My curious kids asked me this on the way to school and I honestly can’t answer it. Tried googling it but I keep getting the unit of measure as an answer rather than the method.
In: Planetary Science
For nearby stars a method called Parallax is used.
If you held an object close to your face and observe it with only your left or right eye (the other one being closed) you’d notice that there’s a difference in the background behind the object. Basically measuring how far apart your eyes are and taking the angle from your eye to the object in front of you enables you to measure the distance to said object.
For more distant stars (>400ly) a range of methods are used that measure the brightness of the star. This is pretty self explanatory, objects with an intrinsic brightness will appear dimmer the farther they are.
For very distant stars it is by measuring something called redshift. If you take an slinky, imagine the it magically glows blue. The more you stretch it, the redder it becomes. Now imagine light travelling to us from distant objects. That light is stretched to the red part of the visible light spectrum because the universe is expanding and distant objects are moving away from us.
I imagine this one would be difficult to explain to the kids, I don’t really know how to explain this phenomenon in a more digestable way lol.
Hope that’s helpful
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