Question

A red supergiant star is ten times more massive than the sun. What would be the likely impact on the motion of Earth if the sun were replaced by this red supergiant?
A year on Earth would be shorter because Earth's orbital speed would increase.
A year on Earth would be shorter because Earth's orbital speed would decrease.
A day would be longer because the gravity experienced by Earth would be stronger.
A day would be longer because the gravity experienced by Earth would be weaker.

Answer 1

The answer is ‘A year on Earth would be shorter because Earth's orbital speed would increase.’ This is because the massive star has a larger gravitational pull on the earth than our sun. The revolution speed of a planet depends on the Sun's gravity and it's distance from the Sun. Additionally, the closer a planet is to the sun, the faster it revolves around it because of  it feels the sun’s gravity more than those planets farther from the star.