How do we know that stars are suns, and that they have planets?

Question

And how do we know their sizes and distances?

In: Physics

Answer 1

1) stars are sun’s because definition. Our Sun is a star. A big ball of hydrogen gas that’s undergoing fusion

2) when we observe a star that has a periodic dimming, that’s a sign there’s a planet that’s orbiting the star at the plane that intersects our line of sight with the star.

3) by observation and using math. The earth moves about our Sun and every 6 months, the position of the Earth is farthest away from its position 6 months ago. By measuring the difference in location in the view and knowing the distance of Earth orbit about the sun, you can calculate angle difference and the distance using trigonometry.