Galaxies• The basic structural unit of matter in the
universe is the galaxy• A galaxy is a collection of billions of
_____________ , gas, and dust held together by ____________________
• An average galaxy will have over ___________________________ stars
starsgravity100 billion
Galaxies• Galaxies are classified by their shape• The three most common shapes are:– ________________________ (football shaped)– ________________________– ________________________**based on the speed at which they rotate
EllipticalIrregularSpiral
Milky Way Galaxy
• Our solar system is part of a ________________ galaxy called the Milky Way Galaxy
• The Milky Way galaxy has about _________ billion stars
• It is rotating very ___________
spiral200
fast
Milky Way Galaxy2 main spiral
“arms”
Stars
•https://www.youtube.com/watch?v=5az0W4Y1nuU
Stars• The majority of the visible matter in the
universe is made up of gas clouds, dust, and ____________
• Definition:– A star is a large ball of __________ held together by
gravity– Stars produce tremendous amount of
________________ and shine
starsgas
energy
Stars• The majority of the visible matter in the
universe is made up of gas clouds, dust, and ____________
• Definition:– A star is a large ball of __________ held together by
gravity– Stars produce tremendous amount of
________________ and shine
starsgas
energy
Sun• The star associated with the Earth and the
rest of our Solar System is called the ________• The Sun is the main gravitational ____________
holding the Solar System together• Most stars have a solar system revolving
around it
Sunforce
Energy in Stars
• Stars produce a tremendous amount of energy!
• Stars create energy as a result of nuclear fusion in their ___________cores
Nuclear Fusion• Nuclear Fusion is the process of combining
the nuclei of two ____________________________ to create an atom with one larger nuclei
smaller atoms
v
Nuclear Fusion• What is a nucleus?– Dense region at the center of an atom that
consists of _______________ and __________________
• Let’s look at an atom of Hydrogen!protons neutrons
Nuclear Fusion• Below is an atom of Hydrogen:
How many protons are in the nucleus?
1!
Nuclear Fusion• During Nuclear Fusion, two Hydrogen atoms
will be combined to form an atom with 2 protons in its nucleus
+ =
Nuclear Fusion• During the combination of nuclei, some of
the ____________ left over is converted into _________________
• Our Sun converts hydrogen nuclei into helium nuclei similar to the example
massenergy
Nuclear Fusion• Nuclear Fusion can only occur in extremely
high ________________________ and high ____________________ conditions
temperaturepressure
• http://www.bing.com/videos/search?q=nuclear+fusion+in+stars+youtube&qpvt=nuclear+fusion+in+stars+youtube&FORM=VDRE#view=detail&mid=97FD5A55FA8317BCF55597FD5A55FA8317BCF555
Star Classification• Stars are classified by two main conditions:
1. Surface Temperature2. Luminosity
Surface Temperature• The differences of surface temperature of
stars is reflected by their ______________
Think about a candle flame, the hottest part is the closest to the wick – which is blue!
The same pattern can be seen with stars. The hotter the star, the bluer it appears. Less hot stars are more yellow/orange.
color
Luminosity• Luminosity is the ___________________ of a star• However, when we observe distant stars
from Earth, we are seeing its apparent brightness, not its luminosity
• The farther the star is away from us, the __________ bright it will appear
brightness
less
Characteristics of Stars
• Reference Table – Page 15!• Characteristics of Stars
1. Look at the X axis, what is the variable? What is it measured in?
2. Look at the Y axis, what is the variable? 3. As you increase along the X axis, what
happens to temperature?
Characteristics of Stars
4. Which star is more luminous – Alpha Centauri or Rigel?5. Which star has a higher surface temperature – Spica or Polaris?6. Read what’s in the parenthesis under
Luminosity – explain why this is so.7. Find Polaris on the table. Does it have a high
luminosity? Is this what you would have expected?
