Question

problem set #9 begin date: 11/7/2025 12:01:00 am due date: 11/13/2025 11:59:00 pm end date: 11/16/2025 11:59:00 pm
problem 3: (8% of assignment value)
a \galactic year\ as defined by astronomers is:
please select the best choice from the available options.
the time it takes the earth to go around the sun (starting with when its closest in its orbit to the center of the galaxy)
the time it took the milky way galaxy to develop spiral arms
the time it takes the sun to revolve once around the center of the milky way galaxy
the time it will take the sun to become a red giant and expand into the galaxy
the time it takes the outermost part of the solar system (the oort cloud) to rotate once relative to the galaxy)
submit hint feedback i give up!
4 submission(s) remaining
hints: 1% deduction per hint. hints remaining: 1 feedback: 1% deduction per feedback.

Explanation:

A galactic year is defined as the time it takes for the Sun to complete one orbit around the center of the Milky Way Galaxy. This is a standard astronomical definition. The other options are incorrect as they refer to different astronomical phenomena or incorrect orbital bodies (e.g., Earth - Sun orbit is a regular year, not a galactic year; development of spiral arms is a formation process, not a time - based orbital period; Sun becoming a red giant is a stellar evolution event, not an orbital period; Oort Cloud rotation relative to the Galaxy is not the defined galactic year).

Answer:

the time it takes the Sun to revolve once around the center of the Milky Way Galaxy