Download Stars - PAMS-Doyle

Stars
Stars, Galaxies, and the Universe
Ch 30
SOL 13
Objective ES 1 and 2
What is a Star?
• A ball of energy that gives off a massive
amount of electromagnetic energy
Stars Spectrum
• These can tell you the
stars composition and
temperature
Spectra of Stars
• Stars are assigned spectral types of O,B,
A, F, G, K, and M which are based on
their temperature
• Each type is subdivided into the
numbers 0-9
• Provide information about the stars
composition and temperature
Apparent Motion
Motion of Stars
• They rotate on an axis
• They may revolve around another star
• They move toward or away from our solar
system.
• The Doppler Effect can determine their
direction…works just like sound in the
apparent shift because of motion!
The same shifting happens with the
light from a moving star.
Lower Frequency
Higher Frequency
The spectrum of hydrogen that is
from a stationary source.
When the star is moving
closer...
Stationary Hydrogen
“Blue Shifted” Hydrogen from star
moving towards Earth.
And when a star moves away
from us...
Stationary Hydrogen
Lines are shifted to the red end.
And when a star moves away from
Faster
us...
Stationary Hydrogen
Lines are shifted farther to the red end.
Since the universe is
expanding...
• All distant objects have a red shift.
• The farther the object, the more extreme the red shift
Astronomers use this relationship
between distance and speed to measure
the distance to distant stars and galaxies.
• .
Positions and Distances of Stars
• Distance is
measured in light
years
• 9,461,000,000,000
km in one year
• To account for the
motion of the Earth
when viewing the
stars, the apparent
shift in position of
the star is called
parallax
Measurements
• Distances to the closest stars can be
determined through measurement of the
trigonometric parallax. The parsec is
defined to be the distance at which1AU
subtends an angle of 1 arc second.
Stellar Brightness
• Apparent Magnitude:
the brightness of a star
as seen from Earth,
does not take into
account the distance.
• Absolute Magnitude:
the actual brightness of
a star
Hertzsprung-Russell diagram
• The properties of mass, luminosity (total
energy output), temperature, and diameter
are closely related
• Each star has specific characteristics
related to each of the properties
• 90% of all stars fall along main sequence
http://lcogt.net/en/book/stages-stars-life
Stellar evolution
• Mass and composition determine nearly all
of a star’s properties.
• Fusion occurs to generate the energy from
the star
• Not only can Hydrogen be fused to make
helium, other elements can also be made
He into C, C + He to make O, then Ne, then
Mg, then Si.
Birth of a Star
All stars start life as a nebula of gas and
dust. Over millions of years gravity pulls
these closer together.
Birth of a star
Pressure builds up and the
core starts to heat up giving
out infra red radiation.
Gravitational force
Nebula
Birth of a star
The dust and gas from the
nebula is added to the
protostar, it gains mass. As
mass is gained gravity
increases and the
temperature within the
protostar increases
Protostar
Star
The gravity eventually
gets so big and the
temperature gets so high
that nuclear fusion starts,
it becomes a star
Life of a star
A Stable Star like our Sun
Gravitational force
From the mass of the
material
The force of the
radiation
pressure from
nuclear fusion is
balanced with the
gravitational
force in a stable
star.
Radiation Pressure
From the energy of fusion
Nuclear fusion
4 Hydrogen
1Helium + ENERGY
Death of a Star
Star like our Sun
A large Star
RedStar
Giant
Black
Dwarf
White
dwarf
Eventually a star the size
of our sun becomes a
Red Giant.
This cools down to
become a black dwarf.
The star keeps increasing
in size until the
gravitational force causes
it to collapse into itself
creating a White Dwarf
Life Cycle of a Star: Small and
Medium Stars
• Protostar
• Medium sized star becomes a red giant then
a white dwarf then become black dwarfs
Red
Pulsar
Large
Star
Supernova
Neutron
Black
Hole
Star
Supergiant
A larger star eventually
becomes a super Red
Giant.
The small core becomes
a neutron star.
This then collapses,
heats up and explodes
in a supernova.
This can turn into
a pulsar
If a star is large enough
it’ll become a black hole.
Massive Stars
• Massive stars can become a supernova and
blow up, its core can become a neutron star or a
Black hole
Ultra-Massive Black Holes
• Researchers theorized the potentially
ultra-massive black holes, which lie in
galaxies at the centers of massive galaxy
clusters containing huge amounts of hot
gas, may generate the energy outbursts
that keep this hot gas from cooling and
forming huge numbers of stars.
The larger the star the more fusion
can take place and form many
elements
Closest Star to Earth:
Alpha Centauri
Groups of Stars
• There are 88 constellations that were named
by ancient people
• They appear to move around the poles
• They can be seen only during
certain times of the year.
They are not gravitationally
bound together
Dividing the Sky
Zenith ( Position directly Overhead ) and
Azimuth ( Angle from North along the Horizon )
Binaries and Novas
• Two stars that are
gravitationally bound
together
• Orbit a common center
of mass
• Most appear as a single
star
• Star Clusters- spherical
arrangements of
hundreds of thousands
of stars
Galaxies
• Large gathering of stars, gas, and dust that
is bound together gravitationally.
Types of Galaxies
• Spiral Galaxies: Spiral shaped with
normal spirals and barred spirals
• Elliptical Galaxies: not flattened into
a disk shape, no arms, similar to a
football in shape
• Irregular Galaxies: no distinct shape
• Most galaxies are located in groups
rather than being spread throughout
the universe
Galaxy types
Elliptical
Spiral
Irregular
Milky Way Galaxy
• Side angle looks like a fried egg, flat
edges and bulging in the middle
• Spiral shape with arms rotating off
the sides, circulates around the
center bulge
• Center of galaxy has a high
concentration of stars
• Our solar system is located in the
arm of Orion
Quasars
• Most distant objects in the universe, they
give off a tremendous amount of energy
• May be related to black holes
• Stands for quasi-stellar radio source
COSMOLOGY
• The study of the universe, its nature, its
origin and its evolution
Big Bang Theory
• All matter and energy was compressed
into a small volume.
• About 14 billion years ago it expanded and
has been expanding ever since
• Support: The Red Shift of Galaxies and
Cosmic Background Radiation (low level
energy that formed shortly after the BB)
Dark Matter
• Dark matter and energy accounts for
96% of the mass in the universe, it is
invisible
• This is what makes the sky dark, it
does not give off, reflect or absorb
any light
Dark Energy
• Nothing is really known about dark energy
• Hypothesized to oppose gravity
• Force that is pushing galaxies away from
each other.
Will we ever travel to other
Galaxies?
• The nearest galaxy to ours is called the
"Sagittarius Dwarf" and it is about 60 000
light years away from our own galaxy (the
Milky Way). Assuming we can get a vehicle
to reach the speed of light, it would take 60
000 years for a vehicle to travel to this
galaxy.
• Given current technology, it is unlikely that
we will ever visit another galaxy.
Twinkle Twinkle