B Are the stars of the constellations stationary?

[lighthouse1234]

Why is it that I can still use my 10 year old planisphere, if the stars are in motion?

 

[Baluncore]

Because the relative positions of the "fixed stars" change very slowly, so you do not notice it in your lifetime, unless you are an astronomer.

 

[lighthouse1234]

Someone wrote this to me: From that moving position these 'fixed stars' seem to be stationary,
hence are actually moving, even if they seemingly do not.

 

[Baluncore]

Is that a question?

From that moving position ...

From what moving position?

As the Earth orbits the Sun, the relative position of the nearest stars, move back and forth every 6 months, against the distant background. That is how we identify and measure the distance to nearby stars.

As the Sun moves through and with the galaxy, the relative positions of the fixed stars gradually move against the distant background.

 

[FactChecker]

Why is it that I can still use my 10 year old planisphere, if the stars are in motion?

The stars in constellations are so far away that they can be moving tremendously fast and we will not be able to notice it with the naked eye in our lifetime. The nearest star in Orion is Bellatrix, which is 250 light years away. A light year is 5.8 trillion miles. The farthest star in Orian is Alnilim, which is 1360 ly away. So the change in angle will be small unless/until they move very far sideways or up and down

 

[Vanadium 50]

Someone wrote this to me

There's a source!

 

[Vanadium 50]

The visible star with the largest proper motion is 61 Cygni. In 10 years, it moves about 2-1/2 arc-seconds. That's 0.15% of the apparent size of the moon.

 

[Drakkith]

Someone wrote this to me: From that moving position these 'fixed stars' seem to be stationary,
hence are actually moving, even if they seemingly do not.

If I stand far away from the train tracks near my house and watch a train go by, the train appears to move very slowly. If I hold my thumb up it takes about a second for the train to 'cross' behind it. But if I stand next to the tracks the train will cross behind my thumb in a small fraction of a second.

The same is true for stars. They may be moving very quickly relative to us, but they are so far away that they don't appear to be moving hardly at all.

 

[berkeman]

But if I stand next to the tracks the train will cross behind my thumb in a small fraction of a second.

"There's that guy again, trying to hitch a ride on our train..."