Astrophysics Notes
ASTROPHYSICS
Galaxy = collection of large number of stars, mutually attracting each other through the gravitational force and staying together
No. Of stars varies between a few million and hundreds of billions. There are approximately 100bn galaxies in the universe
3 types of galaxies: 1. Spiral (Milky Way) 2. Elliptical (M49) 3. Irregular (Magellanic Clouds) – Anything that is not elliptical or spiral = irregular.
No specific structure, Large and small Magellanic clouds are the nearest to irregular galaxies.
Why is there a black hole?
Not enough evidence to support it but is widely believed to be true. – Cant see it but not a hole, gravitational force = so strong you cant see it, hence an absence of light = black hole (even though its technically not a hole).
Polaris = North Star
Constellations
Stars = Fusion reactors of gases. (Hydrogen + Helium) Them fusing = chain effect.
Interstellar dust coming together through mutual gravitational attraction
Nebulae = Dying star after its gone supernova./Cloud of gas and dust in space.
Nuclear Fusion = Very high temps are needed in order to begin the fusion process, 107K.
Star = Big ball of gas with fusion going on at the center held together by gravity
There are variations between stars, but by and large they’re really pretty simple.
Mass of star dictates its luminosity and temperature.
Gravity pulls outer layers in - Gas Pressure pushes them out
The more mass a star has = more central pressure
Luminosity of a star is the energy that it releases per second. Sun has a luminosity of 3.9×1026 J/s
The energy that arrives at the earth is only, a very small amount when compared to the total energy released by the sun.
Luminosity = Power
Distance travelled by the sun = d = 1.5 × 1011m
Average distance from earth to the sun = distance from earth to the sun.
Estimate how much energy falls on a surface of 1m2 in a year
3.9×1026W4πd2 = 1378.1W/m-2 =
Galaxy = collection of large number of stars, mutually attracting each other through the gravitational force and staying together
No. Of stars varies between a few million and hundreds of billions. There are approximately 100bn galaxies in the universe
3 types of galaxies: 1. Spiral (Milky Way) 2. Elliptical (M49) 3. Irregular (Magellanic Clouds) – Anything that is not elliptical or spiral = irregular.
No specific structure, Large and small Magellanic clouds are the nearest to irregular galaxies.
Why is there a black hole?
Not enough evidence to support it but is widely believed to be true. – Cant see it but not a hole, gravitational force = so strong you cant see it, hence an absence of light = black hole (even though its technically not a hole).
Polaris = North Star
Constellations
Stars = Fusion reactors of gases. (Hydrogen + Helium) Them fusing = chain effect.
Interstellar dust coming together through mutual gravitational attraction
Nebulae = Dying star after its gone supernova./Cloud of gas and dust in space.
Nuclear Fusion = Very high temps are needed in order to begin the fusion process, 107K.
Star = Big ball of gas with fusion going on at the center held together by gravity
There are variations between stars, but by and large they’re really pretty simple.
Mass of star dictates its luminosity and temperature.
Gravity pulls outer layers in - Gas Pressure pushes them out
The more mass a star has = more central pressure
Luminosity of a star is the energy that it releases per second. Sun has a luminosity of 3.9×1026 J/s
The energy that arrives at the earth is only, a very small amount when compared to the total energy released by the sun.
Luminosity = Power
Distance travelled by the sun = d = 1.5 × 1011m
Average distance from earth to the sun = distance from earth to the sun.
Estimate how much energy falls on a surface of 1m2 in a year
3.9×1026W4πd2 = 1378.1W/m-2 =