Which unit would you use to measure distance to a distant star?

Which unit would you use to measure distance to a distant star?

• A. Kilometers.
• B. Light-year.
• C. Astronomical unit.
• D. Light-second.

Answer: (B)

Distances to distant stars are best expressed in light-years because this unit ties distance to how far light travels in a specific time. A light-year is the distance light covers in one year, which makes interstellar distances easier to grasp—roughly 9.46 trillion kilometers. Using light-years keeps numbers meaningful and manageable when talking about stars hundreds or thousands of light-years away. Kilometers work for everyday distances but become impractically large numbers for stars. The astronomical unit measures the distance from Earth to the Sun, which is great for the solar system but far too small for other stars. A light-second is only about 300,000 kilometers—far too short for stellar scales. So the natural choice for measuring how far distant stars are is a light-year (with parsecs as another commonly used unit in astronomy).

Distances to distant stars are best expressed in light-years because this unit ties distance to how far light travels in a specific time. A light-year is the distance light covers in one year, which makes interstellar distances easier to grasp—roughly 9.46 trillion kilometers. Using light-years keeps numbers meaningful and manageable when talking about stars hundreds or thousands of light-years away.

Kilometers work for everyday distances but become impractically large numbers for stars. The astronomical unit measures the distance from Earth to the Sun, which is great for the solar system but far too small for other stars. A light-second is only about 300,000 kilometers—far too short for stellar scales. So the natural choice for measuring how far distant stars are is a light-year (with parsecs as another commonly used unit in astronomy).