Proxima Centauri is the closest star to the Sun. How many kilometres separate us from it?
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Answer
About 40 trillion km
Its light takes a little over four years to reach us. Voyager 1, at its current speed, would need more than 70,000 years to cover the same distance.
How to estimate it
Start with the light-year. Light covers 300,000 km each second, and a year lasts about 30 million seconds, so one light-year is 300,000 × 30,000,000 = 9 trillion km. Proxima Centauri lies 4.2 light-years away, which gives 4.2 × 9 trillion, about 38 trillion km. The accepted distance is about 40 trillion km.
Source: NASA; ESO
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