Convergence Plots for Nearby Moving Groups

2014-01-05T18:19:30Z (GMT) by Adric Riedel
<p>Just as parallel lines meet at a point on the horizon, an assembly of stars moving in the same direction should produce paths across the sky that seem to meet at divergent and convergent points.</p> <p>These are convergence plots for a vast number of nearby stars suspected of being in various nearby young moving groups.  We have extended their proper motion vectors into great circles that encircle the sky, and found that all of their motions (to a lesser or greater extent) converge at points near the anti-solar point, which is the point on the sky that the Sun is moving from.  The Sun is actually passing through these clouds, and the slight difference between the anti-solar point and the group's convergent point is due to their own small motions perpendicular to the Sun's.</p> <p>Genuine members of moving groups should have great circles that pass very near those convergent points (although there is nothing preventing random field stars from sharing the motion of a moving group); objects that do not (found on many of these plots) are most likely not real members, at least of that particular group. </p> <p> </p> <p>By the same token, moving groups themselves that have no convergent point (such as Octans) are probably so scattered that they are not real kinematic entities.</p>