The study of the structure and evolution of the Cosmos from begining to end
Percentage of space the galaxies take up
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 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
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
Main unit of distance for cosmologists and astronomers. The distance that light can travel in a year.
Longer wavelenth, lower frequency, lower energy to shorter wavelength, higher frequency, higher energy:
Radio, Microwave, IR (infared), Visible, UV (Ultraviolet) Xray, Gamma
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
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"
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
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?
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
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 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
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
Small and Medium stars
Up to 5 solar masses (95% of all stars)
Small stars will fail this part of the core test
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
between 5 and 40 solar masses. they will fail paart A of the core test.
Ejected envelope of a giant star is called
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