the planets - samsi · venus 0 243 d(retrograde) earth 1 23.9 h mars 2 24.6 h jupiter 16 9.8 h ......

AST 303: Chapter 1

The Planets

• The planets, in order from the Sun, are:MercuryVenusEarthMarsJupiterSaturnUranusNeptunePluto

AST 303: Chapter 2

Characteristics Of The Planets (1)

Mass Radius Density (H2O)Mercury 0.06 0.38 5.46Venus 0.82 0.95 5.27Earth 1.00 1.00 5.52Mars 0.11 0.53 3.91Jupiter 318 11.2 1.25Saturn 95 9.4 0.63Uranus 15 4.0 1.28Neptune 17 3.8 1.72Pluto 0.0022 0.18 2.10

AST 303: Chapter 3


Mass Radius Density (H2O)Mercury 0.06 0.38 5.46Venus 0.82 0.95 5.27Earth 1.00 1.00 5.52Mars 0.11 0.53 3.91Jupiter 318 11.2 1.25Saturn 95 9.4 0.63Uranus 15 4.0 1.28Neptune 17 3.8 1.72Pluto 0.0022 0.18 2.10

AST 303: Chapter 4

Sizes of Planets, Compared to Sun

AST 303: Chapter 5

A Curious Relationship

• The Bode-Titius “law” is a regularity in the spacing of the planets. The“law” is not significant in itself, but the fact that the planets are spacedregularly is significant. Nonetheless, a statistician might find the agreementbetweeen the “law” and the data intriguing

Distance FormulaMercury 0.39 0.4 = ( 0 + 4)/10Venus 0.72 0.7 = ( 3 + 4)/10Earth 1.00 1.0 = ( 6 + 4)/10Mars 1.52 1.6 = ( 12 + 4)/10Asteroids (ave) 2.8 = ( 24 + 4)/10Jupiter 5.20 5.2 = ( 48 + 4)/10Saturn 9.55 10.0 = ( 96 + 4)/10Uranus 19.20 19.6 = (192 + 4)/10Neptune 30.09 38.8 = (384 + 4)/10Pluto 39.5 77.2 = (768 + 4)/10

AST 303: Chapter 6


Major Satellites RotationMercury 0 59 DVenus 0 243 D(Retrograde)Earth 1 23.9 HMars 2 24.6 HJupiter 16 9.8 HSaturn 18 10.2 HUranus 18 24 H(Retrograde)Neptune 8 18.4 HPluto 1 6 D

AST 303: Chapter 7


Major Satellites RotationMercury 0 59 DVenus 0 243 D(Retrograde)Earth 1 23.9 HMars 2 24.6 HJupiter 16 9.8 HSaturn 18 10.2 HUranus 18 24 H(Retrograde)Neptune 8 18.4 HPluto 1 6 D

AST 303: Chapter 8

Terrestrial (Dwarf) Planets

• There are two main groups of planets: The Terrestrial (Dwarf)planets and the Jovian (Giant) planets. The Terrestrial planetsare characterized as follows:• Small, not massive (Earth is biggest)• Dense (about 5 times that of water)• Near Sun; high temperature• Composed of heavy elements: Si, Fe, O, etc.• Thin or nonexistent atmospheres• Few or no satellites

AST 303: Chapter 9

Terrestrial Planets

AST 303: Chapter 10

Portrait of Terrestrial Planets and Some Satellites

AST 303: Chapter 11

Mercury from Space

AST 303: Chapter 12

Earthbased Views of Venus

AST 303: Chapter 13

Earthbased Views of Venus

Note atmosphere!

