Question

) Canopus (alpha Carinae) is the second-brightest star in the night sky, its apparent magnitude is 0.7 m . Based on the parallax measurements of Hipparcos satellite, its parallax is approximately 0.01 arcseconds. (i) Find the distance to Canopus in parsecs and its absolute magnitude. [3 marks] (ii) Assuming that the absolute magnitude of the Sun is 4.8m show that the luminosity of Canopus in terms of the solar luminosity L⊙ is approximately 16000 L⊙. [2 marks] (iii) The emission spectrum of Canopus shows a peak at 0.4 m, while the solar spectrum has a peak at 0.50m, which corresponds to the effective temperature Tmax = 5800K at the Sun’s surface. Find the surface temperature of Canopus and its spectral class. [2 marks] (iv) Explain why the colour of Canopus is not blue; what colour is it? [2 marks]

Answer 1