Stellar PhysicsM

# Stellar PhysicsM - 1(a(i spectral class 1 Accept colour...

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Unformatted text preview: 1. (a) (i) spectral class; 1 Accept colour sequence. (ii) absolute magnitude; 1 (b) 4 Star Type of star A Main sequence; B Super Red Giant; C White Dwarf; D Main sequence; Award [1] for each correct name. (c) B more luminous than A; and has lower temperature than A; so from the Stefan-Boltzmann law; B has greater area (radius); 3 max (d) use of L = 4π bd 2 ; from the H-R diagram L B = 10 6 L Sun ; therefore sun B L L = 10 6 = 3 2 B 8 10 1.4 10 . 7 × × ×- d ; to give d B = 1.4 × 10 8 AU ( ≈ 700 pc); 4 No mark is awarded for the conversion from AU to pc. (e) at this distance the parallax angle is too small to be measured accurately; OWTTE ; 1 max Do not accept “it’s too far away” [14] 2. (a) mass; 1 (b) Chandrasekhar limit defines the maximum mass that a white dwarf can have; at a mass equal to the limit the core of the star is prevented from contracting further by electrons; above this mass the electrons cannot support the core and it further contracts causing the electrons to combine with protons to form neutrons; 1 OWTTE ; 3 max (c) pulsar; 1 [5] 3. (a) Earth → Mars → Jupiter → Pluto; 2 max All correct [2] , two in the wrong place [1] . (b) Pluto → Mars → Earth → Jupiter; 2 max All correct [2] , two in the wrong place [1] . [4] 4. (a) p Earth January Earth July Sun Mark the definition of p and description of its measurement along with the diagram. Essentially diagram should : show p ; position of Sun; position of Earth; then definition of p = Sun) from star of distance ( Sun) from Earth of distance ( ; diagram should show Earth positions separated by about six months; then description should mention that angle of sight is measured at these two positions such that the difference between these two angles is equal to 2 p ; 6 max Award [6 max] for a clear description and diagram, [3] for an average and [1] for some rudimentary idea. Mark diagram and description together. 2 (b) d = 549 . 1 1 = p = 1.82 pc; = 1.82 × 3.26 = 5.94 ly; 2 max (c) (i) the radiant power from a star; that is incident per m 2 of the Earth’s surface; Alternatively, define from b = 2 π 4 d L but terms must be defined to obtain the mark. definition of L ; definition of d ; 2 max (ii) L = 4π d 2 b ; therefore, S S B B S B b d b d L L 2 2 = ; d S = 1AU, d B = 3.8 × 10 5 AU; therefore, S B L L = (3.8) 2 × 10 10 × 2.6 × 10 –14 = 3.8 × 10 –3 ; 4 max Allow any answer between (3.0 and 4.0) × 10 –3 . (d) (i) temperature too low for it to be a white dwarf; 1 max (ii) luminosity too low for it to be a red giant; 1 max [16] 5. (a) fusion; of hydrogen to form helium; 2 max Responses must have all three aspects correct eg “nuclear fusion” would receive [0] , “hydrogen forms helium”, would receive [1] ....
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Stellar PhysicsM - 1(a(i spectral class 1 Accept colour...

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