Why Do Some Star Maps Look So Similar To Each Other

One question we get here at TwinkleInTime is about why sometimes 2 different Star Maps might look very similar to each other.

We created an infographic to explain this and if you’re willing to explore the room you’re in a little bit, it might help with the explanation.

For this little exercise, you are Earth, the room is Outer Space, and everything that you see would be what is shown on your Star Map.

Stand up and look straight forward at the room you’re in. Now take a small step to the side. How much has your view changed? Probably not very much. This is why if you choose two locations that are close to each other, your star maps might look somewhat similar. 

Now take a bigger step.

Your view should have changed a bit more. Now walk to the other side of the room. Your view should have changed a lot more. Some things that you could see before are no longer visible and some things that you still can see might look a bit different as you look at it from a different angle. The closer the locations chosen on two Star Maps are to each other, the more overlap they will have.

The other thing that will affect the similarity of two Star Maps is the time of year.

As the Earth rotates around the sun, our view changes as well. Continuing our experiment, stay in place and rotate yourself slightly. The more you rotate, the more your view changes. Since a circle has 360° and it takes the Earth 365 days to travel around the sun, every night you will see about a 1° change in your view of the stars. That’s not very much, but if you do a quarter turn, that would represent about 3 months and your view should change a lot. If you do another quarter turn, you’ve completely turned around, which represents a change of half a year, and your view should have changed completely. Everything you saw before is still there; it’s just out of view.

To sum up, if you are looking at multiple Star Maps from Twinkle In Time, the closer they are, in physical location and time of year, the more similar they will be to each other.

The farther they are from each other, both physically and by date, the more different your Twinkle In Time Star Maps will be.