Presentation on theme: "Our Solar System Origins of the Solar System Astronomy 12."— Presentation transcript:
1 Our Solar SystemOrigins of the Solar SystemAstronomy 12
2 Learning Outcomes (Students will…) -Explain the theories for the origin of the solar system -Distinguish between questions that can be answered by science and those that cannot, and between problems that can be solved by technology and those that cannot with regards to solar system formation. -Estimate quantities of distances in parsec. Estimate the age of the solar system. -Describe and apply classification systems and nomenclature used in the sciences. Classify planets as terrestrial vs. Jovian, inner vs. outer, etc. Classify satellites. Classify meteoroid, asteroid, dwarf planet, planet. Classify comets as long period vs. short period. etc -Formulate operational definitions of major variables. Given data such as diameter and density describe the properties that divide the planets and moons into groups. -Tools and methods used to observe and measure the inner and the outer planets and the minor members of the solar system
3 Our Solar System Our solar system is made up of: Sun Eight planets Their moonsAsteroids & MeteroidsComets
4 Inner PlanetsThe inner four rocky planets at the center of the solar system are:MercuryVenusEarthMars
5 Mercury Planet nearest the sun Second smallest planet Covered with cratersHas no moons or ringsAbout size of Earth’s moon
6 Venus Sister planet to Earth Has no moons or rings Hot, thick atmosphereBrightest object in sky besides sun and moon (looks like bright star)Covered with craters, volcanoes, and mountains
7 Earth Third planet from sun Only planet known to have life and liquid waterAtmosphere composed of Nitrogen (78%), Oxygen (21%), and other gases (1%).
8 Mars Fourth planet from sun Appears as bright reddish color in the night skySurface features volcanoes and huge dust stormsHas 2 moons: Phobos and Deimos
9 Asteroid BeltSeparates the inner, terrestrial planets from the outer, Jovian planetsContains ~100,000 asteroids.Largest known asteroid: 4 VestaLargest object : Ceres (dwarf planet)
10 Outer Planets The outer planets composed of gas are : Jupiter Saturn UranusNeptune
11 Jupiter Largest planet in solar system Brightest planet in sky At last count, 65 moons: 5 visible from EarthStrong magnetic fieldGiant red spotRings have 3 parts: Halo Ring, Main Ring, Gossamer Ring
12 Saturn 6th planet from sun Beautiful set of rings 62 moons Largest moon, Titan,Easily visible in the night skyVoyager explored Saturn and its rings.
13 Uranus 7th planet from sun Has a faint ring system 27 known moons Covered with cloudsUranus sits on its side with the north and south poles sticking out the sides.
14 Neptune 8th planet from sun Discovered through math 12 known moons Triton largest moonGreat Dark Spot thought to be a hole, similar to the hole in the ozone layer on Earth
15 A Dwarf PlanetPluto is a small solid icy planet is smaller than the Earth's Moon.
16 Pluto Never visited by spacecraft Orbits very slowly Charon, its moon, is very close to Pluto and about the same size
17 Two Types of Planets: Terrestrial and Jovian Why?
18 Asteroids Small bodies Believed to be left over from the beginning of the solar system billions of years ago100,000 asteroids lie in belt between Mars and JupiterLargest asteroids have been given names
19 Comets Small icy bodies Travel past the Sun Give off gas and dust as they pass by
23 How was the Solar System Formed? A viable theory for the formation of the solar system must be:based on physical principles (angular momentum, the law of gravity, the law of motions)able to explain all (at least most) the observable facts with reasonable accuracyable to explain other planetary systems
24 How was the Solar System Formed? A viable theory for the formation of the solar system must account for 4 characteristics:Patterns of motionTwo types of planetsAsteroids & cometsExceptions to patterns
25 Patterns of Motion All the planets orbit the Sun in the same direction The rotation axis of most of the planets and the Sun are roughly aligned with the rotation axis of their orbits.Orientation of Venus, Uranus, and Pluto’s spin axes are not similar to that of the Sun and other planets.Why do they spin in roughly the same orientation?Why are they different?
