They point the new glass at Sirius because it is bright and will show the faults in a lens. Alvan Graham Clark sees a faint point beside it. Not a ghost of the optics. A star. Bessel had already said Sirius wobbled as if something massive were there. The companion had been a number. Now it is a speck.

The lens was not built to hunt companions. It was built to be judged. The sky used the test.

Sirius B is a white dwarf, about as massive as the Sun, as small as the Earth. Clark had a faint star and a famous primary. The density, the electron degeneracy, the limit Chandrasekhar will name, are later offices.