English astronomer who made a determination of solar parallax,
using observations of the asteroid Eros. He also studied the speed of
rotation of the Earth, and the motions of the Sun, Moon, and planets.
Spencer Jones was born in London and studied at Cambridge. He worked
at the Royal Observatory, Greenwich, 1913-23; was His Majesty's Astronomer
on the Cape of Good Hope, South Africa, 1923-33; and ended his career
as the tenth Astronomer Royal 1933-55.
While at the Cape of Good Hope, Spencer Jones published a catalogue
containing the radial velocities of the southern stars, calculated the
orbits of a number of spectroscopic binary stars, and made a spectroscopic
determination of the constant of aberration. In 1925, he obtained and
described a long series of spectra of a nova which had appeared in the
constellation of Pictor.
Spencer Jones proved that fluctuations in the observed longitudes of
the Sun, Moon, and planets are due not to any peculiarities in their
motion, but to fluctuations in the angular velocity of rotation of the
Earth. He also investigated the Earth's magnetism and oblateness, and
he estimated the mass of the Moon.