Formation of the Solar System Chapter 19 Section 3

Astronomy – A history The first record of the study of astronomy was in Nabta, Egypt Group of stones were arranged to line up with the sun on the longest day of the year (summer solstice) Stonehenge, England – one of the world’s oldest observatories Stones are aligned with the winter and summer solstice

The Universe THE SUM OF ALL SPACE, MATTER, AND ENERGY THAT EXISTS, THAT HAS EXISTED IN THE PAST AND THAT WILL EXIST IN THE FUTURE. Inside of this universe there are galaxies that hold millions of stars. We are located in one of these galaxies…THE MILKY WAY GALAXY.

The Milky Way Galaxy

Models of the Earth History of the Universe Model The first models had the Earth in the center of the solar system – GEOCENTRIC Greeks were the first to try to determine Earth’s place in the universe Aristotle used math and models to illustrate the universe

Models of the Earth History of the Universe Model Copernicus was the first to put the sun in the center of the solar system (1543) – HELIOCENTRIC Also explained that the earth and other planets orbited the sun in perfect circles.

Models of the Earth History of the Universe Model Kepler (1605) – improved on the Copernicus model Explained that the orbits are actually ellipses or ovals At this time, there was no mathematical proof so it was not considered true.

Models of the Earth History of the Universe Model Newton (1687) – Explained Gravity Helped to explain why the planets traveled in elliptical orbits around the sun Explained that every object in the universe exerts a gravitational force on every other object.

Gravitational Forces Every object in the universe has a gravitational force. Larger objects have more gravitational pull compared to smaller objects. Smaller objects that are close enough to a larger object will ORBIT the larger object.

Formation of the Solar System The NEBULAR MODEL This is the most widely accepted model for the formation of the solar system (-p. 648-649) NEBULA – A large cloud of dust and gas in space…region where stars are born or explode According to this model the sun and planets formed from a cloud of gas and dust that collapsed because of gravity.

Steps in the Nebular Model 1. Young solar nebula collapses due to gravity. 2. Solar nebula begins to rotate, flatten, and get warmer near the center. 3. Small “planetismals” begin to form 4. Larger “planets” begin to collect dust and gas from the nebula 5. ACRETION – smaller planetismals collide with the larger “planets” causing them to grow 6. Remaining dust and gas are eventually removed…leaving planets around the sun 7. A NEW SOLAR SYSTEM IS FORMED!

The Big Bang Theory The theory that all matter and energy in the universe was compressed into an extremely small volume that 10 to 20 billion years ago exploded and began expanding in all directions.

Red Shift and Blue Shift The Doppler Effect Based on wavelengths of light. Longer wavelengths show red shift Shorter wavelengths are blue shift Red Shift relates to the movement of objects away from the observer (our universe has red shift so it is believed to be expanding) Blue shift relates to the movement of objects towards the observer

Galaxies Contain millions to billions of stars Distances between galaxies are extremely large. 3 Types of Galaxies – Spiral, Elliptical, and Irregular

Spiral Galaxies Have spiral arms made of gas, dust, and stars. Example: Milky Way Galaxy

Elliptical Galaxies Have no spiral arms and are egg shaped. They contain mostly older stars.

Irregular Galaxies Lack regular shapes and do not have a well-defined structure

Stars: Life and Death Chapter 20

Stars A large celestial body that is composed of gas and emits light The SUN is a typical star that is just closer to earth than other stars The Greeks grouped stars into shapes called constellations Core temperature is more than 15 million Kelvins

Nuclear Fusion in Stars Takes place in the core of the star Combines Hydrogen atoms fusing together because of high temperature and pressure Energy from fusion is released as radiation and convection through the star layers Light travels at 3 x 108 m/s From the sun to the earth it takes 8 minutes

Brightness Depends on the star’s temperature and distance from earth Sirius – brightest star in the night sky

Star Color Related to its temperature Hotter objects glow brighter and have shorter wavelengths (closer to blue) Cooler objects have less intense color and have longer wavelengths (closer to reds) The sun appears yellow because the peak wavelength of the sun is near the color yellow …Yellow also corresponds to a temperature near 6000 kelvin

The Life Cycle of a Star Stars appear different when they are in different stages of the life cycle Stars are born, they develop, and they die Stars are “born” from a NEBULA (cloud of gas and dust) The SUN is thought to be in middle age and has about 5 BILLION years left in it.

Star Life Cycle Low Mass/Medium Mass Star Nebula Protostar Star Red Giant Planetary Nebula White dwarf Black dwarf High Mass Star Nebula Protostar Star Super Giant Super Nova Neutron star or Black hole

A Star is Born Stars are formed from a Nebula collapsing inward and spinning faster and faster. The center core increases in temperature Nuclear forces begin the process of fusion And the star is turned on

A Dying Star Fusion begins to slow down, pressure in the core drops and the core will contract…causing core temperature to rise. RED GIANT – A large reddish star late in its life cycle WHITE DWARF – a small, hot, dim star that is the leftover center of an old star No longer fuses elements Most stars in our galaxy end as white dwarfs

SuperGiant Stars Massive stars that evolve faster than smaller stars Develop hotter cores…create heavier elements through fusion Fuses Iron atoms right before its death When fusion stops, the core collapses and causes a shock wave … and causes a bright explosion.

SuperNova A gigantic explosion from the collapsing of a massive star Supernova explosions cause NEUTRON STARS or BLACK HOLES

Neutron Star

Black Hole An object so massive and dense that not even light can escape its gravity Since no light can escape a black hole cannot be seen directly They have a very strong gravitational pull.

Hertzsprung-Russell Diagram P. 673 shows an example Helps astronomers understand how stars change over time Vertical axis indicates brightness Horizontal axis indicates surface temperature of the star When stars are born, they appear as protostars Position of a star changes as they go through their life cycle Red giants are cool and bright so they are in the upper right White dwarfs are faint and hot so they are in the lower left.