings of dark material
- around the equator of the planet
- very hard to see
110
Jupiter's moons
```
63 total currently
4 Galilean Moons
-lo
-europa
-ganymede
-callisto
```
111
Lo
Densest of the Galilean moons
- orbit 1.769 days (3630 km)
- the most surprising moon of the Jupiter system encounter by the Voyager probes
- similar in size to the moon
- thought it would be geologically dead
Surprise at Lo
- volcanically active
- molten interior
- travels in a plasma torus of sulfer
112
Europa
Smallest Galilean (orbit 3.551 days)
- made famous in the 2001 series
- is a frozen world on the surface but may hold surprises below
- is dense enough that is should have solid materials below
- may have liquid oceans under its frozen surface
- ice is almost pure water ice
113
Ganymede
Largest Galilean - larger than moon and Mercury
- largest rocky surface of any moon
- orbit 7.155 days
- large icy world
- dark and cratered
114
Callisto
Larger than the moon - almost same size as Mercury
- orbit 16.689 (longest Galilean)
- furthest out of the Galilean moons
- least dense of the group
- like Ganymede it is dark and cratered
- another icy world
115
Moons of Saturn
```
61 total
Shepard moons
-Prometheus and Pandora
-orbit on opposite sides of the F ring
-they keep the ring confined
-they produce a well-defined narrow ring about 100 km wide
```
116
Keeler Gap
As Daphnis moon orbits, its gravity induces scalloping along the edges of the gap
- btwn outer edge of A ring
- creates Keeler gap
117
Mimas
Saturn
The death star
-smallest and innermost of 6 larger moons
-400 km
-impact site called Herschel is 130 km in diameter
118
Enceladus
Similar in size to Mimas (Saturn)
- most reflective object in the Solar system
- smoothed surface
- more reflective than freshly fallen snow
- surface is pure ice with little dirt or rock
- geologically active moon
- activity keeps surface smooth and reflective
- Cassini shot close up
119
Titan
Saturn
- early earth? - reminds one of Venus - can't see through the clouds
- Thick atmosphere (about 90% nitrogen, hydrocarbons, may have rivers and lakes of ethane)
- has all the building blocks of life
- atmosphere similar to early earth's
- however temp. is 95 K (-288 F)
- second in size to Ganymede for rocky surface
- largest moon if you count the atmosphere
120
Cassini Mission
To Saturn
- dropped the Huygens Probe
- dropped into the atmosphere of Titan
- this will further analyze the atmosphere
- 2.5 hour descent to the surface
- it survived the landing and reported on surface features
121
Saturn moon groups
Inuit Group (5 moons)
- prograde
- high inclination 45-50 degrees from rings
Gallic group (4 moons)
- prograde
- intermediate inclinations
Norse Group (29 moons)
- retrograde orbits
- majority are very small
- largest might be a captured Kuiper Belt Object (Phoebe)
122
Moons of Uranus
27 total (Shakespeare names)
- orbit around the equator of Uranus
- 10 of the moons discovered by Voyager II
Only 5 large moons
- Miranda
- Ariel
- Umbriel
- Titania
- Oberon
123
Miranda
The moon built by committee
- Miranda is the smallest of the large moons
- very strange features
124
Moons of Neptune
13
| -many named for Nereids or the sea nymphs - the 50 daughters of Nereus and Doris
125
Triton
Neptune
- Triton is the only large moon with a retrograde orbit
- only object to be thought to be captured into a retrograde orbit
- orbit tipped 23 degrees from equator of Neptune
- just a little smaller than the moon
- geologically active
126
Who discovered Uranus and what year?
William Hershel 1781
127
Which planet was discovered by predicting its position then looking for it?
Neptune
128
Which planets have rings?
Jupiter, Saturn, Uranus, Neptune
129
Describe Saturn's rings
Ice (ice covered rock) about 10 cm in size
130
T/F - There are no moons inside of Roche Limit in Saturn?
FALSE
| -moons can't grow larger inside the limit, but some objects were large when the system formed
131
What planet has the largest number of confirmed moons?
Jupiter
132
What moon has the largest rocky surface in the solar system?
Ganymede
133
Which moon might have oceans of liquid water under a frozen surface?
Europa
134
Why is Titan an interesting moon to study that we would dedicate so much probe time to this one moon?
