Download Apparent Brightness, Parallax and the Distance to Sirius

Apparent Brightness, Parallax and the Distance to Sirius Sirius has the largest apparent brightness of any star in the sky. Before people had discovered the phenomenon of parallax they had no idea how far away Sirius is. But suppose they had guessed that Sirius is just like our Sun. They would then have explored the consequences of assuming that the luminosity of Sirius equals that of our Sun. • The measured flux of light from Sirius is 1.2 X 10 – 4 ergs/ cm2 sec. From this, calculate how far away Sirius would be based on our assumption. Give your answer in cm, but then convert it to light years. • Predict what the parallax of Sirius would be in this case. • In fact the measured parallax of Sirius turns out to be 0.38 seconds of arc. What is the real distance to Sirius? Again, give it both in cm and light years. • What is the real luminosity of Sirius? Give your answer in ergs/sec. What is the ratio between the luminosity of Sirius and that of the Sun?