13.4 Hertzsprung - Russel Diagram and Star Life Cycle Flashcards Preview

A-Level Physics EDEXCEL Year 2 > 13.4 Hertzsprung - Russel Diagram and Star Life Cycle > Flashcards

Flashcards in 13.4 Hertzsprung - Russel Diagram and Star Life Cycle Deck (27)
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1
Q

What is a hertzsprung - russel diagram?

A

A plot of stellar luminosity against surface temperature.

2
Q

What is on the y-axis? What does it start at and finish ?

A

The luminosity (W), starts at 10^-4 and finishes at 10^6.

3
Q

What is on the x-axis? What does it start at and finish?

A

The temperature on surface (K), starts at 40000 and finishes at 2500.

4
Q

What scale is used on the y-axis?

A

logarithmic

5
Q

What 4 stages of a star do we see on this diagram?

A

Main Sequence Star , Red Giant , Red Supergiant , White Dwarf

6
Q

Where do we find White Dwarfs on the HR diagram?

A

Across about 20000K and 10^-4 , so along the bottom

7
Q

What colours go from the left to right on the diagram?

A

blue,white,yellow,red

8
Q

What does a long wavelength represent ?

A

Low temperature and therefore colour red.

9
Q

What does a short wavelength represent?

A

High temperature and therefore colour blue.

10
Q

Where are Red Giants on the HR diagram?

A

About 5000K and 10^2 , so to the right and middle ish

11
Q

Where are Red SuperGiants on the HR diagram?

A

Top right, greatest luminosity,but to the right

12
Q

Where are main sequence stars on the HR diagram?

A

Going from top left to bottom right, greatest variation.

13
Q

What is the order of the life cycle of a star? State both possibilities.

A

Stellar Nebula
Protostar
Main Sequence Star
Red Giant Red Supergiant
White Dwarf Supernova
Black Hole or Neutron Star

14
Q

Does the massive or smaller stars spend longer in the Main Sequnce stage?

A

Smaller stars spend longer on main sequence.

15
Q

What is a stellar nebula ? - where does it come from?

A

Cloud of dust and gas, mostly comes from previous stars in supernova)

16
Q

How does a stellar nebula turn into a protostar?

A

Clumps of the cloud contract slowly under gravity, until they collapse to form a protostar.

17
Q

How does a protostar turn into a Main Sequence Star?

A

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.

18
Q

How does a MSS turn into the next stage and what is that stage?

A

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)

19
Q

What determines whether a main sequence becomes a red giant or a red supergiant.

A

the mass of the star

20
Q

If a MSS becomes a red giant what stage comes after? And how?

A

A planetary nebula, once layers have been ejected and drifted away, we are left with inonized gases and a dense core?

21
Q

What follows a planetary nebula? How does it turn into this stage of the life cycle?

A

The white dwarf, under contraction due to gravity the core collapses upon itself until the electrons are able to exert pressure to balance this.

22
Q

If a MSS becomes a red supergiant what stage of the life cycle comes after? And how?

A

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.

23
Q

How does a supernova form a neutron star?

A

The core keeps contracting under gravity so that the electrons get squashed onto atomic nuclei, combining protons and electrons. This leaves a neutron star.

24
Q

What causes a supernova?

A

The rebound of outer layers against a neutron star core.

25
Q

How do we get a black hole?

A

After a supernova if neutrons cannot withstand gravity due to its great mass, the star collapses to form a black hole

26
Q

What does it mean for luminosity if a star is more massive.

A

It would be greater.

27
Q

In a HR diagram which stars are likely to change into giants first?

A

The ones in the top left of MSS then as temperature is decreasing othe stars will turn.

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