When I was in school (over 20 years ago in a backwoods town), I leaned all kinds of wrong things about science. I think this might be one of those things. Back then we were taught that—hypothetically—if the Sun were to instantly, inexplicably, be reduced to the size of a basketball (while maintaining its mass), all of the planets and everything else in the solar system would continue along their orbits as though nothing ever happened. Is this still considered accurate (if it ever was)? I currently suspect that other bodies in the solar system would either also reduce in size in proportion to the Sun's or be torn apart in the immediate aftermath of the Sun's change. So what would happen in the above hypothetical based on the current understanding? If the answer is the same as what I was taught way back when, is that theoretical, or has it been observed? Obviously stars don't just shrink for no reason, so when I ask if it's been observed what I'm asking is if a larger, lower mass body has been observed orbiting a smaller, denser one? Maybe around a neutron star? In a weightless environment, would a balloon orbit a baseball?