DP Physics (last assessment 2024)

Question 17N.3.SL.TZ0.12c

Date	November 2017	Marks available	[Maximum mark: 2]	Reference code	17N.3.SL.TZ0.12c
Level	SL	Paper	3	Time zone	TZ0
Command term	Show	Question number	c	Adapted from	N/A

[Maximum mark: 2]

17N.3.SL.TZ0.12c

Sirius is a binary star. It is composed of two stars, Sirius A and Sirius B. Sirius A is a main sequence star.

(c)

The mass of Sirius B is about the same mass as the Sun. The luminosity of Sirius B is 2.5 % of the luminosity of the Sun. Show, with a calculation, that Sirius B is not a main sequence star.

[2]

Markscheme

use of the mass-luminosity relationship or ${\left( {\frac{{{M_{{\text{Sirius}}}}}}{{{M_{{\text{Sun}}}}}}} \right)^{3.5}}$ = 1

if Sirius B is on the main sequence then $\left( {\frac{{{L_{\,{\text{Sirius}}\,{\text{B}}}}}}{{L{\,_{{\text{Sun}}}}}}} \right)$ = 1 «which it is not»

Conclusion is given, justification must be stated

Allow reverse argument beginning with luminosity

Syllabus sections

Option D: Astrophysics

Option D: Astrophysics » Option D: Astrophysics (Core topics) » D.2 – Stellar characteristics and stellar evolution

Option D: Astrophysics » Option D: Astrophysics (Core topics)

Question 17N.3.SL.TZ0.12c

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