Astronomy Question

Question

Use the link below to help answer the questions:

https://phet.colorado.edu/sims/html/gravity-and-orbits/latest/gravity-and-orbits_en.html

When you open the link, check the gravity force checkbox and set the star mass to our sun, then hit play.

1a) How many days does earth take to complete one revolution around the sun?

1b) Is the orbit more circular or elliptical?

Next, check the gravity force check box and set the star mass to 1.5, then hit play.

1c) How many days does earth take to complete one revolution around the star?

1d) What happens to the radial velocity of the planet when it is near to the star and when it is far from the star?

1e) Is the orbit more circular or elliptical?

Next, check the gravity force check box and set the star mass to 2, then hit play.

1f) How many days does earth take to complete one revolution around the star?

1g) What happens to the planet if it is revolving under the gravitational influence of such a huge star?

Thank you so much!

Answer 1

1a) Approximately 365 days (The easiest way to measure the number of days is to turn on the grid lines and the gravity force vector and pause the graphic when the vectors between the earth and the sun are parallel to the grid line that the planet started on originally)

1b) The orbit is very circular (turn on the path marker to see it)

1c) Approximately 191 days

1d) Radial velocity will increase when the planet is closer to the star, and decrease when it is farther away. (You can see this well if you turn on the velocity vectors)

1e) This orbit is more elliptical than the first orbit

1f) Approximately 138 days

1g) The planet will need to orbit very quickly because of the star's mass. In this case, as the star's mass increases, the orbit will also become increasingly elliptical as the average radius between the star and the planet becomes much smaller.