Although we are familiar with the units mentioned above, there are situations where they are not as efficient. For example, to measure the distances between the stars, the kilometer is not very appropriate, as these distances are extremely large. Thus, another unit of measurement is used to make these measurements, called a light year .
The light year is a unit of distance used in astronomy.
A light year is the distance that light travels in a vacuum in one year.
To calculate how much the distance of 1 light-year is worth it is necessary to know the speed of light in vacuum, which is 299792.458 km/s, and consider that the time of a year, according to the Gregorian calendar, is 365, 2425 days. Now just convert the Gregorian calendar days into seconds and multiply by the speed of light in a vacuum. So we have the information that a light year is 9,460,536,068.016 km (9.46 trillion kilometers).
1 light year: 9,460,536,068.016 km
Below are the stars closest to Earth:
| stars | Distance from Earth |
| next Centauri | 4.24 light years |
| Alpha Centauri A | 4.35 light years |
| Alpha Centauri B | 4.35 light years |
| star of barnard | 5.98 light years |
| Wolf 359 | 7.78 light years |
For example, to say that a star is 10 light-years from Earth means to say that the light that that star emits travels 10 light-years (more than 9 trillion kilometers) to be seen by an observer on the Earth’s surface. .
