the.com/stellar orbits
stars don't sit still — they swing around their galaxy's dark, gravitational drain.
means the paths stars trace through a galaxy under the collective gravitational pull of everything else in it, not just one central mass.
from newton solved planetary orbits around a single sun, but galaxies are billions of suns pulling on each other at once — the math only got tractable in the 20th century once astronomers could measure rotation curves and realized the numbers demanded unseen mass.
sun's commuteabout 230 million years per lap
the giveawayorbit speeds revealed dark matter's existence
shapeoften elliptical, not neat circles
scalestars near galactic rim orbit too fast