Our Universe: Creation, Galaxies, Stars and Celestial Objects.
Stars Stars, Galaxies, and the Universe Ch 30 SOL 13 Objective ES 1 and 2.
-
Upload
derrick-burke -
Category
Documents
-
view
215 -
download
1
Transcript of Stars Stars, Galaxies, and the Universe Ch 30 SOL 13 Objective ES 1 and 2.
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
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!
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 farther to the red end.
Faster
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
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.
Gravitational force
Birth of a starBirth of a star
NebulaNebula
Pressure builds up and the core starts to heat up giving out infra red radiation.
Birth of a starBirth of a star
ProtostarProtostarStarStar
The gravity eventually gets so big and the temperature gets so high that nuclear fusion starts, it becomes 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
Radiation PressureFrom the energy of fusion
Gravitational forceFrom the mass of the material
A Stable Star like our SunA Stable Star like our Sun
Nuclear fusion4 Hydrogen 1Helium + ENERGYNuclear fusion4 Hydrogen 1Helium + ENERGY
The force of the radiation pressure from nuclear fusion is balanced with the gravitational force in a stable star.
StarStarRed GiantRed GiantWhite dwarfWhite dwarfBlack DwarfBlack Dwarf
Eventually a star the size of our sun becomes a Red Giant.
The star keeps increasing in size until the gravitational force causes it to collapse into itself creating a White Dwarf
This cools down to become a black 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
Large StarLarge StarRed
SupergiantRed
SupergiantSupernovaSupernovaNeutron StarNeutron StarPulsarPulsarBlack HoleBlack Hole
A larger star eventually becomes a super Red Giant.
This then collapses, heats up and explodes in a supernova.
The small core becomes a neutron star. 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.
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 ) andAzimuth ( 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
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
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
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.