26 What does the solar system look like from far away? Sun, a star, at the centerInner (rocky) Planets (Mercury, Venus, Earth, Mars) ~ 1 AUAsteroid Belt ~ 3 AUOuter (gaseous) Planets (Jupiter, Saturn, Neptune, Uranus) ~ 5-40 AUKuiper Belt ~ 30 to 50 AU-includes PlutoOort Cloud ~ 50,000 AU
27 Bode’s LawA rough rule that predicts the spacing of the planets in the Solar SystemTo find the mean distances of the planets, beginning with the following simple sequence of numbers:With the exception of the first two, the others are simple twice the value of the preceding number.Add 4 to each number:Then divide by 10:Works for moons too!PlanetActual Distance (AU)Bode’s LawMercury0.390.4Venus0.720.7Earth1.001.0Mars1.521.6Jupiter5.205.2Saturn9.5410.0Uranus19.219.6Neptune30.138.8
28 Where are the asteroids? Most asteroids are located in two regions:Asteroid beltOrbit of Jupiter… the Hildas (the orange "triangle" just inside the orbit of Jupiter) and the Jovian Trojans (green). The group that leads Jupiter are called the "Greeks" and the trailing group are called the "Trojans"
29 Where are the comets? Kuiper Belt A large body of small objects orbiting (the short period comets <200 years) the Sun in a radial zone extending outward from the orbit of Neptune (30 AU) to about 100 AU. Pluto maybe the biggest of the Kuiper Belt object.Oort CloudLong Period Comets (period > 200 years) seems to come mostly from a spherical region at about 50,000 AU from the Sun.
30 Exceptions to Patterns Uranus has different axial tiltSome moons larger than othersSome moon have unusual orbits
31 Planetary Nebula or Close Encounter? Historically, two hypothesis were put forward to explain the formation of the solar system….#1 - Gravitational Collapse of Planetary NebulaSolar system formed form gravitational collapse of an interstellar cloud of gas#2 - Close Encounter (of the Sun with another star)Planets are formed from debris pulled out of the Sun during a close encounter with another star. But, it cannot account forThe angular momentum distribution in the solar system,Probability for such encounter is small in our neighborhood…Astronomers favour Hypothesis #1
32 The Nebular Theory* of Solar System Formation Interstellar Cloud (Nebula)*It is also called the ‘Protoplanet Theory’.Protoplanetary DiskProtosunGravitational CollapseMetal, RocksCondensation (gas to solid)SunGases, IceHeating Fission/Fusion(depends on temperature)Terrestrial PlanetsAccretionNebular CaptureJovian PlanetsAsteroidsLeftover MaterialsCometsLeftover Materials
33 Collapse of the Solar Nebula Gravitational CollapseDenser region in a interstellar cloud, maybe compressed by shock waves from an exploding supernova, triggers the gravitational collapse.Heating Protosun SunIn-falling materials loses gravitational potential energy, which were converted into kinetic energy. The dense materials collides with each other, causing the gas to heat up. Once the temperature and density gets high enough for nuclear fusion to start, a star is born.Spinning Smoothing of the random motionsConservation of angular momentum causes the in-falling material to spin faster and faster as they get closer to the center of the collapsing cloud.Flattening Protoplanetary disk.The solar nebular flattened into a flat disk. Collision between clumps of material turns the random, chaotic motion into a orderly rotating disk.This process explains the orderly motion ofmost of the solar system objects!
34 The Solar Nebula Hypothesis Basis of modern theory of planet formation.Planets form at the same time from the same cloud as the star.Immanuel Kant, ( ) German philosopher and scientist (astrophysics, mathematics, geography, anthropology) from East Prussia University of Königsberg, Königsberg now called KaliningradPlanet formation sites observed today as dust disks of T Tauri stars.Sun and our solar system formed ~ 5 billion years ago.
