A nova is the sudden, brief brightening of a star (see Chapter 13). Suppose Earth astronomers see two novas occur simultaneously, one in the constellation Orion (The Hunter) and the other in the constellation Lyra (The Lyre). Both nova are the same distance from Earth, 2.5 x10³c·y, and are in exactly opposite directions from Earth. Observers on board an aircraft flying at 1000 km/h on a line from Orion toward Lyra see the same novas but note that they are not simultaneous. 

(a) For the observers on the aircraft, how much time separates the novas? 

(b) Which one occurs first? (Assume Earth is an inertial reference frame.)