Titan is an important moon to study because it is very similar to earth. It's atmosphere is 90% nitrogen, which makes up the majority of earth's atmosphere as well. It is also the second largest moon (largest including its atmosphere), which makes it a more prominent moon to study. It also reminds one of Venus, therefore learning about Venus and earth can reveal information about Titan's characteristics and patterns.
135
Discovery of Pluto
With fame of Neptune's discovery, people went looking for 'Planet X'
-PERCIVAL LOWELL urged the construction of the wide field camera (1916) - camera completed in 1929
CLYDE TOMBAUGH found Pluto 1930
-publicly announced Mar 13 1920 - anniversary of Uranus discovery
136
Pluto's orbit
The orbit for Pluto is highly elliptical
- it is sometimes closer to the Sun than Neptune (1979-99)
- it is also tipped 13 degrees with respect to the plane of the solar system
- all the planets are close to the plane
- was pluto really a planet?
137
James Christy
1978 he noted a bump on images of Pluto
- we know this as Pluto's moon Charon
- in size they are more of a double planet
- only with use of HST was it possible to separate the 2 objects
- might now be 4 additional moons (5 total)
- pluto might have also suffered a collision-ejection type formation
138
What is the nature of pluto and charon?
From the density it is estimated that they are both a mixture of rock and ice - densities are btwn the rocky inner planets and the gaseous outer planets
- from spectral observations pluto is known to have a tenuous atmosphere
- ----methane and CO2
- the true anther of these 2 worlds is unknown since we have never visited them
139
Spacecrafts to Pluto
Too far away to see its surface
- current mission to Pluto is NEW HORIZONS
- left Jan 19 2006
- closest approach on July 15, 2015
140
Pluto: planet or dwarf planet?
1922 JEWITT AND LUU discovered another object at 42 A.U. but only 240 km across
- it appeared reddish like Pluto
- since that time there have been 1000s if such objects discovered
- these are called KUIPER BELT OBJECTS (TRANS-NEPTUNIAN OBJECTS)
- Pluto became Trans-Neptunian Object #1
141
The Kuiper Belt
Theorized to be from about Pluto's orbit to 500 A.U.
- all evidence now is that they stop much sooner
- one of 2 reservoirs of potential comets
- lies in the plane of the solar system
Belt proposed in 1950s
- first by Edgeworth
- later by Kuiper
First object found was in 1992
142
Three classes of Kuiper Belt objects (KBOs)
Classical
- 42-48 A.U.
- Small eccentricities
- avoid Neptune and are in stable orbits
Scattered and Centaurs
- large eccentricities
- 35 A.U.
- can be perturbed by Neptune (potential source of short period comets)
Resonant
-in narrow orbits determined by Neptune (Pluto)
143
KBOs - largest known trans-Neptunian objects
A number of large ones
- Varuna (2000) a little smaller than Charon
- Quaoar (2002) about half size of Pluto
- Eris (2003) - bigger than Pluto
144
Eris
TNO
- discovered by Michael Brown
- just a little bigger than Pluto
- 67.6 A.U.
- orbit 557 years
145
Makemake
TNO
- Code named easterbunny since it was discovered around Easter 2005
- the creator of humanity from the mythos of the people of Easter Island (Rapa Nui)
- 46 A.U. currently at 52.3 A.U. 29 degree tip
- third largest dwarf planet
- doesn't have any moons
146
Haumea
TNO
- Hawaiian goddess of fertility and childbirth
- 2 moons
- 43 A.U. average distance from sun
- 29 degree tip
- 4th largest dwarf planet but is elongated due to fast rotation
147
Planet definition
A celestial body that:
1. is in orbit around the Sun
2. has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape
3. has cleared the neighborhood around its orbit
148
Dwarf planet definition
A celestial body that:
1. is i orbit around the sun
2. has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape
3. Has not cleared the neighborhood around its orbit
4. is not a satellite
ALL OTHER OBJECTS (Except satellites) orbiting the sun are referred to as "Small Solar System Bodies)
149
So what is a planet?