36 Planetesimals forming planets From the work of George Witherill, who was the director of DTM while Harold Williams was at DTM. He wrote me my hiring letter which brought me to the Washington Metro area at Alan Boss’ request.
37 Evidence for Ongoing Planet Formation Many young stars in the Orion Nebula are surrounded by dust disks:Probably sites of planet formation right now!
38 Dust Disks around Forming Stars Dust disks around some T Tauri stars can be imaged directly (HST).
39 The Story of Planet Building Planets formed from the same protostellar material as the sun, still found in the sun’s atmosphere.Rocky planet material formed from clumping together of dust grains in the protostellar cloud.Mass of less than ~ 15 Earth masses:Mass of more than ~ 15 Earth masses:Planets can grow by gravitationally attracting material from the protostellar cloudPlanets can not grow by gravitational collapseEarthlike planetsJovian planets (gas giants)
40 Extrasolar PlanetsAn extrasolar planet, or exoplanet, is a planet beyond our solar system, orbiting a star other than our SunInformation obtained primarily from wikipedia.org
41 Types of Extrasolar Planets Hot JupiterA type of extrasolar planet whose mass is close to or exceeds that of Jupiter (1.9 × 1027 kg), but unlike in the Solar System, where Jupiter orbits at 5 AU, hot Jupiters orbit within approximately 0.05 AU of their parent stars (about one eighth the distance that Mercury orbits the Sun)Example: 51 Pegasi b
42 Types of Extrasolar Planets Pulsar PlanetA type of extrasolar planet that is found orbiting pulsars, or rapidly rotating neutron starsExample: PSR B in the constellation Virgo
43 Types of Extrasolar Planets Gas GiantA type of extrasolar planet with similar mass to Jupiter and composed on gasesExample: 79 Ceti b
44 Methods of Detecting Extrasolar Planets Transit MethodIf a planet crosses ( or transits) in front of its parent star's disk, then the observed visual brightness of the star drops a small amount.The amount the star dims depends on the relative sizes of the star and the planet.
45 Methods of Detecting Extrasolar Planets AstrometryThis method consists of precisely measuring a star's position in the sky and observing how that position changes over time.If the star has a planet, then the gravitational influence of the planet will cause the star itself to move in a tiny circular or elliptical orbit.If the star is large enough, a ‘wobble’ will be detected.
46 Methods of Detecting Extrasolar Planets Doppler Shift (Radial Velocity)A star with a planet will move in its own small orbit in response to the planet's gravity. The goal now is to measure variations in the speed with which the star moves toward or away from Earth.In other words, the variations are in the radial velocity of the star with respect to Earth. The radial velocity can be deduced from the displacement in the parent star's spectral lines (think ROYGBIV) due to the Doppler effect.A red shift means the star is moving away from EarthA blue shift means the star is moving towards Earth
47 Methods of Detecting Extrasolar Planets Pulsar TimingA pulsar is a neutron star: the small, ultra-dense remnant of a star that has exploded as a supernova.Pulsars emit radio waves extremely regularly as they rotate. Because the rotation of a pulsar is so regular, slight changes in the timing of its observed radio pulses can be used to track the pulsar's motion.Like an ordinary star, a pulsar will move in its own small orbit if it has a planet. Calculations based on pulse-timing observations can then reveal the geometry of that orbit
48 Methods of Detecting Extrasolar Planets Gravitational MicrolensingThe gravitational field of a star acts like a lens, magnifying the light of a distant background star. This effect occurs only when the two stars are almost exactly aligned.If the foreground lensing star has a planet, then that planet's own gravitational field can make a detectable contribution to the lensing effect.
49 Methods of Detecting Extrasolar Planets Direct ImagingPlanets are extremely faint light sources compared to stars and what little light comes from them tends to be lost in the glare from their parent star.It is very difficult to detect them directly. In certain cases, however, current telescopes may be capable of directly imaging planets.