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Really. The study is looking at wide binaries, where stars are in very far orbits around each other, moving very slowly, but still gravitationally bound. For e
by Tuna-Fish 3y ago
Really. The study is looking at wide binaries, where stars are in very far orbits around each other, moving very slowly, but still gravitationally bound.
For example, the closest (non-sun) star to Earth, Proxima Centauri, orbits Alpha Centauri A and B with a semi-major axis of ~8700AU, or ~0.14 light years. It's orbital period is more than half a million years, it's orbital speed is ~500m/s, and the gravitational acceleration that keeps it in orbit is just 0.17nm/s².
That 0.17nm/s² is tiny, but it really adds up over half a million years.
- bjornsing 3y ago> That 0.17nm/s² is tiny, but it really adds up over half a million years. True. But we don’t have half a million years to make an observation. 0.17nm/s² over a year only adds up to a displacement of 85 km, and now we’re looking for a relatively small discrepancy in this expected movement? The radius of the sun is about 696000 km, for comparison.
- JPLeRouzic 3y agoI know nothing about physics, but just finding that an orbit isn't that if a body has an elliptic orbit means it is accelerating and decelerating constantly depending where it is in the orbit? I guess it's quite easy to measure periapsis and apoapsis even for stars or planets that have a nearly circular orbit.