I spent some time over the weekend in the wilderness looking at the stars at night, thinking about how far away they must be as suns, yet barely visible to my eye.

The dimmest star visible to the human eye in good conditions is about +6 in magnitude. At that level, the number of photons reaching the eye is about 1,250 photons per second.

For perspective, the equivalent when looking at the sun (which you should never do) is 6 quadrillion (6.3 × 10¹⁵) photons per second. That’s nearly 13 orders of magnitude, or a million × a million × 10.

So yeah, those stars are indeed really far away.