8 planets
- an IAU process will be established to assign borderline objects into either dwarf planet and other categories
- these currently include most of the solar system asteroids, most TNOs, comets, and other small objects
150
IAU Official dwarf planets
```
Pluto
Eris
Ceres
Haumea
Makemake
```
-2 don't have moons
151
Could be dwarf planets
Orcus, Quaoar, 2007 OR10, Sedna
152
Scattered TNO
Bc TNOs are similar in composition to comets that this is the source of short period comets
- A TNO is scattered by a gravitational encounter and sent in towards the Sun
- these comets have orbits of less than a few 100 AU in size
153
The OORT cloud
- long period comets have orbits that range from 10,000 to 100,000 AU
- can't come from Kuiper belt
- a second reservoir of comets was thus theorized by Oort in 1950
- it is a spherical distribution of icy objects
- no direct evident yet - although Sedna is a very interesting case
- ---too high for TNO and too low for classical Oort cloud
- --3 others with distances of 100s of AU
154
What year was Pluto discovered and by who?
1930 by Clyde Tombaugh
155
What are the dwarf planets?
```
Pluto
Ceres
Eris
Makemake
Haumea
```
156
T/F all of the dwarf planets orbit close to the plane of the overall solar system
FALSE
157
T/F all dwarf planets have at least one moon
FALSE
158
Compared to planets, what are the densities of dwarf planets?
Dwarf planets are less dense than terrestrial planets but more dense than Jovian worlds
159
Where do short period comets come from?
The Kuiper Belt
160
T/F we have no close up images of any dwarf planet?
TRUE
161
Who discovered the first Trans-Neptunian Object (not include Pluto)
Jewitt and Luu 1992
162
Asteroids
Were once called the Minor Planets (one is now a dwarf planet)
163
Position of the planets
1722 Johann Bode popularized a relation to predict the positions of the planets
Bode's Law
- sequence (0,3,6,9,12,24,48,96,etc.)
- add 4 and divide by 10
- this gives the distance of the planets in AU
- remember this was before the discovery of Uranus
164
Example of Bode's law
```
(0+4)/10 = 0.4 AU
-Mercury 0.39 AU
(3+4)/10 = 0.7 AU
-Venus 0.72 AU
...etc.
until
(24+4)/10 = 2.8 AU
-missing planet? btwn Mars (12) and Jupiter (48)
```
165
Search for Missing planet
Celestial Police
-1800 6 german astronomers searched
GIUSEPPE PIAZZI
- 1801 found first candidate
- named object Ceres (patron goddess of Sicily) - this is what caused all the problems in the IAU vote
- orbit was 2.77 AU (missing planet?)
Ceres structure
- large rocky inner core
- water ice layer
- thin dusty outer crust
166
Search for missing planet 2
1802 found Pallas (greek goddess of wisdom)
- orbit also 2.77 AU
- later 2 more large asteroids found with similar orbits - JUNO and VESTA (1804 and 1807)
- we know these objects to be part of the Asteroid Belt
167
Main belt asteroids
```
Ceres
Pallas
Juno
Vesta
Hygiea
```
168
The asteroid belt
it is estimated there could be as many as 100,000 in the belt that could be observed from earth
- these are often found by amateur astronomers
- if combined into one body it would be 1500 km in radius - the size of a small moon
One asteroid, IDA, was found to have a small moon
there are gaps in the belt called the Kirkwood gaps caused by the presence of Jupiter
169
Apollo Asteroids
- Cross the orbit of the earth
- these are ones to worry about
- Icarus, Hermes, XM1
- Dec. 19, 1994 - XM1 passed within 105,000 km of earth (about the size of a house) - were very worried about this one
170
Trojan Asteroids
- orbit 60 degrees in front of and behind Jupiter in its orbit
- one greek camp, one Trojan camp (Homer's story from trojan war)
- one traitor in each camp
- in stable Lagrangian points (L4 and L5)
- First discovered in 1906
171
Hilda family of asteroids
These are asteroids similar to the Trojan asteroids, but are in 3:2 resonance with jupiter
- can be directly opposite the sun from Jupiter, or pass through one of the 2 trojan asteroid points
- over three orbits they will be in one of three pointsC
172
Comet structure
"dirty snowball"
-fits the current model of the nucleus (few km across)
made of:
- water
- CO2
- Ammonia
- Methane
- a little bit of dust and rock mixed in
-temp. in outer solar system keep this ball frozen
173
What happens to comet as it approaches the sun
As snowball approaches the sun the temp. rises
- ices vaporized and dust liberated
- the gases glow as a fuzzy ball called the Coma (1 km in diameter)
- outside the coma is a larger sphere of hydrogen called 'hydrogen envelope'
- --10 million km in diameter
- --not visible to the naked eye
174
Comet tail
Coma material is pushed back by solar wind and radiation pressure to form the tail (can extend over 1 AU)
-makes comets the largest objects in the solar system
2 tails
- DUST tail (dust particle lagging behing comet in orbit
- ION tail (directly away from the sun - bluish tail in photos - made of ions pushed by solar wind
175
Famous comets
```
Halley's comet
Hyakutake
Ikeya-seki
Hale-Bopp
Comet West
```
176
Aftermath of comets
When comets pass through they leave material behind
-when earth passes through these areas we can have a meteor shower
Meteoroids are smaller versions of asteroids
- material floating through space
- until it hits the earth's atmosphere
177
Differentiated Asteroids
As the object is forming it is in a molten state
- the heavier elements sink to the center
- then the object cools over a long period of time
- this was true of the rocky planets and moons
- it is also true of asteroids which can then be broken up
178
Meteors
A meteor is the brief flash when a meteoroid hits the atmosphere and burns up
- sometimes called shooting stars
- could be dust or fairly large rocks
179
What happens if meteoroid hits the earth?
