[tacticalogic]

So where would the actual physical Sirius be, when its observed position is likewise on the horizon? That light left Sirius 8.6 years ago.

I'd think you'd need better measurements to determine that. If you're looking at an object that's exactly one light-day away, and stationary relative to the Earth, it's apparent position should be accurate, but the light you're using to locate the object actually left there at the same time yesterday.

[Ethan Clive Osgoode]

If you're looking at an object that's exactly one light-day away, and stationary relative to the Earth, it's apparent position should be accurate

And if the object is 1/2 light day away, where would it's real position be?

[gondramB]

>>So where would the actual physical Sirius be, when its observed position is likewise on the horizon? That light left Sirius 8.6 years ago.

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I’d think you’d need better measurements to determine that. If you’re looking at an object that’s exactly one light-day away, and stationary relative to the earth, it’s apparent position should be accurate, but the light you’re using to locate the object actually left there at the same time yesterday. <<

Sirius is receding from the sun about 150,000,000 miles per year so a first order answer would be about about 1.3 billion miles further away than it looks... plus or minus the 186 million miles that earths position from the sun varies.

Then you’d consider that Sirius only looks like a single star - its actually two stars orbiting each other...

At least that’s my guess... I have a physics degree but stayed the heck away from astronomy.