13.4 Hertzsprung - Russel Diagram and Star Life Cycle

Question 1

What is a hertzsprung - russel diagram?

Answer 1

A plot of stellar luminosity against surface temperature.

Question 2

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

Answer 2

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

Question 3

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

Answer 3

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

Question 4

What scale is used on the y-axis?

Answer 4

logarithmic

Question 5

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

Answer 5

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

Question 6

Where do we find White Dwarfs on the HR diagram?

Answer 6

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

Question 7

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

Answer 7

blue,white,yellow,red

Question 8

What does a long wavelength represent ?

Answer 8

Low temperature and therefore colour red.

Question 9

What does a short wavelength represent?

Answer 9

High temperature and therefore colour blue.

Question 10

Where are Red Giants on the HR diagram?

Answer 10

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

Question 11

Where are Red SuperGiants on the HR diagram?

Answer 11

Top right, greatest luminosity,but to the right

Question 12

Where are main sequence stars on the HR diagram?

Answer 12

Going from top left to bottom right, greatest variation.

Question 13

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

Answer 13

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

Question 14

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

Answer 14

Smaller stars spend longer on main sequence.

Question 15

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

Answer 15

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

Question 16

How does a stellar nebula turn into a protostar?

Answer 16

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

Question 17

How does a protostar turn into a Main Sequence Star?

Answer 17

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.

Question 18

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

Answer 18

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)

Question 19

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

Answer 19

the mass of the star

Question 20

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

Answer 20

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

Question 21

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

Answer 21

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

Question 22

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

Answer 22

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.

Question 23

How does a supernova form a neutron star?

Answer 23

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

Question 24

What causes a supernova?

Answer 24

The rebound of outer layers against a neutron star core.

Question 25

How do we get a black hole?

Answer 25

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

Question 26

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

Answer 26

It would be greater.

Question 27

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

Answer 27

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