AST 303: Chapter 14

Venus from Space

AST 303: Chapter 15

Venus (Radar Topography)

AST 303: Chapter 16

Venus (Radar Topography)

AST 303: Chapter 17

Venus Surface (Venera)

AST 303: Chapter 18

Mars Drawings

AST 303: Chapter 19

Mars Drawings

AST 303: Chapter 20

Mars Drawings

AST 303: Chapter 21

Mars Photos (Earthbased)

AST 303: Chapter 22

Mars—Seasons

AST 303: Chapter 23

Map of Mars

AST 303: Chapter 24

Mars Closeups

AST 303: Chapter 25

Mars Closeups

AST 303: Chapter 26

Mars Closeups

AST 303: Chapter 27

Mars Closeups

AST 303: Chapter 28

Mars Closeups

AST 303: Chapter 29

Mars Closeups

AST 303: Chapter 30

Mars Closeups

AST 303: Chapter 31

Mars Closeups

AST 303: Chapter 32

Mars Closeups

AST 303: Chapter 33

Mars’ Satellites

AST 303: Chapter 34

Phobos

AST 303: Chapter 35

Atmospheres of Earth and Venus

AST 303: Chapter 36

Atmospheres of Earth and Mars

AST 303: Chapter 37

Minor Planets (Asteroids) —(1)

• Between the orbits of Mars and Jupiter are thousands of minorplanets (sometimes called asteroids)

• These are probably the remnants of material that never formedinto a major planet

• They show evidence of having collided and broken up overthe ages

AST 303: Chapter 38

Portraits of Some Minor Planets

AST 303: Chapter 39


• There is a group of minor planets (the Trojan asteroids) at thesame distance from the Sun as Jupiter, but leading or lagingby an average 60 degrees:

AST 303: Chapter 40


• Also, there are gaps—the so-called “Kirkwood gaps”—in theasteroid belt near periods which are simple fractions ofJupiter's period. The density of asteroids in the gaps isdepleted.

Jupiter

Kirkwoodgap atabout1/2 ofJupiter’speriod

Sun

Trojans (Trojan group)

Trojans (Greek group)

AST 303: Chapter 41

Minor Planet Ida

AST 303: Chapter 42

Meteorites (1)

• A meteor is a chunk of material (which could be of cometaryor asteroidal origin) that falls into our atmosphere and isheated to a high temperature, vaporizing and forming a streakin the sky. Sometimes the object explodes in a very brightevent known as a fireball or bolide. Most meteors do notreach the ground, but vaporize completely in our atmosphere.The larger ones that do reach the ground are called meteorites.

• Until recently, meteorites were the only objects from outerspace that astronomers could actually touch and analyze.

AST 303: Chapter 43

Grazing Meteor

AST 303: Chapter 44

Large Meteorite

AST 303: Chapter 45

Murchison Carbonaceous Chondrite

AST 303: Chapter 46

Meteorites (2)

• Meteorites fall into several classes: The main types are stones(similar to silicate rocks on Earth), irons and (a mixture)stony-irons. Among the stones are a class called carbonaceouschondrites that contain significant amounts of carbon andorganic compounds, and are believed to be very primitive.Amino acids-the building blocks of proteins-have beendetected in some carbonaceous chondrites. These amino acidsare clearly of extraterrestrial origin and are not contaminants,because they contain both “handedness” of the molecules,whereas life on Earth consists entirely of the left-handedvariety.

• The irons show evidence of once having been molten. Bypolishing and etching an iron meteorite, you can see largecrystal formations known as Widmanstätten patterns.

AST 303: Chapter 47

Meteorites (3)

• Finds versus falls: A meteorite fall is when we recover ameterorite that we saw fall so that we knew where to look.

• A find is when we accidentally discover a previouslyunknown meteorite.

• Over 2/3 of the finds are irons, but over 90% of the falls arestones.• Selection effect…

AST 303: Chapter 48

Craters

• When a very large meteorite hits the earth, it can cause a largecrater. These craters are also called “astroblemes.” Barringercrater in Arizona is the best-known of them, but it is only onemile in diameter and is far from being the largest.

• Satellite photographs of the Earth have led to the discovery ofmany very ancient craters, previously unknown. The largest,in South America, is about 120 km in diameter.

