3 ms·

I have some questions on the "stellar parallax" illustration. If I remember correctly the speed of Sun around the milky way is much bigger than the speed of ea

by Rexxar 10y ago

I have some questions on the "stellar parallax" illustration. If I remember correctly the speed of Sun around the milky way is much bigger than the speed of earth around the Sun. So the position of the earth is completely different in June and December, because the sun has moved. So -> Do the parallax computation works only in one direction ? (perpendicularly to the sun trajectory ?) -> Does it works for nearest stars because they have roughly the same speed and direction than Sun ?

GFK_of_xmaspast 10y ago
> they have roughly the same speed and direction than Sun Are you sure about that? https://en.wikipedia.org/wiki/Barnard%27s_Star https://en.wikipedia.org/wiki/Barnard%27s_Star : "The proper motion of Barnard's Star corresponds to a relative lateral speed of 90 km/s. The 10.3 seconds of arc it travels annually amount to a quarter of a degree in a human lifetime, roughly half the angular diameter of the full Moon." https://en.wikipedia.org/wiki/Alpha_Centauri https://en.wikipedia.org/wiki/Alpha_Centauri "All components of Alpha Centauri display significant proper motions against the background sky, similar to the first-magnitude stars Sirius and Arcturus. Over the centuries, this causes the apparent stellar positions to slowly change. Such motions define the high-proper-motion stars"