79
See also: Consolidating knowledge 24–25 ■ The southern hemisphere 100–01F
rench astronomer and
mathematician Nicolas-
Louis de Lacaille had the
idea to use trigonometry to measure
the distance to the planets after
observing them from different
places. To provide the longest
possible baseline for his calculations,
Lacaille needed simultaneous
observations in Paris and at the
Cape of Good Hope. To this end,
he traveled to South Africa in
1750 and set up an observatory
at Cape Town. There, he not only
observed the planets, but also
measured the positions of 10,000
southern stars. His results were
published posthumously in 1763
in Coelum Australe Stelliferum.
They proved to be his greatest
legacy to astronomy.Southern stars
Parts of the sky surveyed by Lacaille
are too far south to be visible from
Europe and many of the stars he
observed had not been allocated to
constellations. To give designations
to the stars in his catalog, Lacaille
introduced 14 new constellationsthat are still recognized and used
today, and he defined the boundaries
of existing southern constellations.
Before leaving South Africa, he also
carried out a major surveying project
with the aim of better understanding
the shape of the Earth.
Lacaille was a zealous and
highly skilled observer who
appreciated the value of accurate
measurements. He demonstrated
an exceptional ability and energy
to pioneer a thorough survey of
the southernmost sky. ■THE TELESCOPE REVOLUTION
A CATALOG
OF THE
SOUTHERN SKY
MAPPING SOUTHERN STARS
IN CONTEXT
KEY ASTRONOMER
Nicolas-Louis de Lacaille
(1713 –1762)
BEFORE
150 ce Ptolemy lists the 48
constellations that can be seen
from Mediterranean latitudes.
1597 Petrus Plancius, a
founder of the Dutch East
India Company, uses the
findings of explorers Keyser
and de Houtman to introduce
12 new southern constellations
on his celestial globes.
c.1690 Prodomus Astronomiae,
by Polish astronomer Johannes
Hevelius, names seven new
constellations still in use.
AFTER
1801 Johann Bode’s
Uranographia, a collection of
20 star maps, is the first near
complete guide to stars that
are visible to the naked eye.
1910 School master Arthur
Norton produces his star atlas,
which is popular for a century.
Lacaille laid the
foundation of exact
sidereal astronomy in the
southern hemisphere.
Sir David Gill