HQ3.4
\( 0 / 3 \) points (graded)
What is the distance between the centre of mass of the red star and the centre of mass of its companion? You may assume that the red star has a mass of \( 2 \times 10^{30} \mathrm{~kg} \), that its companion has the same mass, and that
\( G=6.67 \times 10^{-11} \mathrm{~N} \mathrm{~m}^{2} \mathrm{~kg}^{-2} \)
Enter the distance in metres:
HQ3. 2
1/1 point (graded)
How fast is the motion of the centre of mass of this system, along the line of sight to the Earth?
It is moving towards us at around \( 1000 \mathrm{~km} / \mathrm{s} \)
It is moving towards us at around \( 60 \mathrm{~km} / \mathrm{s} \)
It is neither moving towards nor away from us
It is moving away from us at around \( 50 \mathrm{~km} / \mathrm{s} \)
It is moving away from us at around \( 160 \mathrm{~km} / \mathrm{s} \)
It is moving away from us at around \( 1000 \mathrm{~km} / \mathrm{s} \)
