Explain why a planet might not be in the habitable zone if its orbit is too close or too far away from its parent star.

The Kepler telescope monitors about $150,000$ stars and can detect the change in their light if a planet passes in front of the star. As of $2017$, about $3,500$ exoplanets had been confirmed orbiting $2,600$ stars.

Using the information above, calculate$:$

a$)$ the fraction of stars which have planets.

The Kepler telescope monitors about $150,000$ stars and can detect the change in their light if a planet passes in front of the star. As of $2017$, about $3,500$ exoplanets had been confirmed orbiting $2,600$ stars.

Using the information above, calculate$:$

b$)$ the average number of planets per star.

The Kepler telescope monitors about 150,000 stars and can detect the change in their light if a planet passes in front of the star. As of 20 l 7, about 3,500 exoplanets had been confirmed orbiting 2,600 stars.

From the above data, $\frac{13}{750}$ is the fraction of stars which have planets and the average number of stars per planet is $1.4$. Explain why, in reality, both these numbers are likely to be larger.