A parsec is used for measuring large distances and equals about how many light-years?

A parsec is used for measuring large distances and equals about how many light-years?

• A. About 3.26 light-years
• B. About 1 light-year
• C. About 10 light-years
• D. About 0.3 light-years

Answer: (A)

A parsec is a distance unit defined by how far away a star must be for its annual parallax (based on Earth's orbit of 1 AU) to subtend an angle of 1 arcsecond. That geometry works out to about 206,265 astronomical units. When you convert that distance into light-years, you get roughly 3.26 light-years. So parsecs are a convenient way to express large cosmic distances, and one parsec is about 3.26 times the distance that light travels in a year. The other numbers are much smaller or larger than this scale, so they don’t match the defined size of a parsec. That’s why the best answer is about 3.26 light-years.

A parsec is a distance unit defined by how far away a star must be for its annual parallax (based on Earth's orbit of 1 AU) to subtend an angle of 1 arcsecond. That geometry works out to about 206,265 astronomical units. When you convert that distance into light-years, you get roughly 3.26 light-years. So parsecs are a convenient way to express large cosmic distances, and one parsec is about 3.26 times the distance that light travels in a year. The other numbers are much smaller or larger than this scale, so they don’t match the defined size of a parsec. That’s why the best answer is about 3.26 light-years.