Eli5: If we are moving trough the galaxy, how come we see the same stars in the sky every night?

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Our entire solarsystem is moving through space yet the same constellations cover our skies every night. Do these stars move with us or are they far away enough that they their movement isnt noticable to us and they look stagnant even though everything is moving?

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Anonymous 0 Comments

It’s all distance. The solar system is moving at about 140 miles per second in its orbit around the center of the galaxy. The stars near us are moving at similar speeds, but not exactly the same. So there is a lot of relative movement.

The closest star is 4.3 light years away. A light year is ~5,880,000,000,000 miles. The furthest stars you can see with the naked eye are about 4,000 light years distance (the galaxy is roughly 100,000 light years across). They have to move extremely large distances for that movement to be apparent. If a star was one light year away, to move 1 degree across the night sky it would have to travel ~103 billion miles relative to the solar system. At a 1,000 light years that changes to about 17.5 light years of travel needed (~107,200,000,000,000 miles). Even if the star was moving at 140 miles per second relative to us (which it wouldn’t, it would be much slower) it would take a star 1,000 light years away nearly 12,150 years to move just half a degree across the night sky. Half a degree is roughly the size of the moons diameter when you see it in the sky.

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