When a meteoroid makes it through the atmosphere and hits the earth it becomes a meteorite
- an estimated 300 tons of extraterrestrial rocks and dust fall on the earth each day
- most of this is in the form of dust or micrometeorites
- it's the rocks we have to worry about
180
Micrometeorites
Some of the extraterrestrial material that falls to the earth is magnetic in nature
- you can walk around with a strong magnet and pick up this material to look for micrometeorites
- you would then have to look through a microscope to see if it showed the characteristic shape and surface of a meteorite
- often you can't even see the micrometeorites you have picked up except through the telescope
181
Types of Meteorites
Chondrites
Achondrites
Irons
Stony-iron
182
Chondrites
82% of all meteorite falls
- make up the part of the stony group
- characterized by chondrules (small spheres of formally melted minerals)
- ordinary chondrites (73.5%)
- Carbonaceous Chondrites (3.6%)
- ---rare
- ---contain carbon, carbon compounds and perhaps even complex organic compounds, maybe amino acids
- ---might have building blocks of life
183
Achondrites
7. 8% - without chondrules
- another form of stony meteorites
- come from differentiated surface such as asteroids and planets
- if a differentiated asteroid is broken the surface layer can produce this type of meteorite
- some of these are believed to have knocked from the surface of the moon or mars
- stony meteorites have a fusion crust from entry through the atmosphere
184
Irons
About 4.8% of meteorites
- contain no stone
- may contain 10-20% nickel
- etched iron meteorites show Widmanstatten Pattern
- --long crystal structures (slow cooling)
- --think about the crystals on the highlands of the moon
- --no way to fake this feature
- this is impossible to counterfeit
- comes from the center of differentiated asteroids
185
Stone-iron
Equal amounts of rock and iron
- 1.2% of meteorites
- likely come from the boundary btwn the crust level and the iron core of asteroids
186
Which is the only member of the asteroid belt which is round in shape?
Ceres
187
T/F - All asteroids are contained in the asteroid belt?
FALSE
188
When we see a picture of a comet there is often a whitish tail and a bluish tail. What causes the WHITE tail we see?
Freed dust and gas that lags behind the head of the comet as it orbits the sun
189
What do we call the object that we pick up off the surface of the earth that might have been seen as a flash of light in the night time sky?
Meteorite
190
T/F - The ion tail of a comet points directly away from the sun
TRUE
191
Which asteroids are of most concern to those of us living on the earth?
Apollo Asteroids
192
If we merged all the asteroids in the asteroid belt into one object, how large would tho object be?
The size of a small moon
193
The nucleus of a comet most closely resembles what?
A trans-neptunian object (TNO)
194
T/F - if you do not find a Widmanstatten pattern in a stony meteorite you know it is fake
FALSE
195
Magellan Spacecraft
Went to Venus 1989
- objective was to map the surface of Venus and to determine the topographic relief of the planet
- provided clearest view ever of Venus
- revealed unique geological features, meteor impact craters, evidence of volcanic eruptions
196
Curiosity rover
Mars
- found that surface soil on red planet contains about 2% water by weight
- easily accessible water in the dirt
197
Who discovered pluto?
Clyde Tombaugh
198
Michael Brown
Discovered Eris
| -object led to the debate of Pluto actually being a planet or dwarf planet
199
Galileo disoveries
- Jupiter's 4 moons
- seas and features of moon
- phases of Venus
- sunspots
- also saw Neptune but thought it was a distant star
- and saw rings of Saturn
