## Order of the Planets
> [!tip] **M**y **V**ery **E**asy **M**ethod **J**ust **S**peeds **U**p **N**aming **P**lanets**
0. Sun
1. Mercury
2. Venus
3. Earth
4. Mars
5. Juptier
6. Saturn
7. Uranus
8. Neptune
9. Pluto/TNP *(trans-Neptunian objects)*
## First Nine Chemical Elements
> [!tip] HHeLiBeBCNOF
> Pronounced 'heelie beb kenoff'.
1. Hydrogen
2. Helium
3. Lithium
4. Beryllium
5. Boron
6. Carbon
7. Nitrogen
8. Oxygen
9. Fluorine
## CNO Cycle
> [!tip] **CNO**... **NO**t **F**inished! **CNO** again!
![[CNOcycle.png]]
*(See [[_Stellar Nucleosynthesis#CNO Cycle]] for more details)*
## Spectral Classes
> [!tip] Oh Be A Fine Goat Kick Me
> For the Spectral Types: OBAFGKM.
>
> ![[OBAFGKM_goat.jpeg|align:center|300]]
^b814bb
## Stellar Populations
> [!tip] If you're young and rich, you're number 1!
> Young, metal-rich stars = Population I stars
## HR Diagram
> [!tip] Looks like a T-Rex
>
> ![[HR_1Mstages_TRex.png|align:center]]
^hr-diagram-lowM
> [!tip] Looks like an Emoji
>
> ![[HR_1Mstages_emoji.png|align:center]]
^hr-diagram-highM
## Inclination Angle
> [!tip] An inclination of zero makes a zero "$0
quot; in the sky.
> When $i=0$, the orbital plane and observing/sky plane are aligned. So, the orbit of the secondary body with make a "0" shape as it progressing about the primary body.
## Spectral Classification - Sun
> [!tip] The sun is a G2V star because its *GrooVy*.
## Stephan Boltzmann
> [!tip] Stephan-Boltzmann goes for a walk with you.
> $\sigma = 5.67 \times 10^{-8} \; {\rm W \, m^{-2} \, K^{4}}$
> 5 to 6 to 7 to 8
## Crab Nebula
> [!tip] CRABS COME IN THREES.
>
> $P = 30 \; \pu{ms} \hspace{2cm} \dot{P} = 10^{-13} \; \pu{s/s} \hspace{2cm} L_{\rm crab} = 75000 \; {\rm L_{\odot}} \simeq 3 \times 10^{31} \; \pu{W}$
>
> Observed in 1054. What comes after 5,4?? Its 3.
^crab
## Radiation Energy Transport
> [!tip] "Crack Platter" = $\kappa_{R} a c \quad \rho L T r$
>
> - Hot-headed people throw plates $\implies$ radiation energy transport.
> - $T$ = taller letter = higher power = 3
> - $r$ = shorter letter = lower power = 2
>
> $\frac{\mathrm{d} T}{\mathrm{d} r} = -\frac{3}{16 \pi} \cdot \frac{\kappa_{R}}{a c} \cdot \frac{\rho L}{T^{3} r^{2}} \hspace{1cm} \text{where} \hspace{1cm} a = \frac{4 \sigma}{c}$
^e7ef73
## Flux-Luminosity Relationship
> [!tip] Flux-Luminosity
> Different ways to remember it?
> - We all LAF (laugh) at the idea of trying to remember this equation. $\implies L = A \cdot F$
> - **F**lux **A**nd **L**uminosity = FAL $\implies F \cdot A = L$
## Cosmology Epoch Scaling-Dependence
> [!tip] 21 Savage comes before Numbers
> To remember the scaling relations for overdensities $\delta$ and scale factors $a$ with time $t$ in radiation and matter dominated epochs (of an [[Friedmann Equation|FLRW]] universe), for some reason I find it easy to remember the exponents this way (radiation happens first in the universe)
>
> - Rad-dom: $\delta \propto a^{2} \propto t^{1}$ (**21**, like the savage, or the drinking age in the US)
> - Matter-dom: $\delta \propto a^{1} \propto t^{2/3}$ (**123**, like the first 3 numbers)
>
> So, I guess just remember 21 and 123.
## Tully Fisher vs De Vaucouleurs
> [!tip] Fishing vs Haughty Old Guy
> [[Velocity dispersion#Tully-Fisher Relation]] is for spirals because whirlpools are in the ocean where fish live 🐟.
> [[Velocity Dispersion#Faber-Jackson Relation]] is for ellipticals because ellipticals are old and haughty (puffed up). And quarters were invented in the past so thats why its 4.
## Kepler's 3rd Law
> [!tip] Aw Good Morning 321
> To remember [[Kepler's Laws of Planetary Motion#Kepler's 3rd Law]] just remember "aw good morning 321"
> $a^{3} \omega^{2} = G M$
## Mass of SMBH
> [!tip] H(uh) $\beta$(ig boy)
>
> To measure the mass of a [[Black Hole#Supermassive Black Hole|SMBH]]: use the H$\beta$ lag to tell if it's a H(uh) $\beta$(ig boy)
## Virial Theorem
> [!tip] Its a TUTU
> Helps to not mess up the virial theorem signs: The virial theorem is a "TUTU" (from 2 and TU and the RHS is the top-down view of a tutu).
> $2T + U = 0$
>
> ![[tutu.png|align:center|300]]
## Spacetime Curvature
> [!tip] Open or Closed?
>
> To remember whether $\Omega_{k}$ positive or negative means an open or closed universe in the context of the [[Friedmann Equation|FLRW]] metric, just remember that a sphere is closed because I'm trapped inside it, and I have very **negative** feelings about this trapping (so $\Omega_{k} < 0$ is **closed**). We talk about $\Omega_{k}$ more than $k$, but just remember that they have a minus sign relative to one another so a negative $\Omega_{k}$ means a positive $k $ and vice versa.
>
> ![[trapped_man.jpg|align:center|300]]
## The Einasto Profile
> [!tip] Ei**mass**to
> The [[Galaxy Profiles#Einasto Profile]] is nice because it has a well-defined total mass. Ei**mass**to.
## Lyman Hydrogen Transitions
> [!tip] Long Lyman Lines
> The [[Spectral Features#Lyman Series|Lyman]] transitions are to the $n=1$ energy because on this plot they are the **L**ongest.
> Those LONG Lyman lines.
> ![[hydrogen_lines.png|align:center|300]]
## Binding Energy of Deuterium/Deuteron
> [!tip] DEUCEterium
> Deuterium has a binding energy of $2.22\,\pu{MeV}$ because deuceterium. two.
## Eddington Limit
> [!tip] "$L$oo$\kappa$, its a '34 GMc Eddington!"
>
> $L \cdot \kappa = 4 \pi G M c \hspace{1cm} \Leftrightarrow \hspace{1cm} L \approx 3 \times 10^{4} \; \left(\frac{M}{M_{\odot}}\right) \left(\frac{\kappa_{\odot}}{\kappa}\right) \; L_{\odot}$
> - Eddington sounds like a car model
> - GMC is a car company $\implies G M c$
> - '34 is the year of model $\implies 3 \times 10^{4}$
## Roman Telescope
> [!tip] The Roman Empire was BIG
> The [[Instruments#Roman|Nancy Grace Roman Telescope]] is an IR telescope with a very large FOV, like the Roman empire... it was also big.