FORMATION OF THE SOLAR SYSTEM

Section 19.3

http://science.nationalgeographic.com/science/space/solar-system

http://video.nationalgeographic.com/video/player/news/space-technology-news/solar-eclipse-2009-nasa.html

http://www.history.com/video.do?name=The_Universe

Objectives…

By the end of this section you WILL be able to…

Explain how early astronomers understand and describe the solar system

Explain why the solar system is arranged the way it is

Identify what is in the solar system besides planets

Explain how the moon formed Explain how astronomers know

about exoplanets

By understanding how things form, scientists can determine where other planets may be located, what they could be made of, etc.

Ancient people like the Greeks, Romans, and Druids, used stories to explain star movements

The first model of the solar system put Earth at the center. (kinda egocentric isnt it?)

Actually, its geocentric, in 140 CE Ptolemy expanded this model

Even though Ptolemy’s model was wrong, it was still used for over a thousand years

It wasn’t until 1543 when Nicolaus Copernicus proposed a heliocentric model of the solar system

In 1605 Johannes Kepler improved the model and made the orbits slightly elliptical, rather than circular

Isaac Newton was the first to explain that gravity keeps the planets in orbit around the sun and satellites in orbit around planets

Every object in the universe (having mass & proximity) exerts some kind of gravitational force on every other object

All of classical physics is built on this assumption

The Nebular Hypothesis

Scientists estimate the solar system to be roughly 4.6 billion years old

A nebula is a large cloud of dust and gas in space, the hypothesis explains why objects that form in a disk will lie in the same plane, and have almost circular orbits in the same direction.

Planets form by a process called accretion

It is basically the “sticking together” of particles in the disk

This also explains the difference in composition of the inner planets compared to the outer planets

See page 674 for a good view of the nebular hypothesis

Rocks in Space

Comets are small bodies of ice and cosmic dust that follows an elliptical orbit and gives off gas and dust in the form of a tail as it passes in front of the sun

Asteroids are large rocky bodies found mostly between Mars and Jupiter

Meteoroids are small pieces of rock that enter Earth’s atmosphere

Meteoroids do not contact the Earth’s surface, if they do they are called meteorites

Comets give glues to the origin of the solar system

Comets are composed of dust and ice made from methane, ammonia, carbon dioxide, and water

Some comets contain silicon, magnesium, and iron

Comets are sometimes called dirty snowballs Comets have tails when they come close to

the sun

During the formation of our solar system, some leftovers didn’t combine

The Oort Cloud is where comets tend to reside The Oort Cloud may be up to 100,000 AU

wide Halley’s Comet is one of the most famous it

travels an eliptical orbit and appears in Earth’s sky every 76 years

It will appear again August 20th 2061 and will pass within .05 AU of Venus

In 2134 Halley’s comet will pass closer than .1 AU of Earth

Meteorites can be made up of many types of elements

There are three major types of meteorites1. Stony2. Iron3 Stony iron Meteoroids sometimes strike earth Objects smaller than 10m probably burn

up in the atmosphere

Large meteorites can explain some mass extinctions and climate changes

The extinction of the dinosaurs is theorized to have happened by a meteorite roughly 10-15km wide

The moon formed from part of the earth A large celestial body collided with the

primordial earth The ejected material clumped together The gravity of the material pulled it into

a sphere The moon began to orbit the Earth

Do other stars have planets? Astronomers have discovered more than

200 exoplanets, or planetlike bodies that orbit other stars

Almost all of the exoplanets known have masses similar to Jupiter or Saturn

Homework: 679 1-7