Can someone briefly explain to me how they measure both distance (length or width) and temprature in space? For example, you'll see a picture of a nubula and astronomers will say it is something like 40 light years from one end to the other. But how can they measure that accurately from something that is clearly so far away?
Similarly they'll name a star that is 100x larger than our sun with "X" amount of mass, and "X" degrees temperature. Again, how can they measure that kind of stuff?
I understand the doppler affect and how they can judge directional movement either towards or away from us by shifts in light waves, but what if something is moving perpendicular to our line of vision?
I also kind of comprehend how they use light defraction to determine chemical composition of distant objects, but is this how they are determining temperature and mass?