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Question 18M.3.SL.TZ2.11

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Date May 2018 Marks available [Maximum mark: 13] Reference code 18M.3.SL.TZ2.11
Level SL Paper 3 Time zone TZ2
Command term Calculate, Determine, Discuss, Draw, Outline, Plot Question number 11 Adapted from N/A
11.
[Maximum mark: 13]
18M.3.SL.TZ2.11
(a)

Main sequence stars are in equilibrium under the action of forces. Outline how this equilibrium is achieved.

[2]

Markscheme

photon/fusion/radiation force/pressure balances gravitational force/pressure

gives both directions correctly (outwards radiation, inwards gravity)

 

OWTTE

[2 marks]

(b)

A main sequence star P, is 1.3 times the mass of the Sun. Calculate the luminosity of P relative to the Sun.

[1]

Markscheme

«L  ∝  M35 for main sequence»

luminosity of P = 2.5 «luminosity of the Sun»

[1 mark]

The following data apply to the star Gacrux.

Radius = 58.5 × 10 9  m Temperature = 3600  K Distance = 88  ly

(c.i)

The luminosity of the Sun L ⊙  is 3.85 × 1026 W. Determine the luminosity of Gacrux relative to the Sun.

[3]

Markscheme

LGacrux = 5.67 × 10–8 × 4π × (58.5 × 109)2 × 36004

LGacrux = 4.1 × 10–29 «W»

L G a c r u x L ⊙  «= 4.1 × 10 29 3.85 × 10 26 » = 1.1 × 103

[3 marks]

(c.ii)

The distance to Gacrux can be determined using stellar parallax. Outline why this method is not suitable for all stars.

[1]

Markscheme

if the star is too far then the parallax angle is too small to be measured

OR

stellar parallax is limited to closer stars

 

OWTTE

[1 mark]

A Hertzsprung–Russell (HR) diagram is shown.

On the HR diagram,

(d.i)

draw the main sequence.

[1]

Markscheme

line or area roughly inside shape shown – judge by eye

 

Accept straight line or straight area at roughly 45°

M18/4/PHYSI/SP3/ENG/TZ2/11.d.i/M

[1 mark]

(d.ii)

plot the position, using the letter P, of the main sequence star P you calculated in (b).

[1]

Markscheme

P between 1 L ⊙  and 10 1 L ⊙  on main sequence drawn

[1 mark]

(d.iii)

plot the position, using the letter G, of Gacrux.

[1]

Markscheme

at 10 3 L ⊙ , further to right than 5000 K and to the left of 2500 K (see shaded region)

 

M18/4/PHYSI/SP3/ENG/TZ2/11.d.iii/M

[1 mark]

(e)

Discuss, with reference to its change in mass, the evolution of star P from the main sequence until its final stable phase.

[3]

Markscheme

ALTERNATIVE 1

Main sequence to red giant

 

planetary nebula with mass reduction/loss

OR

planetary nebula with mention of remnant mass

 

white dwarf

 

ALTERNATIVE 2

Main sequence to red supergiant region

 

Supernova with mass reduction/loss

OR

Supernova with mention of remnant mass

 

neutron star

OR

Black hole

 

OWTTE for both alternatives

[3 marks]

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