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Galaxies
A galaxy is the basic structural unit of matter
in the universe.
A galaxy is a collection of stars (usually 100 billion or more), gases and dust held together by gravity. It is believed that
the universe is made up up of more than 100 billion galaxies.
Galaxies are classified by their shape: elliptical, irregular or spiral.The Milky Way Galaxy
is spiral-shaped.
Stars and their Energy Production
A star is the most visible piece of matter in a galaxy; it is a large ball of gas that produces a
large amount of energy. This ball of gas is held together by gravity.
Most of the energy produced by a star is a result of nuclear fusion. Nuclear
fusion is the combining of smaller elements to make larger one. In this
process, some of the mass is converted into energy.
In our sun, hydrogen nuclei is converted into helium. Less than 1% of
this mass is converted to energy.
Nuclear fusion requires a tremendous amount of heat and pressure.
The energy from the sun (through nuclear fusion) is radiated into space in the form of electromagnetic radiation.
In our sun, hydrogen is combined to make
helium.
Characteristics of Stars
RT = Pg. 15
The chart shown is a tool used by scientists to make comparisons between stars
based on their surface temperature and luminosity.
Luminosity is the rate at which a star emits energy
with relation to our sun if all stars were the same distance
from an observer.
The chart shows a pattern between the surface
temperature of a star and its luminosity.
As a star “cools”, the color of the star will change.
Star TypesRT = Pg. 15
Main Sequence1. Most of a star’s life span is
in main sequence.2. Average size
Giants1. 10X larger or more than the
sun2. Red, orange, yellow in color
Super Giants1. Very Bright!2. 100-1000x larger than the
sun.3. End stage of star
development; usually followed by a supernova.
White Dwarfs1. Very small (Earth-sized)2. Very hot; not so bright!3. End stage of star
development; usually followed by a black dwarf
Star Origin and EvolutionGas and dust Matter originates from “Big Bang”.
Matter collects, gravity forms and nuclear fusion begins
Main Sequence Star
Red Giant forms
White dwarf forms as fuel is used up.“Death” of a
star; Black dwarf
Super Giant forms
Neutron star forms; very dense
Black hole forms; extreme gravity field created
Supernova!
Star Evolution for
stars of similar mass
to that of the Sun.
Star Evolution for stars more massive than the Sun.