26 ASTRONOMY • APRIL 2021
Both namesake women were
towering figures in their respec-
tive fields of study. Vera C. Rubin
produced compelling evidence of
dark matter, ushering in what
The New York Times called a
“Copernican-scale change” in
cosmology. Nancy Grace Roman’s
research led to fundamental
insights about our galaxy’s struc-
ture. As NASA’s first chief of
astronomy, Roman also became
known as the “mother” of the
Hubble Space Telescope and was
a prime driver behind numerous
other space observatories.
Like Rubin and Roman’s biog-
raphies, both observatories are
packed with superlatives. TheRubin Observatory, expected to
rev up atop a mountain in Chile
late next year and achieve full
operation in late 2023, features
the world’s first 3.2-billion-pixel
digital camera. Its 8.4-meter
Simonyi Survey Telescope’s
design is so unique that it gar-
nered $40 million in private
funding, principally from
Microsoft gurus Charles Simonyi
and Bill Gates, long before federal
funding kicked in for the rest of
the project.
The Roman Space Telescope,
for its part, packs the same bril-
liant sub-arcsecond resolution as
Hubble, but covers a field of view
100 times greater and can switch
targets much more quickly. Its
focus on near-infrared wave-
lengths allows it to penetrate dust
and gas beyond Hubble’s vision.
Following Earth from afar while
sharing its orbit around the Sun,
Roman will be up to 1,000 times
more efficient than Hubble as a
survey telescope.
The massive amount of data
produced by both observatories
will require specialized algo-
rithms and, for Rubin, dedicated
processing centers to handle the
deluge of new information. If all
goes as planned, the two observa-
tories will play key roles inadvancing the field of astronomy
— contributions fitting of their
namesakes, who did the same in
their lifetimes.Shedding light
on dark matter
Dark matter was first postulated
in 1933 by Swiss astronomer
Fritz Zwicky when he found that
the galaxies of the Coma Cluster
were moving too fast for the group
to stick together based on the visi-
ble content of its galaxies. His idea
was controversial: Without what
he called dunkle Materie, or dark
matter, only a change in the laws
of physics could explain how our
universe holds itself together.
Four decades later, Rubin came
to the topic while seeking safe
harbor from the controversy and
“competitive atmosphere,” as she
called it, of her previous work on
the distributions and motions of
galaxies. She and instrumentalist
Kent Ford — who developed the
specialized spectrograph central
to her research — published semi-
nal papers on the rotation curves
of spiral galaxies. Rubin found
that stars orbiting at the outskirts
of galaxies were moving inexpli-
cably fast. In other words, the gal-
axies’ rotation curves were f lat.
Physics dictates that the far-
ther from a concentration of mass
something orbits, the weaker the
gravitational force it experiences
and the slower it moves. Based on
the amount of visible matter in
the outskirts of these galaxies,
which dropped off with distance,
the stars should be orbiting more
slowly. But as Rubin looked to a
galaxy’s fringes, she found that
stars kept up their speed, as if
under the inf luence of the gravi-
tational pull of some unseen
matter.
Rubin’s measurements were
compelling evidence that some
invisible material — Zwicky’s
dunkle Materie — resided within
and around galaxies. Dark matter
and the equally mysterious dark
energy — the presumed explana-
tion for the universe’s acceleratingTOP: A triumphant
team poses with the
8.4-meter Simonyi
Survey Telescope’s
primary and tertiary
mirror blank in 2008.
The mirror was cast
at the University of
Arizona’s Steward
Observatory Mirror
Laboratory in
Tucson, Arizona.
HOWARD LESTER/LSST
CORPORATION
ABOVE: Engineers
test the setup of the
Rubin Observatory’s
3,200-megapixel
camera in a clean
room at the summit.
ANDY FREEBERG/SLAC NATIONAL
ACCELERATOR LABORATORY