13.4 Hertzsprung - Russel Diagram and Star Life Cycle Flashcards
What is a hertzsprung - russel diagram?
A plot of stellar luminosity against surface temperature.
What is on the y-axis? What does it start at and finish ?
The luminosity (W), starts at 10^-4 and finishes at 10^6.
What is on the x-axis? What does it start at and finish?
The temperature on surface (K), starts at 40000 and finishes at 2500.
What scale is used on the y-axis?
logarithmic
What 4 stages of a star do we see on this diagram?
Main Sequence Star , Red Giant , Red Supergiant , White Dwarf
Where do we find White Dwarfs on the HR diagram?
Across about 20000K and 10^-4 , so along the bottom
What colours go from the left to right on the diagram?
blue,white,yellow,red
What does a long wavelength represent ?
Low temperature and therefore colour red.
What does a short wavelength represent?
High temperature and therefore colour blue.
Where are Red Giants on the HR diagram?
About 5000K and 10^2 , so to the right and middle ish
Where are Red SuperGiants on the HR diagram?
Top right, greatest luminosity,but to the right
Where are main sequence stars on the HR diagram?
Going from top left to bottom right, greatest variation.
What is the order of the life cycle of a star? State both possibilities.
Stellar Nebula
Protostar
Main Sequence Star
Red Giant Red Supergiant
White Dwarf Supernova
Black Hole or Neutron Star
Does the massive or smaller stars spend longer in the Main Sequnce stage?
Smaller stars spend longer on main sequence.
What is a stellar nebula ? - where does it come from?
Cloud of dust and gas, mostly comes from previous stars in supernova)
How does a stellar nebula turn into a protostar?
Clumps of the cloud contract slowly under gravity, until they collapse to form a protostar.
How does a protostar turn into a Main Sequence Star?
Protostars continue to contract under gravity and heat up to eventually (at a high temp) hydrogen nuclei fuse to form helium. This element creates enough pressure by energy release to cancel out gravitational collapse.
How does a MSS turn into the next stage and what is that stage?
When all hydrogen has been used up in fusion, cancelling gravity. The core contracts and gets denser. The outer layers exapnd and cool becoming a Red Giant or Red Supergiant. - as core contracts the greater temperature allows helium fusion and therefore layers to be ejected(well into this stage)
What determines whether a main sequence becomes a red giant or a red supergiant.
the mass of the star
If a MSS becomes a red giant what stage comes after? And how?
A planetary nebula, once layers have been ejected and drifted away, we are left with inonized gases and a dense core?
What follows a planetary nebula? How does it turn into this stage of the life cycle?
The white dwarf, under contraction due to gravity the core collapses upon itself until the electrons are able to exert pressure to balance this.
If a MSS becomes a red supergiant what stage of the life cycle comes after? And how?
A supernova, fusion keeps happening up to the creation of iron, at that stage the core cannot support it’s weight causing a collapse with all chemicals, gases and layers of the Red Supergiant. Collision with the core causes an explosion.
How does a supernova form a neutron star?
The core keeps contracting under gravity so that the electrons get squashed onto atomic nuclei, combining protons and electrons. This leaves a neutron star.
What causes a supernova?
The rebound of outer layers against a neutron star core.
How do we get a black hole?
After a supernova if neutrons cannot withstand gravity due to its great mass, the star collapses to form a black hole
What does it mean for luminosity if a star is more massive.
It would be greater.
In a HR diagram which stars are likely to change into giants first?
The ones in the top left of MSS then as temperature is decreasing othe stars will turn.