AST 303: Chapter 49

Barringer Crater

AST 303: Chapter 50

Old Meteor Crater

AST 303: Chapter 51


• Some minor planets have orbits that are very different fromthe ones we have discussed. There are minor planets such asEros that come quite close to the Earth; and others that havehighly elliptical orbits very unlike the nearly circular orbits ofthe main-belt asteroids, but rather similar to the orbits of somecomets.

• It is tempting to speculate that the asteroids with highlyelliptical orbits are actually “burnt-out” comets. Since manyof them also have unusual colors, this is a reasonablespeculation.

AST 303: Chapter 52

Comet-like Orbits of Some Minor Planets

AST 303: Chapter 53

Meteor Showers

• There are two classes of meteors: sporadic meteors, that comeat unpredictable times and from unpredictable directions; andshower meteors. The latter are seen every year, alwaysassociated with a particular part of the sky. They are oftenassociated with a known comet, and are believed to be debrismoving in the same orbit as the comet, that the Earth passesnear every year.

Meteor Shower

AST 303: Chapter 54

Comet Shoemaker-Levy

AST 303: Chapter 55

Orbits of Meteor Streams

AST 303: Chapter 56

Jovian (Giant) Planets

• The Jovian planets have the following characteristics:• Large, massive (Neptune is smallest)• Not dense (about same as water)• Far from Sun; low temperature• Composed of hydrogen, mostly, with helium as a second

constituent. May have rocky cores.• Thick, dense atmospheres.• Multiple satellites

AST 303: Chapter 57

Jupiter and Saturn

AST 303: Chapter 58

Uranus and Neptune

AST 303: Chapter 59

Earthbased Photograph of Jupiter

AST 303: Chapter 60

Jupiter Structure

AST 303: Chapter 61

Spots, Cloud Belts, and Moons

AST 303: Chapter 62

Spots

AST 303: Chapter 63

Galilean Satellites

AST 303: Chapter 64

Io as Pizza Pie

AST 303: Chapter 65

Io Showing “Lava” Flows of Sulfur

AST 303: Chapter 66

Io

AST 303: Chapter 67

Europa

AST 303: Chapter 68

Europa (Surface)

AST 303: Chapter 69

Ganymede

AST 303: Chapter 70

Ganymede (Surface)

AST 303: Chapter 71

Callisto

AST 303: Chapter 72

Jupiter Ring

AST 303: Chapter 73

Saturn (Earthbased Photograph)

AST 303: Chapter 74

Voyager Saturn

AST 303: Chapter 75

Saturn’s Atmosphere

AST 303: Chapter 76

Saturn’s Atmosphere

AST 303: Chapter 77

Saturn

AST 303: Chapter 78

Voyager Rings

AST 303: Chapter 79

Spokes and Dusky Lanes

AST 303: Chapter 80

Rings, with a Satellite

AST 303: Chapter 81

Ring and Satellite; Braided Ring

AST 303: Chapter 82

Mimas

AST 303: Chapter 83

Enceladus

AST 303: Chapter 84

Titan

AST 303: Chapter 85

Titan’s Atmosphere and Weather

AST 303: Chapter 86

Groundbased Picture of Uranus and Moons

AST 303: Chapter 87

Uranus: The Planet That Got Knocked On Its Side

AST 303: Chapter 88

Seasons on Uranus

AST 303: Chapter 89

Uranus From Space

AST 303: Chapter 90

Uranus and 5 Satellites

AST 303: Chapter 91

Miranda

AST 303: Chapter 92

Miranda

AST 303: Chapter 93

Ariel

AST 303: Chapter 94

Titania

AST 303: Chapter 95

Discovery of Uranian Rings

AST 303: Chapter 96

Uranian Ring System

AST 303: Chapter 97

Uranian Rings

AST 303: Chapter 98

Uranian Rings

AST 303: Chapter 99

Neptune with Satellite (Groundbased)

AST 303: Chapter 100

New Neptunian Satellites


Neptune Ring


Neptune and Blue Spot


Blue Spot Changes


Blue Spot


Other Spots


Triton


Nereid


Pluto: A Planet?

