The Origin of the Solar System Movie: The History of the Solar System Please swipe your ID for attendance tracking and take your assigned transmitter.

How old is the Solar System? :10 0 of 5 1)1.3 million years 2)350 million years 3)1.7 billion years 4)4.5 billion years 5)13 billion years

Visible Barnard 68 Star formation ← collapse of the cores of giant molecular clouds: Dark, cold, dense clouds obscuring the light of stars behind them. The Formation of Stars: Giant Molecular Clouds

Which wavelength range is adjacent to the visible spectrum and has longer wavelengths than visible light? :10 0 of )X-rays 2)Gamma-Rays 3)Stingrays 4)Infrared light 5)Ultraviolet light

Visible Infrared Barnard 68 Star formation ← collapse of the cores of giant molecular clouds: Dark, cold, dense clouds obscuring the light of stars behind them. (More transparent in infrared light.) The Formation of Stars: Giant Molecular Clouds

Parameters of Giant Molecular Clouds Size: r ~ 50 pc Mass: > 100,000 M sun Dense cores: Temp.: a few 0 K R ~ 0.1 pc M ~ 1 M sun

(Bok) Globules ~ 10 – 1000 solar masses; Contracting to form protostars Compact, dense pockets of gas which may contract to form stars.

Protostars Protostars = pre-birth state of stars: Hydrogen to Helium fusion not yet ignited Still enshrouded in opaque “cocoons” of dust => barely visible in the optical, but bright in the infrared.

Do you expect stars to form isolated? :10 0 of )Yes. 2)No, they should form in groups of a few (2 – 5) 3)No, they should form in large groups (several 100s or 1000s) 4)No, actually all stars in a galaxy (several billions) should form at the same time.

Open Clusters of Stars Large masses of Giant Molecular Clouds => Stars do not form isolated, but in large groups, called Open Clusters of Stars. Open Cluster M7

What happens to a spinning object if it contracts? :10 0 of )It stops rotating. 2)Its rotation slows down. 3)Its rate of rotation remains unchanged. 4)Its rotation speeds up.

Protostellar Disks Conservation of angular momentum leads to the formation of protostellar disks → birth place of planets and moons

The Solar Nebula Hypothesis Planets form at the same time from the same cloud as the star. Sun and our Solar system formed ~ 4.6 billion years ago. Planet formation sites observed today as dust disks of T Tauri stars.

Would you expect that other stars have planetary systems too? :10 0 of )Yes. 2)No.

Extrasolar Planets All stars have gone through basically the same formation process as the sun. → Many stars should have planets! Extrasolar planets can not be imaged directly. → planets orbiting around other stars = “Extrasolar planets” Detection using the “wobbling” technique: Look for “wobbling” motion of the star due to the gravitational pull of the planet on the star.

Would you expect that there are still new solar systems being formed at this time? :10 0 of )Yes. 2)No.

Evidence for Ongoing Planet Formation Many young stars in the Orion Nebula are surrounded by dust disks: Probably sites of planet formation right now!

Dust Disks around Forming Stars Dust disks around some T Tauri stars can be imaged directly (HST).

What is radioactivity? :10 0 of )The decay of atomic nuclei, resulting in the emission of radio waves. 2)The decay of atomic nuclei, resulting in the emission of gamma-rays. 3)The fusion of atomic nuclei, resulting in the emission of radio waves. 4)The fusion of atomic nuclei, resulting in the emission of gamma-rays. 5)The emission of radio waves by stars like our sun.

The Age of the Solar System Sun and planets should have about the same age. Ages of rocks can be measured through radioactive dating: Measure abundance of a radioactively decaying element to find the time since formation of the rock Dating of rocks on Earth, on the Moon, and meteorites all give ages of ~ 4.6 billion years.

If you start out with 1 kg of a radioactive substance with a half-life of 150 years, how long does it take until there is nothing left? :10 0 of )150 years. 2)300 years. 3)1,500 years. 4)An infinite amount of time (in principle). 5)Impossible to tell with the given information.

What is “condensation”? :10 0 of )The melting of a substance. 2)The transition of a substance from the liquid to the gas phase. 3)The transition of a substance from the gas to the liquid phase. 4)The transition of a substance from the liquid to the solid phase.

Condensation in the Early Solar System Only condensed materials could stick together to form planets Temperature in the protostellar cloud decreases outward. Further out → Protostellar cloud cooler → metals with lower melting point condensed → change of chemical composition throughout solar system Lighter substances condense at lower temperatures. → Average density of planets decreases outwards!

Formation and Growth of Planetesimals Planet formation starts with clumping together of grains of solid matter: Planetesimals Planetesimals (few cm to km in size) collide to form planets. Planetesimals grow through condensation and accretion.

What happens if you try to mix oil and water? :10 0 of )They will mix to a uniform solution. 2)The oil will sink to the bottom, the water will “swim” on top of it. 3)The water will sink to the bottom, the oil will “swim” on top of it.

The Growth of Protoplanets As rocks melted, heavier elements sink to the center → differentiation → Terrestrial planets have heavy-metal (iron) cores and mantles of lighter substances

The Story of Planet Building Planets formed from the same protostellar material as the sun. Rocky planet material formed from clumping together of dust grains in the protostellar cloud. Mass of less than ~ 15 Earth masses: Planets can not grow by gravitational collapse Mass of more than ~ 15 Earth masses: Planets can grow by gravitationally attracting material from the protostellar cloud Earthlike planets Jovian planets (gas giants)

Which features on the surface of the moon tell us that there were many small bodies (rocks) remaining in the solar system after it formed? :10 0 of )A dense atmosphere. 2)The large, uncratered maria. 3)Lots of impact craters in the lunar highlands. 4)High mountains.

Clearing the Nebula Surfaces of the Moon and Mercury show evidence for heavy bombardment by asteroids. Remains of the protostellar nebula were cleared away by: Sweeping-up of space debris by planets Ejection by close encounters with planets

Ejection of small bodies by massive planets

Clearing the Nebula Surfaces of the Moon and Mercury show evidence for heavy bombardment by asteroids. Remains of the protostellar nebula were cleared away by: Radiation pressure of the sun Solar wind Sweeping-up of space debris by planets Ejection by close encounters with planets

Final overview movie