32 ASTRONOMY • MAY 2020
Slipher’s astronomical studies went in
several simultaneous directions. Shortly
after his arrival in 1901, the observatory
received a state-of-the-art spectrograph
made for the 24-inch Clark refractor, the
institution’s main instrument. By 1902,
Slipher had worked out the bugs with this
tricky piece of equipment and made some
spectrograms of Mars, Jupiter, and Saturn
worthy of sharing with the astronomical
community. His own work focused on
radial velocities of stars and the discovery
of binary stars by measuring shifts in the
spectra of the visible component.
Slipher began to use this spectrograph
exhaustively. He studied planetary atmo-
spheres, such as that of Mars, and exam-
ined the rotation period of Venus. He
also studied the spectra of the giant outer
planets Uranus and Neptune. Attempting
to determine the rotation periods and
detection of various substances — such
as chlorophyll on Mars — took up much
of his research.
The Lowell staff poses
on the steps of the
24-inch Clark dome in
1905, with V.M. Slipher
in back, along with
Harry Hussey (back
left). In the middle are
John Duncan and
Wrexie Leonard. Out
front are Percival Lowell
and Carl Lampland.Revolutionary astronomer V.M. Slipher (third from
left) sits inside the 24-inch Clark refractor dome at
Lowell Observatory in 1905 with Harry Hussey,
Wrexie Leonard, Percival Lowell, Carl Lampland, and
John Duncan.