Cosmology: $\text{The}$ $\text{Expanding}$ $\text{Universe}$ 🚀
**$\text{Cosmology}$** is the study of the $\text{origin}$, $\text{evolution}$, and $\text{structure}$ of the $\text{Universe}$.
$\text{Hubble's}$ $\text{Law}$
The $\text{recessional}$ $\text{velocity}$ ($v$) of a $\text{galaxy}$ is $\text{proportional}$ to its $\text{distance}$ ($d$) from the $\text{observer}$.
$$\mathbf{v = H_0 d}$$$\text{Redshift}$
The $\text{stretching}$ of $\text{light}$ $\text{wavelengths}$ due to the $\text{expansion}$ of $\text{space}$. $\text{Strong}$ $\text{evidence}$ for the $\text{Big}$ $\text{Bang}$.
$\text{Dark}$ $\text{Matter}$ $\text{and}$ $\text{Energy}$
$\text{Dark}$ $\text{Matter}$ provides $\text{extra}$ $\text{gravity}$. $\text{Dark}$ $\text{Energy}$ drives the $\text{accelerated}$ $\text{expansion}$ of the $\text{Universe}$. Together, they make up $\approx$ $\mathbf{95}\%$ of $\text{total}$ $\text{energy}$ $\text{density}$.
Stellar $\text{Evolution}$: $\text{Life}$ $\text{and}$ $\text{Death}$ $\text{of}$ $\text{Stars}$ 🌟
$\text{Main}$ $\text{Sequence}$
Stars ($\text{like}$ $\text{our}$ $\text{Sun}$) $\text{fuse}$ $\text{Hydrogen}$ ($\text{H}$) into $\text{Helium}$ ($\text{He}$) in their $\text{core}$. This is $\text{most}$ of a $\text{star's}$ $\text{life}$.
$\text{High-Mass}$ $\text{Death}$
Core $\text{collapse}$ $\to$ $\text{Type}$ $\text{II}$ $\text{Supernova}$ $\to$ $\text{Neutron}$ $\text{Star}$ or $\text{Black}$ $\text{Hole}$ (if $\text{mass}$ $>$ $3$ $\text{Solar}$ $\text{Masses}$).
$\text{Low-Mass}$ $\text{Death}$
$\text{Red}$ $\text{Giant}$ $\to$ $\text{Planetary}$ $\text{Nebula}$ $\to$ $\mathbf{\text{White}}$ $\mathbf{\text{Dwarf}}$ (supported by $\text{electron}$ $\text{degeneracy}$ $\text{pressure}$).
Exoplanets $\text{and}$ $\text{Astrobiology}$ 🪐
**$\text{Exoplanets}$** are $\text{planets}$ $\text{orbiting}$ $\text{stars}$ $\text{other}$ $\text{than}$ $\text{our}$ $\text{Sun}$. Their $\text{detection}$ is $\text{central}$ to $\text{astrobiology}$.
$\text{Transit}$ $\text{Method}$
Detecting a $\text{dip}$ in $\text{star}$ $\text{brightness}$ as a $\text{planet}$ $\text{passes}$ in $\text{front}$ of it. $\text{Measures}$ $\text{planet}$ $\text{size}$.
$\text{Radial}$ $\text{Velocity}$ $\text{Method}$
Detecting a $\text{star's}$ $\text{wobble}$ ($\text{Doppler}$ $\text{Shift}$) due to the $\text{planet's}$ $\text{gravity}$. $\text{Measures}$ $\text{planet}$ $\text{mass}$.
$\text{Habitable}$ $\text{Zone}$ ($\text{HZ}$)
The $\text{region}$ around a $\text{star}$ where $\text{liquid}$ $\text{water}$ $\text{could}$ $\text{exist}$ on a $\text{planet's}$ $\text{surface}$.
Interactive: $\text{Hubble's}$ $\text{Law}$ $\text{Calculation}$ 🧮
Use $\text{Hubble's}$ $\text{Law}$ ($\mathbf{v = H_0 d}$) to $\text{estimate}$ the $\text{distance}$ to a $\text{galaxy}$.
$\text{Assume}$ $\text{Hubble}$ $\text{Constant}$ ($\mathbf{H_0}$) $= \mathbf{70} \text{ km/s/Mpc}$.
Problem:
A $\text{galaxy}$ is $\text{receding}$ ($\mathbf{v}$) at a $\text{speed}$ of $\mathbf{1400} \text{ km/s}$. $\text{What}$ is its $\text{distance}$ ($\mathbf{d}$) in $\text{Mpc}$?
$$\text{Equation}: d = \frac{v}{H_0} = \frac{1400 \text{ km/s}}{70 \text{ km/s/Mpc}} = ? \text{ Mpc}$$
⚡ $\text{Stellar}$ $\text{Evolution}$ $\text{Check}$!
Identify the $\text{force}$ or $\text{pressure}$ that $\text{supports}$ the $\text{star}$ at this $\text{stage}$.
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