(a) This question considers exoplanets, the environments in which they are born, and their methods of detection.

(i) In Book 8 you were introduced to the discovery of the circumstellar disk around the star known as Beta Pictoris. With the knowledge that this object is 19.4 parsec away and using the fact that light travels at 3 x 108 m sâ?'1 calculate the approximate year that the light that was detected for the first time by astronomers on Earth originally left the system.

(ii) Figure 1 represents a plot of planet mass against radius of orbit. Both scales are logarithmic but their exact values are not important for this question (although note that both are assumed to increase in the normal directions, i.e. bottom to top on the vertical axis and left to right on the horizontal axis). The two curves plotted on the graph represent the limits of detection for two hypothetical space missions (Van and Mini); one of these is aimed at measuring planetary transits, the other is a telescope capable of studying microlensing events.

Figure 1 Plot showing detection limits of planet mass and orbit radius of exoplanets for two hypothetical space missions, Van and Mini.
Evaluate the prospects for detecting the three planets (P1, P2 and P3) using Van and Mini, and explain the principles that would be used for their detection by the two missions.