Download Sun, Star Types and Luminosity

STAR TYPES AND LUMINOSITY
Definitions
 Sun: Star at the center of our solar
system. Also another name for any
star.
 Luminosity: measures how bright a
star would be in relation to the sun if
all stars were the same distance from
the observer
 Nuclear fusion: the combining of the
nuclei of smaller elements to form the
nuclei of larger elements with some
mass being converted into energythis is how the sun produces energy
 The color of a star is determined by
the temperature of the star- blue is
the hottest and red is the coolest
Definitions
 Sunspots: a darker region of
the sun’s visible surface;
increased number of sunspots
are related to an increase in
electromagnetic energy
emitted from the sun. Cycle is
about 11 years in length
Photosphere with Sun Spots
Stefan-Boltzmann Law
(Energy directly proportional to temperature)
 Our sun burns “slowly” 9 billion
years total (4.5 billions years left to
go!)
 Stefan-Boltzmann Chart: Organizes
stars by size, temperature and
luminosity
Development of Stars
 Stars may follow different paths in
this cycle
 Life cycle may take billions of years
 Some stars created soon after the Big
Bang may still exist
Nebula
a. a huge, spread out cloud of
gas and dust in space.
b. The gas in nebulae is
mostly hydrogen gas
c. Ingredients needed for star
formation
Main Sequence/Average Star
a. Main sequence stars are the central
band of stars on the star diagram.
b. Energy comes from nuclear fusion as
they convert Hydrogen to Helium.
c. The sun is a typical Main Sequence
star.
d. Most stars (about 90%) are Main
Sequence Stars.
e. For these stars, the hotter, the
brighter
Giant Stars
a. Rare red, orange, and yellow stars
commonly seen at night because of
their large size and high luminosity
b. Low temperature stars
c. Represent the late stage in the
evolution of medium to small-size main
sequence stars
Planetary Nebula
 nebula formed by a shell of gas
which was sent out from a certain
kind of a red giant or supergiant.
 As the giant star explodes, the
core of the star is exposed.
 Planetary nebulae have nothing
to do with planets.
White Dwarfs
a. Not always white
b. Small (around the size of Earth)
c. Hot on the surface, low in luminosity
d. Represent last stage of low to medium
mass stars
Black Dwarf
a. When a white dwarf cools and no
longer emits much electromagnetic
energy
b. “Dead” star
Other Path: Super Giants
a. Super giant stars can be up to 1000
times larger than the diameter of the
sun
b. Late stage of evolution
c. Usually explode in a supernova
d. Blue super giants are the brightest
and exhibit the highest temperature
Supernova
a. the explosion of most of the material
in a star, resulting in an extremely
bright, short-lived object that emits
vast amounts of energy.
b. Occurs when nuclear fuel is
exhausted so the star can no longer
support itself through fusion
Black Hole
 An area of space with a
gravitational field so intense
that its escape velocity is
equal to or exceeds the
speed of light- results from
supernova
Neutron Stars
 A celestial body consisting of
the dense remains of a massive
star that has collapsed, thus
leaving only neutrons, and
having a powerful gravitational
attraction
Movies
 Life Cycle of Stars
 Another Video of Life Cycle