Characteristics of Stars
8. What is the approximate color of Procyon B?
9. Is there any relationship between luminosity and color of the star?
Star Types• There are 5 main types of stars:– Main Sequence Stars– Giant Stars– Super Giants– White Dwarfs– Black Dwarfs
Main Sequence• About 90% of all stars are Main Sequence stars• Main Sequence stars are generally average
_____________• For all Main Sequence stars, as surface
temperature starts to increase, luminosity also _________________
• Most stars spend the majority of their life as Main Sequence stars
size
increases
Main Sequence• The increase in luminosity that Main
Sequence stars go through is a result of its increasing ________________________
• Our Sun is a Main Sequence star of ____________ color
temperatureyellow
Giant Stars• Giant Stars are often referred to as “The Red
Giants” because of their _________________________________ coloring
• These stars are extremely large! (about 10x the diameter of the Sun)
• They have an extremely high __________________ but a low temperature
red and orange
luminosity
Super Giants• Super Giant Stars can be anywhere from 100
to __________ times the diameter of the Sun!• These stars are extremely luminous • Super Giants usually explode in a tremendous
event called a _______________________• In order for a star to eventually become a
Super Giant, it must have started out much larger than the Sun
supernova
1000
White Dwarfs• White Dwarfs are _____________!• They are usually about the size of the Earth• White Dwarfs can be anywhere from white
to _________ in color• They are very hot but ________ in luminosity• Represent the last luminous stage of a star
small
lowblue
Black Dwarfs• When a White Dwarf cools and no longer
emits any ______________-, it is considered a “dead” star – or a Black Dwarf
• These stars have stopped nuclear fusion and no longer produce any nuclear energy
• They are extremely ____________
energy
dense
Life of a Star• https://www.youtube.com/watch?v=PM9CQDlQI0A
Life Cycle of Stars• Stars, like many objects on Earth, have a
beginning, an _________________ of features, and an ending
• Just like us, stars are ___________
evolution“born”
Star Birth• Stars originate from clouds of __________ and
gas molecules• These star forming clouds are called
__________________
dust
nebulas
Nebulas• Nebulas were created from the masses of
_________________ that were released during the Big Bang
• Eventually, some of the gas and dust particles in a nebula will begin to _____________ together
• As these clumps gain more mass, they build up a stronger __________________________ pull that causes more and more matter to be sucked into it
matter
clumpgravitational
Nebulas• Once this mass gains enough size (reaches
about the size of Jupiter), the gravitational pull results in high enough _____________________ and ___________________ to start nuclear fusion!
• The ball then begins to _____________ as it radiates energy --- thus, a star is born!
temperaturepressure
shine
Nebulas
Main Sequence• Every star begins its journey on the Main
Sequence after it is created in a nebula• All stars spend most of their lives as a Main
Sequence star• These stars will range greatly in their
__________,which will affect the rest of their livesmass
Smaller Stars• Stars with a mass similar to our Sun and
smaller will spend billions of years as a Main Sequence star and eventually will become a _____________________
• As these stars age, they get ______________ and more ___________________
Red Gianthotter
luminous
Smaller Stars• After billions of years, these stars eventually
use up most of their nuclear fuel used for ____________ and collapse to form a __________________________
• They will then slowly die as they run out of nuclear fuel completely and become a ________________________
fusionWhite DwarfBlack Dwarf
Smaller Stars• These Black Dwarfs are extremely ____________
and have a very strong gravitational pull• However, they no longer emit any __________
because nuclear fusion has stopped
denselight
Smaller StarsGas and
dust cloud - Nebula
Main Sequence Star Red Giant
Red Super Giant
White Dwarf
Black Dwarf
Larger Stars• Larger stars are any star that is ________times
the mass of our Sun• These stars exist for much _______________
periods of time (approximately 100 million years)
• These stars start as very ___________ Main Sequence stars
1.5shorter
large
Larger Stars• Next, they become _________________________• They eventually ___________________ in an event
called a Supernova
Super Giantsexplode
Larger Stars• A supernova is a stellar __________________• When nuclear fusion no longer takes place in
the stars core, the core _________________ and releases a huge about of energy
• A Supernova will occur about once every 50 years in a galaxy the size of the Milky Way – which means they occur about every second in the universe!
explosioncollapses
Larger Stars• During a Supernova, the star _____________
collapses, forming a mass much smaller than a White Dwarf
• They get so small and ____________ that only neutrons can exist – these are called _________________________
rapidly
denseNeutron Stars
Larger StarsGas and
dust cloud - Nebula
Main Sequence Star
Red Super Giant
Supernova
Neutron Star
HUGE Stars• When the most massive stars collapse, the
______________ is so large that an extreme gravity field is created
• No ____________ or any form of energy can escape
• This is called a _____________________
densitylight
Black Hole