Solar System Read Your Textbook: Introduction to Physical Science –Chapter 20 –Chapter Answer Questions –Chapter 20: Q4;P1,4,6,9 W3 –Chapter 21: Q2,5-8 P2,3 W3 –Chapter 22: Q1-3,12;P2,3,7 W1,4 –Chapter 23: Q2,4,6,9 W1

Solar System Scale The Sun has % of the mass of the solar system Jupiter has 2/3 of the remaining that formed planets

Planetary Orbital Inclination Our Solar System is Very Nearly Disk Shaped Angles of the planets orbits are shown with respect to the ecliptic (earth-sun orbit).

Planetary Densities moon

Terrestrial (Earth-Like) Planets –High Densities (mostly metals and solids) –Small sizes –Near the Sun Jovian (Jupiter-Like) Planets –Low Average Densities (mostly gases and ices) –Large sizes –Far from the Sun Two Planet Types

Terrestrial Rock Samples (Greenland, Canada, Australia) –3.9 billion years Lunar Rock Samples (Apollo Missions) –4.1 billion years Meteorite Samples –4.5 billion years Solar modeling The solar system is roughly billion years old. Ages Determined

Solar Nebula Theory A complete description of the formation of the solar system must explain the observed characteristics:

Disk-like Nature A complete description of the formation of the solar system must explain the observed characteristics: The disk shape nature of the solar system –All planets orbit within 10 degrees of the Earth-Sun orbit –Common Rotations and Revolutions

Density Variations A complete description of the formation of the solar system must explain the observed characteristics: The disk shape nature of the solar system –All planets orbit within 10 degrees of the Earth-Sun orbit –Common Rotations and Revolutions Terrestrial (Earth-Like) Planets –high density, rocky, small, close to the sun Jovian (Jupiter-Like) Planets –low density, gaseous, large, farther away from the sun

Common Age A complete description of the formation of the solar system must explain the observed characteristics: The disk shape nature of the solar system –All planets orbit within 10 degrees of the Earth-Sun orbit –Common Rotations and Revolutions Terrestrial (Earth-Like) Planets –high density, rocky, small, close to the sun Jovian (Jupiter-Like) Planets –low density, gaseous, large, farther away from the sun Common Ages Space Debris –asteroids, comets, ring systems

Orion Star formation region in the constellation of Orion visible to the unaided eye.

Star Formation Regions Belt and Sword of Orion Orion Nebula & Horse Head Nebula

Nebulosity Hot new stars illuminate the gas and dust of the horse head nebulae in Orion

Infant Stars Orion Nebula Trapezium

Stellar Nurseries New, Young stars are associated with gas and dust. Eagle Nebula

A Star is Born

Proto-Stars The Orion Trapezium Region in Infra-Red Light

Angular Momentum Conservation The ice skater, the ballerina, the earth’s rotation and a child’s top, believe it or not, all have a lot to do with each other, and the formation of the solar system. Angular Momentum: –Rotating Objects Have It –They Want To Conserve It Depends on Mass Depends on velocity Depends on Distribution of Matter About the Rotation Axis

Sphere To Disk When a spherical proto-stellar cloud begins collapsing, it has some inherent rotation (and thus angular momentum) associated with it. As material moves to smaller radii, the rotation increases, like the ice skater and ballerina in a spin bringing their arms in toward the rotational axis. Material along the axis does not spin as much as material near the “equator” and so does not have as much angular momentum to save. Therefore, the material at the poles falls closer to the center.

Rotation Gravitationally collapsing rotating spheres tend to create flattened spinning disks. The inner parts of the disk rotate faster than the outer parts.

Solar Nebula Solar System Formation

Proto-Stellar Disk Radiation from the new star, tries to escape. The infalling disk material absorbs it and cuts it off. Its only escape is along the poles of rotation where the disk is thinner.

Eta Carina

 Pictoris Disk material around other stars.

Proto-Stellar Accretion Disk Bi-Polar Outflow

Planetary Orbits KEPLER'S III LAW: THE RELATION BETWEEN ORBITAL PERIOD P (years) AND AVERAGE DISTANCE a (A.U.) IS A CONSTANT FOR THE SOLAR SYSTEM P 2 /a 3 = constant

Planetesimal Coalescence Eddies, whirlpools, and other density variations cause planetesimals which later accrete and collide to form into the planets.

Proto-planet Accretion & Coalescence N-body Coalescence

Planetary Densities

Condensation Temperature Temperature decreases with distance from the sun. Temperature (K) Distance (Astronomical Units A.U.) Mercury Earth Jupiter SaturnPluto Metal Oxides Metallic Iron and Nickel Silicates Sulfides Water Ice Ammonia and Methane Ices

Solids and Density Density decreases with distance from the sun also in the same way that the temperature does. Only matter with higher density, existed as solids (not gas) at the higher temperatures found near the proto-sun. Distance (Astronomical Units A.U.) Temperature (K) Mercury Earth Jupiter SaturnPluto Metal Oxides Metallic Iron and Nickel Silicates Sulfides Water Ice Ammonia and Methane Ices

Solar Nebula Composition The denser materials are able to exist as solids at higher temperatures. The only solids found in the inner portions of the solar nebula are the dense metals that form the rocky terrestrial planets. This dense material also exists at large radii from the proto-sun. Less dense ices only exist in the outer solar nebula.

Pressure Balancing Gravity When the star begins generating energy within, radiation and gas pressure build up to counteract gravity. Radiation and winds move outward, away from the star.

Density Evolution The initial distribution of material in the solar nebula (A) changes, as the sun accretes material and finally “turns ON” (B), and material is blown out of the interior (C). Density (g/cm 3 ) Distance (Astronomical Units A.U.) Mercury Earth Jupiter SaturnPluto A B C

Terrestrials versus Jovian Planets Terrestrial planets formed from the materials that could exist at the highest temperatures. They are higher density rocky bodies close to the proto-sun. Jovian planets formed from both high density and the much more abundant low density material that was able to exist as solids far from the proto-sun. There was much more material to draw from (both metals and ices) as compared to material the terrestrial planets had available. Therefore, the jovian planets are less dense and farther from the sun. Why are the Jovian planets so much larger?

Clearing the Inner Disk Once the Sun had “turned-ON”, the material in the inner disk was blown clear, thus truncating the accretion and coalescence processes of the terrestrial planets. Their growth was “stunted” by the birth of our Sun. The jovian planets were able to draw on the metals and much more abundant ices and grew very large. Jupiter is the largest planet probably because: –It is the nearest “far” planet (existed in a higher density region) –More numerous ices could also be accreted as well as metals –Not stunted by clearing of the inner disk (may have benefited)

Are We Unique? Solar Nebula Theory Explains –The disk shape nature of the solar system, including orbits –Existence of Terrestrial Planets –Existence of Jovian Planets –Common Ages (Everything Formed At Once) –Space Debris (Left Over Junk) –Planets form as a by-product of star formation Solar Nebula Theory Predicts –Accretion disks should be found around young stellar systems –Planets form as a by-product of star formation –Terrestrials close, Jovians far, and a large “Jupiter” in the middle The sky should be full of solar systems of similar nature!