Question 20N.3.SL.TZ0.17

$«\frac{L}{L_{\odot }}=\frac{M^{ 3.5}}{{M_{\odot }}^{3.5}}=5.{70}^{3.5}=» 442$ ✓

the luminosity of Eta (2630$L_{\odot }$) is very different «so it is not main sequence» ✓

Allow calculation of $L^{\frac{1}{3.5}}$ to give $M=\mathit{9}\mathit{.}\mathit{5}\mathit{ }{M}_{\odot }$ so not main sequence

OWTTE

$d«=\frac{1}{2.36\times {10}^{-3}}»=424 «\mathrm{pc}»$ ✓

Use of $d=\sqrt{\frac{L}{4\mathrm{\pi b}}}$ ✓

$=\sqrt{\frac{2630\times 3.83\times {10}^{26}}{4\mathrm{\pi }\times 7.20\times {10}^{-10}}}$ ✓

$«=\frac{1.055\times {10}^{19}}{3.26\times 9.46\times {10}^{15}}»=342«\mathrm{pc}»$ ✓

Award [3] marks for a bald correct answer between $\mathit{340}$ and $\mathit{344}\mathit{ }«\mathrm{pc}»$

parallax angle in milliarc seconds/very small/at the limits of measurement ✓

uncertainties/error in measuring $L$ οr $b$ or $\theta$ ✓

values same order of magnitude, so not significantly different ✓

Accept answers where MP1 and MP2 both refer to parallax angle

OWTTE

reference to change in size ✓
reference to change in temperature ✓
reference to periodicity of the process ✓
reference to transparency / opaqueness ✓