A star is a massive sphere of gases with a core like a thermonuclear reactor.

They are the most common celestial bodies in the universe are stars.

They radiate energy (electromagnetic radiation) from a hot core

It is estimated there are more stars in the universe than there are grains of sand on all the beaches on Earth.

See pages 368 - 369

Space is filled with the stuff to make stars.

Interstellar matter Means ‘’ between the stars’’. Describes the regions of space between stars. By peering through the interstellar matter (dust and gases), astronomers can observe the birth of stars.

The formation of Stars

Stars are formed from massive clouds of dust and gas in space

Gravity pulls the dust and gas together

As the mass falls together it gets hot.

A star is formed when it is hot enough for a nuclear reaction to start - the hydrogen nuclei fuse together to make helium.

This releases energy which keeps the core of the star hot.

The Sun is halfway

through its 10 billion

year stable phase

During this stable phase in the life of a star, the force of gravity holding the star together is balanced by the high pressure due to the high temperatures.

Our Sun is at this stable phase in its life.

Nebula

(dust & gas)

Gravity pulls dust & gas together

Mass grows

•Material collapses in on itself •contracts

Protostar

(early star)

Small mass

collected

Shrinks

away

Enough gas

& dust

collected

Core reaches

10 000 000 0°C

At that point…

Atoms fuse together (Hydrogen atoms combine to form heavier helium atoms)

NUCLEAR FUSION REACTION

ENERGY!!!! c

A Star is Born

http://www.youtube.com/watch?v=MGalnuFS2

O0&feature=related

Figure 11.3 – 3 main life paths of stars

The Evolution of Stars Stars do not stay the same forever, and their future depends on how

much mass they have.

Classification Characteristics Speed of burning fuel

Life time

(years)

What happens to them?

Low Mass

Star

•Dim

•Cool

•Red dwarf

Very slow

100

Billion

years

Eventually change into

very hot, small, dim

white dwarfs

Summary : Red dwarf white dwarf

Low Mass Stars

Intermediate Mass Stars

Classification Characteristics Speed of burning fuel

Life time

(years)

What happens to them?

•Intermediate Mass Star

•Similar to

our Sun

Expands to a

Red Giant

Our sun will

expand to a red

giant in about 5

billion years

Fast

10

Billion

years

•Collapses in on

itself

•Shrinks to form a

white dwarf

•Then cools to

become a Black

dwarf (dense, dark

body made mostly

of carbon and

oxygen)

Summary Red giant white dwarf black dwarf

A white dwarf star compared to Earth

High Mass Stars

Classification Characteristics Speed of burning fuel

Life time

(years)

What happens to them?

High Mass

Star

•12 or more

times the

mass of our

Sun)

•Expands

to a Red

Giant

•Very fast

Due to rapid

growth and

large

size

7

billion

years

•Uses up all energy

& becomes a

supergiant

•Collapse in on

themselves

•causing dramatic

explosion called a

supernova

Summary Red giant super giant neutron star

Neutron stars

The explosion from a star forming a supernova throws dust and gas into space which may eventually form parts of a new stars. The material left behind after the explosion forms a very dense type of star, called a neutron star (much denser than a white dwarf)

Black holes The remnants of a supernova may form a neutron star;

however, if enough matter is left behind, it may contract

under its own gravity to become extremely dense.

With such a strong gravitational field that nothing can

escape from it, not even light

Questions

Why are supernovas so important to us?

What is a neutron star? What evidence is there for the existence of black holes?

•Workbook pages 154 &157

Look at the diagram…..

It shows a Star Cluster

What are 3 observations you can make?

•size •color

•brightness

•temperature

Made observations about Stars

Both concluded stars do not stay the same forever

Stars do not exist in all sizes, luminosities, or temperatures.

What did they observe?

1. Luminosity (brightness) Dim Bright

Possible scale

2. Color Bluer Redder

3. Temperature Hotter Cooler

This information was plotted on a graph known as the Hertzsprung-Russell Diagram

See page 374

3. dwarf stars.

