---
# System prepended metadata

title: Stars
tags: [' Science and Life', ' 通識', NTNU, ' Introduction to Astronomy']

---

---
title: Stars
tags: NTNU, 通識, Science and Life, Introduction to Astronomy
---
# Star Life - Stellar Evolution
- Red Giant Star
    - Losing gas form
        - Planetary Nebula
        - Supernova
- After lose gas ( from less mass to massive mass )
    - White Dwarf ( Sun will be )
    - Neutron Star
        - ( Pulsar ) a kind of Neutron Star
    - Black Hole

![](https://i.imgur.com/VB249Tj.png)

# Hertzsprung-Russell diagram
- x-axis：Temperature
- y-axis：Luminosity
![](https://i.imgur.com/aaZiola.png)
- Main sequence
    - nuclear fusion of hydrogen into helium

# Schwarzschild radius
- calculate
    $r$~sch~ = $\dfrac{2GM}{c^2}$
- the SUN is 3KM
- So $r$~sch~ =$\dfrac{3M}{M~sun~}$

# Exoplanet
- Explain
    - It is a planet outside the Solar System and orbit with stellar
- How to find
    - Direct imaging
        - possible but not very useful
    - Transit Detection
        - useful
    - Color method
        - use Doppler effect of the Sun 
- Habitable Zone
    - liquid water exist or not ( roughly )
        - Kepler-186f ( Similar to the Earth )
