The Wobble of an Astrometric Binary
The motion of the Sirius system about its center of mass causes the proper
motion of the two stars across the celestial sphere to
wobble,
as illustrated in this
animation.
This can be used to detect the presence of an
unseen companion.
You may illustrate this by using the buttons in the
binary star orbit applet
to hide the orbits and to hide
one of the stars. The corresponding motion of the other star is what we
would see for Sirius A if it did not have proper motion on the
celestial sphere. This
motion,
coupled with the proper motion of the Sirius system,
gives the wobbling path noted above.
|