Which unit is commonly used to describe distances to stars outside our solar system?

Which unit is commonly used to describe distances to stars outside our solar system?

• A. Kilometer
• B. Light-year
• C. Astronomical Unit
• D. Meter

Answer: (B)

Distances to stars are extremely large, so we use a unit tied to the speed of light. A light-year is the distance light travels in one year. Light moves about 300,000 kilometers each second, so in a year it covers roughly 9.46 trillion kilometers (about 5.88 trillion miles). This unit makes interstellar distances easier to grasp because it links distance to a universal constant—the speed of light—and to time. If you used kilometers or meters, the numbers would be so huge they’re hard to interpret. The astronomical unit is for measuring distances within our solar system, based on Earth’s distance from the Sun, and becomes impractical for stars. So the light-year is the standard unit for describing distances to stars outside our solar system.

Distances to stars are extremely large, so we use a unit tied to the speed of light. A light-year is the distance light travels in one year. Light moves about 300,000 kilometers each second, so in a year it covers roughly 9.46 trillion kilometers (about 5.88 trillion miles). This unit makes interstellar distances easier to grasp because it links distance to a universal constant—the speed of light—and to time. If you used kilometers or meters, the numbers would be so huge they’re hard to interpret. The astronomical unit is for measuring distances within our solar system, based on Earth’s distance from the Sun, and becomes impractical for stars. So the light-year is the standard unit for describing distances to stars outside our solar system.