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JOSEPH-LOUIS LAGRANGE
1736–1813
French–Italian mathematician and
astronomer Joseph-Louis Lagrange
studied celestial mechanics and
the effects of gravity. He explored
mathematically the ways in which
the gravitational pulls within a
system of three bodies, such as the
sun, Earth, and the moon, combine
with one another. His work led to the
discovery of positions with stable
orbits for a small body orbiting two
larger ones, now called Lagrange
points. Space telescopes are often
placed near Lagrange points for their
orbits around Earth and the sun.
See also: Gravitational theory
66–73 ■ Studying distant stars
304–05
JEAN BAPTISTE JOSEPH
DELAMBRE
1736–1813
A leading figure in scientific circles
during the French Revolution, in
1792 Delambre was tasked with
measuring the length of the arc of the
meridian from Dunkirk to Barcelona.
This was to refine the new metric
system, which defined the meter as
1/10,000,000 of the distance from
the North Pole to the equator. He
completed the task in 1798. From
1804, Delambre served as the
director of the prestigious Paris
Observatory. His astronomical
work included the production
of accurate tables showing the
positions of Jupiter’s moons. In
1809, he estimated that light from
the sun takes 8 minutes 12 seconds
to reach Earth (the figure is now
measured at 8 minutes 20 seconds).
See also: Gravitational
disturbances 92–93
BENJAMIN APTHORP GOULD
1824–1896A child prodigy, American Benjamin
Apthorp Gould graduated early from
Harvard University before moving
to Germany to study under the
renowned mathematician Friedrich
Gauss in 1845. In Europe, he earneda
Ph.D. in astronomy—the first
American to receive a doctorate in
the subject. He returned to the US in
1849 determined to raise the profile
of American astronomy. To this
end, he founded The Astronomical
Journal to publish research from the
United States; the journal continues
to this day. Between 1868 and 1885,
Gould worked in Argentina, where
he founded the National Observatory
in Córdoba. He also helped to
set up the Argentine National
Weather Service. Gould produced
a comprehensive catalog of
the bright stars visible from the
southern hemisphere, which
he published in 1879 as the
Uranometria Argentina.RICHARD CARRINGTON
1826–1875British amateur astronomer
Richard Carrington carried out
careful observations of the sun
over the course of many years.
In 1859, he was the first person to
observe a solar flare—a magnetic
explosion on the surface of the
sun that causes a surge of visible
light. The flare was followed by
disruption to worldwide telegraph
systems, and Carrington suggested
that such solar activity might have
an electrical effect on Earth.
In 1863, through his records of
the movements of sunspots, he
demonstrated that differentparts of the sun were rotating
at different speeds.
See also: Galileo’s telescope
56–63 ■ The surface of the sun 103ISAAC ROBERTS
1829–1904In the 1880s, British amateur
astronomer Isaac Roberts made
important advances in the field
of astrophotography, enabling
photographs of the night sky to
reveal structures invisible to the
naked eye for the first time. Roberts
developed an instrument that
allowed very long exposure times,
and thus the collection of more light.
He kept the telescope pointing at
exactly the same point in the sky by
adjusting it to compensate for the
rotation of Earth. Roberts’ most
famous image is an 1888 photograph
of the Andromeda nebula, now
known to be a galaxy, which
revealed its spiral structure in
unprecedented detail.
See also: Astrophotography
118–19HENRY DRAPER
1837–1882A pioneer of astrophotography,
medical doctor Henry Draper
resigned as dean of medicine at
New York University in 1873 to
devote himself to astronomy. With
the assistance of his wife, Anna
Mary, Draper photographed the
transit of Venus in 1874, was
the first to capture the Orion nebula
on camera in 1880, and was also
the first to take a wide-angled
photograph of a comet’s tail in- He developed new techniques
for astrophotography, but died of
pleurisy in 1882, a few years before
DIRECTORY