I'm going to hope that this response does not throw the thread wildly off-topic, but I'm going to reply to what Rowan has just said.
"..how did ancient peoples know that Sirius was a binary star.."
They did not know that Sirius was a binary star as they didn't even know what a binary star was. We can only say that Sirius is a binary star because someone invented the term "binary star" and it happens to apply to Sirius. But no-one has ever been close enough to Sirius to verify this, and for all we know, when you get closer it could turn out to be something completely different entirely.
Even had they known what a binary star was, who are we to say that these ancient images depict Sirius as a binary star? This is merely the interpretation of recent experts who claim that it is Sirius depicted. Don't forget that the universe changes, and that the star (if that is what it is) may have since changed and is now different from the one they are supposed to have represented. You could argue that with a Barthesian critical bent, then once the artist has produced a piece, then it is out of his hands entirely and the true art is in each person's interpretation so if your expert claims that this is indeed Sirius depicted then that is as valid an argument as my saying that it looks more like a plate of scrambled egg. I doubt however, that you would allow this and so we return to the question that haunted pre-Barthes artistic criticism: "It seems like a satire on middle-class mores, but is that what the author intended?" Who are we to say whether the artist producing this "Sirius" image actually meant to depict Sirius?
Are your experts not exhibiting pride in attributing particular traits to ancient peoples they know very little about?