THE BIRTH OF THE SOLAR SYSTEM

MODELS OF THE SOLAR SYSTEM Geocentric - Everything revolved around earth. (Aristotle and Ptolemy) Heliocentric – Planets revolved around the sun – Galileo - saw four moons revolving around Jupiter (1610)

SOLAR SYSTEM FACTS 1. Planets are isolated 2. Orbits are in the same plane along an elliptical path 3. Planets (and moons) travel along orbits in same direction…. same direction as Sun rotates (counterclockwise viewed from above)

SOLAR SYSTEM FACTS 4. Almost all objects rotate in the same direction (except Venus)

SOLAR SYSTEM FACTS 5. The solar system is highly differentiated (separation of densities) Terrestrial Planets (rocky, dense with density ~4-5 g/cm3) Jovian Planets (light, gassy, H, He, density 0.7-2)

SOLAR SYSTEM FACTS 6. All objects have similar ages.

NEBULAR HYPOTHESIS Nebular Hypothesis – the widely accepted hypothesis, explaining the steps of the formation of the solar system

NEBULAR HYPOTHESIS Nebular Hypothesis 1.Supernova 2.Solar Nebula 3.Gravitational Collapse 4.Accretion Disk 5.Protostar 6.Planetesimals 7.Protoplanets 8.Inner and Outer Planets 9.Solar Wind

SUPERNOVA ( LIFE BEGINS WITH DEATH) Supernova – an explosion from the death of star, scattering massive amounts of matter and energy across space.

SOLAR NEBULA (OR PLANETARY NEBULA) Nebula a large cloud of interstellar gas and dust. These are dense clouds of hydrogen and helium and are gravitationally unstable. Orion Nebula

GRAVITATIONAL COLLAPSE & ACCRETION DISK The cloud shrinks in size as it collapses under it’s own gravity. It then begins to rotate due angular momentum. The spinning will increase in speed and flatten out into a thick disk called an accretion disk.

“SPIN-UP” EFFECT It is what causes the pizza dough to flatten out when tossed or an ice skater to spin-up as she pulls her arms and legs in close to her body.

ANGULAR MOMENTUM Angular momentum keeps the dust and gas from falling straight to the center, but rather spiraling down into a flattened disk.

PROTOSTAR (SHINING STAR) As the disk forms due to gravitational collapse, and as energy is gained from friction, a star begins to form in the center. After enough mass is gathered in the center, to reach temperatures of ~10,000,000 K, fusion takes place, and the star shines.

PLANETESIMALS AND CONDENSATION Close to the protosun the grains are heavy elements or “rocky” materials. Farther out, the grains are icy, “gas” materials. Frost line – the line that seperates rock planets from gas planets. Close to the sun it is hot, further away, it is cold. Condensation – the process of going from a gas to a solid or a liquid. This temperature is different for different elements.

PLANETESIMALS AND CONDENSATION Close to the Sun, the planetesimals look like asteroids. Far from the Sun, the planetesimals are a mix of ice and rock. The dust grains, about the size of smoke particles, are charged with static electricity. Accretion is a snowball effect that builds larger and larger materials into planetesimals.

PROTOPLANETS Planetesimals collide to form protoplanets. The larger the protoplanet, the stronger its gravity is. The stronger its gravity, the more it attracts stuff and the more violent the collisions become. 8eJM30k8www.youtube.com/watch?v=qgm 8eJM30k8

NEBULAR HYPOTHESIS Nebular Hypothesis – the widely accepted hypothesis, explaining the steps of the formation of the solar system

AGE OF THE SOLAR SYSTEM The solar system formed:4.56 billion years ago Evidence: 1.Lunar samples to 4.6 Ga 2.Meteorites Ga 3.Rocks from Earth – 3.9 (or 4.4 Ga) Also, we can view infant solar systems with the hubble telescope.