Download Nuclear Fusion – when two H atoms combine to form one atom thus

STAR NOTES
Stars – stars are burning balls of gases. Result of nuclear explosion called nuclear fusion
Nuclear Fusion – H is converted to He. Two H atoms combine to form one atom of He thus releasing
huge amounts of energy in the form of heat and light.
Fission – the splitting of a H atom
Gravity – force of attraction. Causes H atoms to collide and combine. Cause of nuclear reaction
Nebula – Stars are formed or “born” in a nebula. Massive cosmic cloud of matter from
which stars are created.
Light Year – distance light travels in one year. 186,000 miles/sec – speed of light
Life Cycle of a Star
Stars start off as a nebula until a nuclear explosion causes the star to shine. The newborn star is called a
protostar. As the protostar moves into the main sequence of its life, it grows larger. The star will
eventually become a red giant or super red giant. This occurs in every star. Based on the amount of mass
a star begins with, it will either wind up as a black dwarf, a neutron star or a black hole. The amount of
mass a star begins with will determine how it will evolve and how long it will exist.
5 Characteristics of a Star
1.
2.
3.
4.
5.
size
composition
color & temperature
brightness
distance
Size – there are five sizes of stars
Neutrons – 16 km. in diameter
White dwarf – ½ the diameter of Earth
Medium – the sun. 109 times size of earth.
Giant – 10 to 100 times the size of our sun
Super Giant – 100 to 1000 times the size of our sun
Composition
Stars are composed of gases
H 60 – 80 %
He 19 – 39%
99% of a star is made up of H and He
The composition of a star is determined by using a spectroscope.
Spectroscope – an instrument which breaks light into its spectrum of colors (ROY G BIV)
When an element burns, its light produces a characteristic set of lines when viewed
through a spectroscope. These lines are like fingerprints which identify the burning
element
Color & Temperature
Color
Temperature
Red
Orange
Yellow
White
Blue/bluish white
3000C
5000C
6000C
10,000C
35,000C
Brightness
The measure of a star’s brightness is called its magnitude
Apparent Magnitude – how bright a star appears from earth.
Absolute Magnitude – the actual amount of light a star gives off
H-R Diagram - A graph that shows the relationship between a star's absolute magnitude and its
temperature
Distance
There are three methods to determining the distance of a star
1. Parallax – uses the movement of the Earth around the sun to calculate the distance of a star.
Reliable for stars up to 100 light years away
2. Brightness – uses apparent and absolute magnitude to determine the distance of a star.
Reliable for stars up to 7 million light years away
3. Spectroscope – measures the amount of red shift in a star's spectrum
DOPPLER EFFECT
Doppler Effect – the apparent change in the wavelength of light that occurs when an object is moving
towards or away from earth.
Red Shift – Stars moving away from earth will have wavelengths in the red area (Long Wavelengths) of
the spectrum. The
RED…DANGER…AWAY
Blue Shift – Stars moving toward earth will have wavelengths in the blue area (Short Wavelengths) of the
spectrum.
BLUE…WATER…TOWARDS
Universe – space and all the objects in space. 15 – 20 billion years. old
The Big Bang Theory – States that all of the matter in the universe was once all together. A nuclear
explosion caused the matter to be hurled outward in all directions. The
universe is still moving outward in all directions. Still expanding.
Gravity caused much of the matter to combine together forming the galaxies we now see.
Although there are billions upon billions of stars in the universe, most of the universe is mainly empty
space.
Background Radiation – Energy which was left over after the nuclear explosion of the big bang. This
energy is spread evenly throughout the universe. Provides evidence supporting
the big bang theory.
Two theories of the universe
Open theory - The universe will continue to expand until all of the energy is used and the universe dies.
Closed theory - The universe will continue to expand until the force of gravity causes the matter to reform
thus starting the process over again
Galaxies - huge collection of stars
Three types of galaxies
Ellipitical - egg or football shaped
Spiral - pin wheel shaped (milky way)
Irregular - no defined shape
Star Systems
Single star system - only one star (sun)
Binary star systems - two stars which revolve around each other.
Multiple star system - three or more stars which revolve around each other.
Eclipsing binary - when a dim star blocks the light of its brighter companion star. (Algol)
Nova - A star which becomes extremely bright for a few weeks before returning to its normal brightness.
Can only occur in binary stars. When gases from a star strike a companion star causing it to become very
bright. (lighter fluid on flame).
Milky way - our galaxy, 200 billion stars