1. giants (sometimes subdivided into giants and supergiants),

It shows that stars are found in three main categories:

2. main sequence, and

There are a few "Red Giants", or "Blue Super giants",

Finally… there are a few very faint stars near the bottom left of the diagram - these are the white dwarfs.

Astronomers reasoned that if a star were hotter, it should have a higher luminosity, and a cooler star would be dimmer. As it turns out, most stars, (90%) fit this pattern. They can be found on the HR diagram in the large group that stretches across the middle of the diagram. These are called the Main Sequence Stars

The colour of a star reveals its temperature and chemical composition to astronomers. ◦ Red stars = cool = 3000 ºC Yellow stars = hot = 6000 ºC Blue stars = hottest = 20 000 ºC - 35 000 ºC

See pages 374 - 375

Using a spectroscope, the light emitting from a star reveals spectral bands that show certain gases in the star as different elements have different spectral patterns Of course, spectral lines are also used to

identify the movement of stars by utilizing red-shift analysis.

Red-shift is an example of the Doppler effect, which states that as a wave-emitting object moves, the wavelength of its waves change.

Analyzing Spectral Patterns

1. (a) Mystery star 1: hydrogen and helium

(b) Mystery star 2: hydrogen, helium, and sodium

(c) Mystery star 3: hydrogen and calcium

2. (a) Mystery star 4: hydrogen

(b) It is red-shifted.

Light (and sound) energy travels in waves

The wavelength changes due to motion Diagrams on board

The Doppler effect refers to the way waves either compress as their source gets closer, or lengthen as the source gets farther away. ◦ The unique spectral pattern each star reveals when

examined through a spectroscope allows astronomers to see if the lines shift towards the red part of the spectrum (moving away) or blue (moving closer).

See pages 376 - 377

A planet is a celestial body that orbits one or more stars ◦ Large enough that gravity holds it in a spherical

shape

◦ Is the only body occupying the orbital path

◦ Only reflects light radiated by its star (does not generate its own light)

A solar system is a group of planets circling one or more stars ◦ Our sun formed 4.5 billion years ago

Not all planets formed at the same time

Material closest to the Sun formed first

◦ Called the inner or terrestrial planet ◦ = Mercury, Venus, Earth, Mars

Solid cores & rocky crusts

Farther away, large clumps or gas, ice, and dust formed the outer or Jovian planets ◦ Jupiter, Saturn, Uranus, Neptune

Large, gaseous bands & cold

My

Very

Educated

Mother

Just

Served

Us

Nachos

Mercury

Venus

Earth

Mars

Jupiter

Saturn

Uranus

Neptune

Earth’s rotation around its “axis” at speed of 1670 km/h or 0.5 km/sec

Earth’s revolution is around the sun (elliptical orbit) at 30 km/sec

110 Earth’s to fit across the sun’s diameter

Mostly hydrogen gas – fusion reactions (H + H = He) produces the Sun’s energy (heat & light)

Complete “The Sun” worksheet labelling and defining terms

Sudden bursts of hot gases from the sun’s corona

Rush past the Earth & cause solar winds ◦ Cause Northern/Southern lights at poles when

these particles are deflected from Earth’s magnetic field

◦ Thankfully as they would be fatal otherwise

an aurora hovering over the southern Indian Ocean (May, 2010)

Moons ◦ Orbit the planets

◦ Over 150 moons detected in our solar system

◦ Mercury & Venus do not have a moon

Asteroids ◦ Small, left over from formation of solar system

◦ Asteroid belt = huge band of asteroids orbiting the Sun

Comets ◦ Made of ice, rock & gas from Kuiper Belt & Oort Cloud

◦ Hurtle through space and when they feel the effects of sunlight, we see its trail of gas & dust

◦ Therefore tail will always point away from the Sun

Trans-Neptunian objects ◦ Objects that circle the sun beyond Neptune such as

the Kuiper Belt (made of millions of small bodies)

◦ Contains dwarf planets (Pluto)

There may be 23 potential planets orbiting in Kuiper Belt

Oort Cloud ◦ Outermost edge of Sun’s gravitational influence

◦ Spherical cloud of small, icy fragments of debris

◦ Between 50,000 & 100,000 AU (Astronomical Units) away from the Sun