Question

True or false? A transiting exoplanet that blocks 0.01 percent of the parent star’s light has 1 10 of the star’s radius.

True or false? If 20 percent of stars have Earth-like planets in the habitable zone orbiting them, and there are about 1 trillion stars in our Local Group of galaxies (of which the Milky Way Galaxy is a member), then there are roughly 200 billion such planets in the Local Group of galaxies.

True or false? Exoplanets orbiting other stars should obey Kepler’s three laws of motion, more specifically Newton’s versions of them, but in each case, their host star replaces the Sun.

Answer 1

a) For the planet to block 0.01 % of the star's light, The ratio of area of the planets should be the same.

Since

So, the statement is true.

b) No of stars in our local group = 1 trillion = 10¹² stars.

Now, 20 % of them have planets.

So, no of planets = 10¹² *20/100 = 2*10¹¹ = 200 billion.

So, this statement is also true.

c) This statement is as well correct. The Kepler's laws follows the most fundamental laws of physics, like newton's laws of universal gravitation. These laws must not vary anywhere in the universe. So, for any planet-star system, these laws must hold. The mass and other parameters must be taken to be that of the star, and not our sun.