How far away, in kilometres, is Sirius from the sun?

Question

The distance from our sun to Sirius, the brightest star of the night sky, is 8.6 light years. A light year is the distance that light travels in one year (365 days).

How far away, in kilometres, is Sirius from the sun?

Answer 1

You asked this same question 2 days ago, and I presented the answer. My answer is the same as the one provided by @Gabriel L. How come you didn't accept my answer? Here is a copy of what I presented.

Speed of light = 3x10⁸ m/s

3x10⁸ m/s x 60 s / min x 60 min / hr x 24 hr / day = 2.59x10¹³ m / day

2.59x10¹³ m / day x 365 day / yr = 9.46x10¹⁵ m / year = 1 light year

9.46x10¹⁵ m / year / light year x 8.6 light years = 8.14x10¹⁶ m

8.14x10¹⁶ m x 1 km / 1000 m = 8.14x10¹³ km

(this is about 50,000,000,000 miles)

Answer 2

Hi Angelina! Let's answer this with a step-by-step approach:

What has the question given us? We have the distance from the sun to Sirius: 8.6 light years

And we can look up the speed of light: ~3 x 10⁸ m / second

So the question wants to know, how far is Sirius from the sun, if it takes light, moving at ~3 x 10⁸ m / second, 8.6 light years to reach it? The first thing we need to do is figure out how many meters light can move in 1 year:

3 x 10⁸ m / second x 60 s / min x 60 min / hr x 24 hr / day = 2.59 x 10¹³ m / day

2.59 x 10¹³ m / day x 365 day / year = 9.46 x 10¹⁵ m / year (and this is the distance, in meters, light is moving per year, in other words m / light-years.

Now the question is asking for distance in kilometers, and since we know that it takes 8.6 light-years, we can first multiply our value by 8.6, and then we simply have to convert our above number into km:

9.46 x 10¹⁵ m / light-years x 8.6 light-years = 8.14 x 10¹⁶ m

8.14 x 10¹⁶ m x 1 km / 1000 m = 8.14 x 10¹³ km