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To study for this test that has A TON of material


The study of the structure and evolution of the Cosmos from begining to end



Universe is


Percentage of space the galaxies take up


Cosmology asks

How did the Universe start?
When did the univverse start?
How do galaxies start and end?
How will the universe end?
When will the universe end?

Astronomers and Cosmologist use

The telescope

The telescope does not


How do telescopes work?

Collect and focus light to make faint objects visible to our eyes


Computer attachments to telescopes that analyze light. they cana determine the chemical composition of starts as well as their mass, temperature, and velocities

Emmission Spectra

spectograms for analysis, useful for determining what a star is made of/burning. Also temperature, mamss luminosit, redshift or blueshift and how long it will live

Light Year

Main unit of distance for cosmologists and astronomers. The distance that light can travel in a year.

Electromagnetic Spectrum

Longer wavelenth, lower frequency, lower energy to shorter wavelength, higher frequency, higher energy:
Radio, Microwave, IR (infared), Visible, UV (Ultraviolet) Xray, Gamma

Doppler Effect

This applies to photons of light as well as sound. Redshift and Blueshift


Apparent lengthening of light waves from light sources moving away


Apparent lengthening of light waves from light sources moving closer.

The key to our study of the universe


Looking at old light is like

looking back in time

Big Bang Theory

Current and best-working explanation of Universal origin developed in the 1920s by a catholic preist, it has stood the test of time with three main sources of proof.

The universe began at time


Universe began as a


The original object had

near-infinite mass and mear-infinite heat energy near-infinitely small volume infinite density

Our universe is

expanding and cooling

Firecracker analogy

too much energy being contained in a too small volume, it has to release the energy and cool down via expansion

Flaws in the theory of the big bang

fails to acount for the currently evolving universe with clusters of galaxies. the presecnce of these glaxies implies that the Big Bang reaction was imperfectly balanced for some reason

How old is our universe?

13.7 B years old

What is the average temerature of the universe?

3 degrees kelvin

We have no way of

"knowing the mind of god"

Hubble's theory

He observed that the majority of galaxies are moving away from us. He hypothesized that if everything did start out in the same place, and is now far away and is still moving away very fast, there must have been a large release of energy that started this expansion, a big bang!

Redshifted Cosmin radiation theory

If a big bang occured it would have required alot of heat energy. As the universe expands, the heat would spread out and the average heat of the universe would drop. Alpher and Gamov predicted that a universe that started with a big bang would have left over heat in the microwave range after 14 B yeaars. Penzias and Wilson discoverd a universal background temp. of 3k...which is in the microwave range.

H:He Ratio theory( predicted by Weinburg)

Weinburg did his calculations with the assumtion that the big band occured. His calculations yealded some conclusions that could be checked for accuracy. One of his conclusions was that a universe started by a big bang would be 74% H and 26% He. Using a Spectograph, we found that those assumptions were correct, with 1% other


Gravitationally bound collections of stars, gas and dust

The information awe have about galaxies is courtesy of

radio astronomy

radio waves

Only type of light with wavelengths long enough to travel great distances without significant distortion

3 main shaped of galaxies

spiral, eliptocal, irregular

what is in the center of our galazy?

a long dormant black hole

how many galaxies our in our locala group?



the closest galaxy to ours

how long will it take for us to collide with andromeda?

5b years

Star Birth, life and death are all based on

mass and the force of gravity

Step 1 of star life

Start with a nebula (a large cloud of gas and dust inside a galaxy)

Step 2 of start life

The large cloud is hit by a density enhancement event such as a shockwave from a start being born, a shockwave from an old star dying, two clouds colliding

Step 3 of start life

The more dense nebula collapses on itself and fragments into several smaller clouds

Step 4 of star life

Inside each small cloud, gravity pulls all the gas and dust towards their centers. aas things fall, PE turns to KE and: friction. Enormous heat is produced from the friction. Clouds hearing up in this manner are called protostars. 50% of the heat is retained by the protostar causing an increase in temperature. 50 % of the heat is radiated out of the protostar giving it an IR luminosity

Step 5 of star life

Over the next few million years gravity continues to pull mass inward, volume therefore decreases and density increases. As the density increases, the protostart gravity increases, pulling more mass towards the center, creating more friction and building up even more heat.

Step 6 of star life

When the temperature of the protostar builds up to 10,000,000 kelvin the gasses will be so compacted that the atomic nuclei will actually be pushed together (or fused) this fusion is a thermonuclear reaction that creates heavier elements and releases enormous amounts of light energy and heat. When fusion begins, gravity pulling inward and explosive pressure pushing outward will equilibrate, stoping all contraction. Once the first photons of light leave the protostar about one million years after fusion begins, it is officially a new star that has "wiinked on"

step 7 of star life

the fusion reaction in the core of a new star that converts hydrogen fuel into helium ash is 6 hydrogens -> 1helium + 2hydrogens + 6 high energy gamma ray light+ 2 v (neutrinos) This H-> He process continues for 90% of its lifetime

Step 8 of star life

The new star is age zero and will show up on an HR diagram on the main sequence. Its position on the main sequence may change slightly overtime but its original position is called its ZAMS position (Zero Age Main Sequence)

Lifetime Fuel Usage

99% of the star's mass is converted and mostly converted into heavier elements. 1% of the starts mass will be converted into light/heat energy by the nuclear fusion or fission reactions occuring in the core. Thus, 100% of the light and energy coming from a star is from only 1% of its mass. This conversion is possible through E=mc squared

Fusion continues until

The majority of the H has been converted into He ash

After core fusion stops:

The core contracts

Red Giants

While the core contracts because of no fusion, the surrounding envelope of remaining H gas is still fusing into He. These fusion reactions supply the envelope with its own outward pressure, allowing the envelope to swell to "giant" proportions. Because fusion is only going on in the envelope, less heat is being produced by the star and its temperature settles in the cooler red section of the HR diagram

Core contraction increases

Density and temperature

Core Test

Core test part A : Is the core moslty iron? if no=passed
Core test part B: Will the contracting core get hot enough to fuse heavier elements? Yes= passed

He used as fuel to fuse

C ash

Stellar Nucleosynthesis

Each time a star passes the core test, it will begin fusing new and heavier elements in the core of a hotter, more dense, and faster burning star than before

If core test is failed

Star death

Small and Medium stars

Up to 5 solar masses (95% of all stars)

Small stars will fail this part of the core test

part B

No nuclear reactions means

a decrease in outward pressure

Ejected envelope of a small and medium star is called

a planetary nebula

White hot core (40-60% of stars original mass) is called

a white dwarf

Typical white dwarf features:

2/3 mass of sun, 1/100 size of sum 100000000g/cm cubed density (1 car of mass-1 sugarcube of volume

giant stars

between 5 and 40 solar masses. they will fail paart A of the core test.

Ejected envelope of a giant star is called

a supernova

Typical Nuetron starts

3x mass of sun 20k in diameter, density is one sugarcube of volume= 200000000

Super giant stars

40 or more solar masses fail part A

Super giant stars will become

a singularity, and then a black hole

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