# A planet orbiting a star

There is a problem:
"The distance of Barnard’s star is 1.83 pc and mass 0.135 M. It has been suggested that it oscillates with an amplitude of 0.026" in 25 year periods. Assuming this oscillation is caused by a planet, find the mass and radius of the orbit of this planet."
My question is what is 0.026"? Is it the angular size of 2*a of the star's orbit?

Astronuc
Staff Emeritus
There is a problem:
"The distance of Barnard’s star is 1.83 pc and mass 0.135 M. It has been suggested that it oscillates with an amplitude of 0.026" in 25 year periods. Assuming this oscillation is caused by a planet, find the mass and radius of the orbit of this planet."
My question is what is 0.026"? Is it the angular size of 2*a of the star's orbit?
I imagine that the 0.026'' is 0.026 arcseconds as measured by the observer on earth. One has a distance to the star of 1.83 pc.

There are some symbols that appear as boxes.

I don't know what it means that "the star oscillates with an amplitude of 0.026 arcsec"?
Does it mean that the angular size of its elliptical orbit (2a) around center of mass is 0.026? or whatelse?

Astronuc
Staff Emeritus