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.
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
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
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.
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.
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
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