I guess this will be an easy one to break but I hope you catch my general idea. How far would you need to travel in space before you look at the sky and notice some constellations out of whack? (assume a well studied astronomer with a map in hand but no tools to measure anything)
What constellations would lose shape first? I presume this has to do with the distance to the stars that form it or maybe to the difference in distance to the different stars that form it.
How far before the whole sky looks just alien and strange with nothing you would recognize?
What constellations would hold their shape the longest?
I presume the answer to some of these questions would depend on whether you are travelling this way or that way. Right?
You can see it happen if you go watch Powers of Ten online. You have to be somewhere between 10 and 100 light-years away from the earth to see the constellations lose their familiar shape. Yes, closer stars seem to change position faster.
I don’t think direction of travel would make much apparent difference (except in determining which particular constellations you happened to be facing) until you got outside the galaxy, 10,000 light-years away or so. And when you’re all the way out in the boonies of intergalactic space, 100 million light-years away, it will just look like bright speckles everywhere you look.
Go watch the movie, it doesn’t take long and you’ll like it.
The first constellation to change noticeably would be whichever one now has the Sun in it. Even just within what’s usually thought of as the Solar System, you can already get to the point where the Sun just looks like a particularly bright star.
Beyond that obvious effect, you’ll get the best results with a constellation with one or more stars very close to us, moving in a direction perpendicular to a line from us to that star. Significant distortions would require travel of a distance some fraction of the distance to the star (precisely what fraction would depend on what distortion you’d consider “significant”, but a percent or two would probably do it). The closest naked-eye stars are Alpha Centauri, in Centaurus (4.3 ly), Sirius, in Canis Major (8.6 ly), and Procyon, in Canis Minor (11.4 ly), so those are the constellations it’d be easiest to distort.
Edit: Actually, you’d never notice any distortion in the shape of Canis Minor, since it doesn’t have any shape to begin with, being basically just two stars. You’d still notice with the centaur and big dog, though.
Edit again: I overlooked epsilon Eridani (10.8 ly) and epsilon Indi (11.2 ly).
IANAAstronomer, but I’d say it really all depends. In general though, I’m sure you’d have to be entirely beyond our solar system before anything becomes noticeably out of whack to your eye.
The most recognizable constellations being the Big Dipper, Orion, and Cassiopeia, I’m thinking a light year or two away from our sun, at least (but maybe more). THe problem is it’s so subjective, as it depends on just how familiar you are with its shape, and how long in your very gradual travel until you say, “Damn, that doesn’t really look like Orion anymore, the belt isn’t even lined up!”
I had watched that a million times (and loved it every time) and I don’t think I had ever paid much attention to that detail. Thanks for the pointer.
Wait, what? Which does?
That makes sense and is in line with my initial hunch.
Is there any constellation that would survive a trip outside the galaxy? It would have to be a constellation where all the “stars” are actually galaxies or similarly huge and bright objects, right? Is there such a thing?
I think it’s a tad confusing to talk about the “shape of a constellation” changing depending on whether it happens to be currently more or less lined up with the Sun.
Yes, if you back off of Earth far enough so that looking at the Sun doesn’t blot out everything else you see in the sky, you’ll see the Sun as a very very bright object against the background of some familiar constellation.
And then as you keep backing away, the first apparent change you’ll notice in the configuration of the stars is indeed that the Sun’s position with respect to that constellation will move. (That’s because the Sun is still much much closer to you than any other star, so its parallax or shift in relative position will be perceptible much sooner.)
However…I think it’s kind of “cheating” to count that phenomenon in with “constellations losing their shape”. The Sun isn’t really considered a part of any recognized constellation, and doesn’t play any part in forming their “shapes”.
(At least, not in our own solar system. For all I know, there may be a civilization orbiting some other star whose canonical sky map of constellations does include our Sun. “See that star there, Przckwiiirelo? That little faint one over on the right? That’s the Genital Wart in the constellation of the Great God Fuoozwkwi, and there’s a very interesting myth about how he got it.”)
And further away, on a world where our Sun is just a star catalog entry, some grandmother has just “bought” a new name for it, as a birthday gift for her grandson.
If you start with a triangle-shaped constellation (like, say, Triangulum), and stick another star in it, you’ve turned it into a quadrilateral. I’d certainly say that that counts as “changing shape”.
Oh, and others have mentioned Orion: While it is a familiar and fairly distinctive shape, the stars that make up that shape are all fairly distant, as visible stars go. It’d probably be the last constellation to lose its shape.
:dubious: By that reasoning, the zodiacal constellations are “changing shape” all the time, as the Sun and the various planets move in and out of them. I don’t think most observers would think of the “shapes” of constellations that way.
I think it makes much more sense to say that the “shape” of a constellation is a permanently (or nearly permanently) fixed configuration determined only by the (extra-solar-system) bodies that are traditionally identified with it.
The Sun or a planet or a comet or a nova or what-have-you may temporarily appear in a constellation, but it isn’t part of the constellation and doesn’t determine its “shape”.
Well, Centaurus and Leo would be the first affected, since they contain stars relatively close to Earth, but it depends what direction you’re going in.