2020-05-01_Astronomy

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During his time spent on planetary
research, Slipher also managed to keep
investigating spectroscopic binary stars.
His work here led to a major break-
through, hailed by astronomers as a
milestone. He found that certain spectral
lines in the otherwise blurred spectra of
some stars were sharp and stationary,
and noted this phenomenon in a variety
of stars in Scorpius, Perseus, and Orion.
From this he concluded in 1909 that
interstellar gas must exist in widely

separated regions of space, producing

what he called “selective absorption of

light in space.” Some astronomers con-

gratulated Slipher for this conclusion, but

many others ignored the findings for a

long time. Observations in the 1920s

would finally prove Slipher correct.

Moreover, in December 1912, Slipher

used the spectrograph to discover the

presence of dust — or “pulverulent mat-

ter,” as he termed it — between the stars

of the famous Pleiades Cluster. Proving

that the dust near the star Merope in this

cluster was shining only by ref lected light

demonstrated the existence of stuff

between the stars; that stuff came to be

called the interstellar medium.

The breakthrough

The discovery of matter among the stars

of the Pleiades was a big one. This put

Slipher on the map, with a legitimate

claim to a major discovery in astrophys-

ics. He then turned toward solving the

biggest mystery of the age, the nature of

so-called spiral nebulae. These numer-

ous, faint, diffuse objects had remained

mysterious for a century and a half. The

German natural philosopher Immanuel

Kant had suggested they were separate,

large “island universes” of matter as early

as 1755. But the evidence of their nature

LEFT: The Slipher and Lampland families roll out

in the Lowell Stevens-Duryea car, with Verna

Lampland, Emma Slipher, and Marcia Slipher in the

back seat, and V.M. Slipher (driving), David Slipher,

and Carl Lampland in the front seat.

BELOW: V.M. Slipher made this image of a solar

eclipse expedition at Syracuse, Kansas, in 1918.

The discovery of matter among the stars of the Pleiades was a big one.

This put Slipher on the map, with a legitimate claim to a major discovery in astrophysics.