Observations with the Hubble Space Telescope revealed a planet about 16 AU from a star whose mass is the same as our Sun’s mass. How long does it take the planet to orbit the star?

Answer 1

Since the star's mass equals that of the sun, you can use the same form of Kepler's third law that applies to our solar system.

P^2 = a^3

In the above formula, P is the period in years and a is the distance from the star in a.u.

See http://spiff.rit.edu/classes/phys440/lectures/kepler3/kepler3.html
for more about the law

P^2 = (16)^3 = 4096
P = 64 years