Space Physics Flashcards
What type of star is our star classed as?
- Main sequence star
- dwarf star
What is the mass of out sun?
1 Solar Mass (2 x 10^30)
What is the typical mass of a star?
One greater than that of 1 Solar Mass (1M)
Where does fusion occur in the star?
the core only
What is the only type of fusion in a star?
Hydrogen to helium
What are located on the sun, in parts where it is cooler?
Sun spots
What are the layers of the sun (outer to innermost)?
Corona, chromosphere, photosphere with convection zone and core
What can be seen coming off the outside of the chromosphere?
Prominence
What is the temperature of the core of a main sequence star?
15 million Kelvin
What is the temperature of the photosphere of a main sequence star?
5,700 Kelvin
What is the visible part of a main sequence star?
Photosphere
What is found in the radiative zone?
Metal ions
What is found in the convection zone?
Atoms of helium and hydrogen
What is dust?
Any atoms or molecules that are not helium or hydrogen
Describe the formation of a main sequence star:
- Large mass of gas and dust begin to collapse gravitationally due to non-uniform density
- Transfer of g.p.e to k.e. results in an increase of temperature at the centre of the cloud
- When temperature is high enough, thermonuclear fusion initiates; hydrogen nuclei fuse together to form Helium nuclei
- After some time, an equilibrium is established between the continued gravitational collapse and the radiation pressure of photons emitted by the core
- A main sequence star is formed
Describe how a red giant is formed from a main sequence solar mass star:
- Hydrogen in core is exhausted
- Fusion ceases
- Radiation pressure is lost
- So equilibrium between gravitational collapse and radiation pressure is lost
- The core collapses
- G.P.E is converted into kinetic energy so temperature of the core increases
- Temperature is then sufficient for Helium fusion to initiate
- Increased temperature of core creates greater radiation pressure- star expands
- A red giant is formed
Describe the key features of a Red Giant:
- cooler surface than a main sequence star
- more luminous due to increased surface area
What is the composition of a white dwarf core?
Diamond
Describe how a red giant evolves further to a white dwarf:
- Helium in the core is exhausted
- Fusion ceases
- Radiation pressure is lost
- Equilibrium between gravitational collapse and radiation pressure is lost
- Core collapses
- G.P.E is converted into K.E. so the temperature of the core increases
- However, temperature is insufficient for carbon fusion to initiate
- Core continues to collapse until new equilibrium is established between gravitational collpase and electron pressure
- Outer layers of the star are ‘left behind’ to form a planetary nebula
- remaining mass is known as a white dwarf
Describe the key features of a white dwarf:
- denisty a million times greater than a main sequence star
- radius 100 times smaller than main sequence star (7000km)
- surface temperature around 100,000K compared to 1000K for main sequence star
- very low luminosity due to very small surface area
Describe the process at the end of the life of a star with a mass greater than 8 solar masses:
- After a long sequence of fusion events, the core of the star ends up as iron
- Iron fusion is endothermic
- The energy for iron fusion comes from the layers of the star outside the core
- All the star’s energy pours into the core in a fraction of a second
- A supernova explosion occurs
What could the result objects be of a supernova?
- Neutron Star
- Black Hole
What is the mass of a Neutron star supernova remnant?
1.5 solar masses
What is the mass of a black hole supernova remnant?
2.5 solar masses
What prevents further collapse in a neutron star?
The strong nuclear force