Mock Exam Review

Notes covering the topics on the mock exam review sheet are on the way!

Hertzsprung Russell Diagram

Pretty good HR Diagram I found online. Click on it to make it bigger.

Class Notes 3/25

Newton's Universe:

1. Infinite size
2. Infinite number of stars
3. Infinite age
4. Homogeneous distribution of stars

H-R Diagram:

• X-Axis: Temperature in K (Note: increases from right to left)
• Y-Axis: Luminosity in Watts
• Main Sequence: made up of dwarf stars (mostly red dwarfs)
• White Dwarfs: below the main sequence, near the lower left corner of the graph
• Cepheid Variables: near the center of the graph, slightly above the main sequence
  

Wolfram Alpha

This website is great for Physics:

www.wolframalpha.com

It seems like you can type in basically any physics concept or formula and it will tell you all about it and answer your math questions. It can do some pretty complicated stuff, and it will convert units if you want it to. I think this could be very helpful.

Class Notes 3/23

Olber's Paradox

1. Newtonian idea of the universe assumes infinite universe and infinite number of stars with homogeneous distribution
2. Number of stars of distance d is about d^2
3. L = b/(4πd^2)

Hubble

1. Discovered galaxies and the enormous number of them
2. The further away a galaxy was the more the Hydrogen spectrum was shifted toward the red.
3. v = H0(d) where H0 is called Hubble's constant
4. (∆λ) / (λref) = v/c
5. The universe is expanding leading to the Big Bang cosmology.
6. Ho = 2.2 x 10^4 m/sMly
7. From v = H0(d) and d = v(avg)T:
   T = d/v(avg) = 1/H0

Schwarzchild Radius:

R = (2GM) / (c^2)

More Astrophysics Notes

What determines the brightness of a star?

• b = L / (4πd²) [W/m²]

What determines the luminosity of a star?

• Assuming a blackbody radiator:

o L = σAT⁴

o σ = 5.67 x 10^-8 [W/m²K⁴]

What determines the surface temperature of a star?

• Wein's Law: T = (2.90 x 10^-3(K·m))/ (λ_max)

More massive stars are also more luminous.

Absolute magnitude (M) is the magnitude of a star when observed from 10 parsecs.

Relative magnitude (m) is the magnitude of a star when observed from the Earth (or nearby).

Stars radiate energy through hydrogen fusion.

F_g = GMm/d²

White dwarf- in equilibrium (not a black hole) due to "electron degeneracy"

1 parsec = 3.26 light-years

Astrophysics Notes

How is the Universe Organized?

· The force of gravity clusters matter at an astronomical scale.

· Clusters within the universe

o Solar Systems consist of: one or more stellar bodies, planets, moons, asteroids, comets, dwarf planets (e.g. Pluto, Eris), Kuiper-belt like debris

o Stellar clusters consist of solar systems

o Galaxies

o Galactic clusters consist of galaxies

· Stars and planets are different because stars emit light while planets reflect light.

· A light-year (ly) is the distance light travels in a year.

· 1 ly = (2.998 x 10⁸ m/s) (3.156 x 10⁷ s/yr) = 9.46 x 10¹⁵ m ≈ 10¹³ km

· Our galaxy is 100,000 ly wide, 2,000 ly tall

· Wein's Law for a blackbody radiator: λ_max = (2.90 x 10^-3) / T (kelvin)

· Gravity bends light

· Andromeda is 2 million ly away