First,I’ve just come across this processed photo which showed what the Andromeda galaxy looked like if it was really bright
Andromeda if it were brighter - see also Phil Plait’s article about it: Yes, That Picture of the Moon and the Andromeda Galaxy Is About Right.
It may look far too large but you only see the central part of the galaxy by eye or with binoculars.
So, how could it get that bright? I think you need to answer that first.
If it is by having many more stars - well the Andromeda galaxy’s apparent magnitude is 3.4. Suppose it was made so bright it is as bright as a full Moon, so -12.6 then that’s 16 magnitudes difference in brightness. Five magnitude steps correspond to a factor of 100 in brightness, so - suppose it is only magnitude -11.6 just to make the calculations easier, then it’s 10,000 times brighter. So there are 10,000 times as many stars.
Well that would be true of our galaxy too, so at present the chance of a star getting as close as Neptune in a one million year period is 1 in 2.8 million. But if there were 10,000 as many stars, then it would be a chance of 1 in 280, so over the age of our solar system, we’d have many stars pass closer than Neptune. So our solar system wouldn’t be as stable.
The total integrated brightness of night sky is −6.50. make it 15 magnitudes brighter and that’s -21.5, about as bright as the Sun as seen from Saturn, and far brighter than the Moon. We wouldn’t have night; it would be quite bright all night and you’d see colour easily during the night time. The Moon wouldn’t make any noticeable difference to the brightness of the sky, even at full Moon.
So, anyway those are a few consequences but I’m sure there’d be many more.
If instead the stars are all somehow brighter, but same number, change in laws of physics, then we would need to be living on a planet more distant from the Sun because it would then be far too bright.
It’s fun to think about but it would all depend on how exactly the galaxies were brighter.
Another idea is just that our eyes are much more sensitive, in which case there’d be no consequences except that we’d all have superb night vision. I don’t see any reason why we couldn’t all have eyes able to see galaxies at night more easily. To start with, eyes like owls, adapted to see at night, larger eyes, more sensitive pigments in the retina etc. And then protection in daytime, just much smaller pupils to not let too much light in in daytime.
I just used Wikipedia as my source for those figures and didn’t bother to check them up yet, they are usually reasonably reliable about this sort of thing, so regard this as preliminary for now, I need to come back and check their sources for the figures:
About the Author
