Answer to Question 1
First, stars are very far apart in relation to their sizes and their relative velocities, so they collide very infrequently. Only a tiny fraction of stars in our Galaxy have ever suffered a collision or close encounter with another star. Also, the gas pulled from the Sun and the star would be much too hot to condense to make planets, and it would have dispersed instead. Furthermore, even if planets did form from that gas, they would not have gone into stable orbits around the Sun.
Answer to Question 2
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The steps of the scientific method, also known as hypothesis testing
Roots of the keystone species hypothesis: does a higher proportion of predators in diverse communiti
Artist's conception of the birth of a star within a dense molecular cloud.
Star Map Eastern Horizon
Smooth Brittle Star.
Sea Star Body Plan