• Pluto is a special case. It is not massive, and has only onesatellite, but is of low density and far from the Sun.

• Recent discoveries of a new class of Pluto-like objects haverevised thinking about Pluto• Many would not classify it as a planet at all, but rather as

the first-discovered of this new class of objects• …but, the question is really one of definition, not science• Gerard Kuiper had predicted that there would be a belt

containing many objects roughly beyond Pluto’s orbit; itappears that these newly-discovered objects are from thelong-sought Kuiper Belt, and Pluto was just the first-discovered of these objects.


Pluto Discovery Plates (Blink)


Pluto Discovery Plates


Pluto and Charon


Comets (3)

• Comets are believed to represent the most primitive andunaffected material of the solar system. Therefore we maydiscover clues about the origin of the solar system by studyingthem.

• The “Stardust” mission that landed this week is intended tostudy this material

Stardust portrait ofComet Wild 2


Comets (3)

• Comets are believed to represent the most primitive andunaffected material of the solar system. Therefore we maydiscover clues about the origin of the solar system by studyingthem.

• The best model for a comet is Whipple’s “Icy Conglomerate”or “dirty snowball” model. The comet itself is a chunk ofvarious ices, dust, and other particles, which undergoesevaporation as the comet nears the Sun.

• Whipple’s model was confirmed by the various probes thatwere sent to Halley’s comet during the 1986 apparition. Onesurprise was that the comet nucleus itself was very black—noone had expected this!


Comet Halley


Comet Halley 1986


Comet Halley 1986—Solar Wind


Simultaneous Dust and Gas Tails


Comets (1)

• The elongated orbits of comets show that they are associatedwith the outer parts of our solar system. The orbits of cometsare oriented somewhat randomly with respect to the planets.


Types of Cometary Orbits


Escape From the Solar System


Origin Of Comets (1)

• Periodic comets like Halley’s reappear on a regular schedule.Calculations based on the amount of material they containshow that they would “wear out” after a few hundredapparitions; hence the comets we see must be relatively young.

• Halley’s comet has a period of 76 years. 300 apparitions ofHalley’s comet would be only 300 ×75 years or about 25,000years.

• The solar system is 4.5 billion years old.• Therefore comets are young, compared to the age of the solar

system.• How can the comets be young, if they represent the oldest

and least affected material in our solar system?


Aging of a Comet


Origin Of Comets (2)

• Oort proposed that there is a cloud of comets left over fromthe formation of the solar system, well beyond the orbits ofNeptune and Pluto (thousands of AU)

• Every so often, gravitational disturbances of passing stars willsend comets into the inner parts of the solar system.

• The reservoir of comets (“Oort cloud”) would be very large,and would provide a constant source of new comets,explaining why we still see them today.

• This also explains why the orbits of comets are so elongated.


Oort Cloud


Statistical Issues

• Historically, astronomy was the driver behind thedevelopment of many statistical methods• Gauss’ least squares for combining an overdetermined data

set to estimate orbital parameters of an object• Laplace developed Bayesian methods for astronomical as

well as other purposes. He expressed results in a typicalBayesian way (as the odds that the mass of Saturn laywithin a particular interval, for example)


Statistical Issues

• We’ve seen how the extraordinarily detailed pictures fromspace have dramatically improved understanding of planets.Thus, image analysis is an important statistical problem, toaccount for the instrumental signature

• In orbital analysis, estimating collision probabilities of a largeearth-orbit crossing object has become of increasing interest.If detected far enough in advance, it may be possible to avoida collision with Earth by slightly altering the orbitalparameters of the object with a space mission.

• Much needs to be learned about, e.g., the population ofKuiper belt and Oort cloud objects. We don’t see most ofthese objects: Can we nonetheless make useful inferencesabout these populations?

the planets - samsi · venus 0 243 d(retrograde) earth 1 23.9 h mars 2 24.6 h jupiter 16 9.8 h ......

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