Suggest, using the graphs, why star X is most likely to be a main sequence star.

Show that the temperature of star X is approximately 10 000 K.

Write down the luminosity of star X (L_X) in terms of the luminosity of the Sun (L_s).

Determine the radius of star X (R_X) in terms of the radius of the Sun (R_s).

Estimate the mass of star X (M_X) in terms of the mass of the Sun (M_s).

Star X is likely to evolve into a stable white dwarf star.

Outline why the radius of a white dwarf star reaches a stable value.

the wavelengths of the dips correspond to the wavelength in the emission spectrum

the absorption lines in the spectrum of star X suggest it contains predominantly hydrogen

OR

main sequence stars are rich in hydrogen

[2 marks]

peak wavelength: 290 ± 10 «nm»

T = \(\frac{{2.9 \times {{10}^{-3}}}}{{290 \times {{10}^{ - 9}}}}\) = «10 000 ± 400 K»

Substitution in equation must be seen.

Allow ECF from MP1.

[2 marks][

35 ± 5L_s

[1 mark]

\(\frac{{{L_{\text{X}}}}}{{{L_{\text{s}}}}} = \frac{{R_{\text{X}}^2 \times {\text{T}}_{\text{X}}^4}}{{R_{\text{s}}^2 \times {\text{T}}_{\text{s}}^4}}\)

OR

\({R_{\text{X}}} = \sqrt {\frac{{{L_{\text{X}}}{\text{T}}_{\text{s}}^4}}{{{L_s}{\text{T}}_{\text{X}}^4}}}  \times {R_{\text{s}}}\)

\({R_{\text{X}}} = \sqrt {\frac{{35 \times {{6000}^4}}}{{10\,{{000}^4}}}}  \times {R_{\text{s}}}\) (mark for correct substitution)

R_X = 2.1R_s

Allow ECF from (b)(i).

Accept values in the range: 2.0 to 2.3R_s.

Allow TS in the range: 5500 K to 6500 K.

[3 marks]

M_X = \({(35)^{\frac{1}{{3.5}}}}\)M_s

M_X = 2.8M_s

Allow ECF from (b)(i).

Do not accept M_X = (35)\(^{\frac{1}{{3.5}}}\) for first marking point.

Accept values in the range: 2.6 to 2.9M_s.

[2 marks]

the star «core» collapses until the «inward and outward» forces / pressures are balanced

the outward force / pressure is due to electron degeneracy pressure «not radiation pressure»

[2 marks]