Observing a Galaxy in a New Way: 100,000 Lightyears Across

[Cody Richeson]

I'm having a bit of trouble wording this particular question, but here goes. Let's say I'm observing a spiral galaxy which is 100,000 lightyears across. The furthermost stars are seen as they were 100,000 years ago (not counting the number of lightyears away from the galaxy I'm positioned). What if I were wearing a special visor that allowed me to see each star's current position? What would that look like? Would the galaxy no longer be spiral? Would all the stars be cramped together in some strange shape?

 

[phinds]

I'm having a bit of trouble wording this particular question, but here goes. Let's say I'm observing a spiral galaxy which is 100,000 lightyears across. The furthermost stars are seen as they were 100,000 years ago (not counting the number of lightyears away from the galaxy I'm positioned). What if I were wearing a special visor that allowed me to see each star's current position? What would that look like? Would the galaxy no longer be spiral? Would all the stars be cramped together in some strange shape?

Yes, you certainly are having trouble formulating the question.

You've neglected to say how far away it is and you have neglected to say whether you are seeing it from above (looks like a circle) or edge-on (looks like a bulbous rectangle).

If, for example, it is 10 billion light years away and you are seeing it from above then you are seeing it pretty much exactly as it was 10 billion years ago. If you are seeing it from right at the edge (physically impossible, for you right now, but let's just say) and edge-on, then the stars nearby are as they are and those on the other side are seen as they were 100,000 years ago.