---
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


# Hertzsprung-Russell diagram
- x-axis：Temperature
- y-axis：Luminosity
- 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 )