Australian Sky & Telescope — November-December 2017

http://www.skyandtelescope.com.au 37

young man’s ability and seriousness of purpose, and he
continued to provide him with support.
Lacaille expected to become a priest. But he was smitten
with mathematics and astronomy, which he began to study
privately. He finished his theology degree but had no taste for
further religious study. Instead, as a self-taught astronomer,
in 1737 he obtained a recommendation for a position at the
Paris Observatory, which was then under the directorship
of Jacques Cassini, son of Jean-Dominique Cassini (the
discoverer of the Cassini Division in Saturn’s rings).
Here Lacaille honed his skills and applied them to the
science of geodesy. He helped map the French coast from
Nantes to Bayonne and took a leading role in remeasuring
the great meridian of France: the line of longitude from
the North Pole through Paris to the equator. The precision
surveying for this project verified earlier work showing
that Earth is an oblate spheroid — slightly wider across
the equator than from pole to pole — rather than a prolate
spheroid as some had argued.
Lacaille’s work gained him election to the Royal Academy
of Sciences in Paris and a post at the Collège Mazarin.
There he established a small observatory, made systematic
observations of star positions and parallaxes, and wrote
widely read texts on mathematics, astronomy and optics. By
the late 1730s he had established a solid reputation and a
comfortable future as an academic.
But he sought new challenge, and he found it in the
southern skies. He proposed to the Academy that he make
an expedition to the Cape of Good Hope to catalogue the
southern sky and to make geographical measurements of the
region. On November 21, 1750, Lacaille embarked on the
ship Glorieux, heading first to Rio de Janeiro, then tacking
east to South Africa.
On April 19, 1751, Lacaille landed at Cape Town, then
a small way station of the Dutch East India Company.
Carrying a letter of introduction from the Dutch Prince of
Orange, he was received warmly by the Dutch governor and
obtained lodging at the home of Jan Bestbier on what is now
Strand Street.
The Dutch found the French astronomer somewhat
reserved but amiable, and they gave him what help and
materials they could. In the backyard of Bestbier’s home,
Lacaille oversaw the construction of a 12-foot-square
observatory for his instruments and telescopes, which included
a 14-foot-long refractor for timing the phenomena of Jupiter’s
moons: their eclipses and their entries and exits across
the planet’s face. The local times of these events, carefully
determined, could be compared against the local times
predicted for the events at the longitude of Paris or London,
yielding a means to determine one’s longitude anywhere in the
world — ingenious, though fairly crude in practice.

WREPORTING BACK The Starry Southern Sky was Lacaille’s initial
report to the astronomical world after he returned to a hero’s welcome in
France. It included measures of only the brightest southern stars.

FORNAX

Lacaille’s constellations

◗^ Born into the Age of Reason, the industrious and

serious-minded Lacaille mostly shunned fanciful names

for his new constellations. Instead, he filled his sky with

tools of the arts and sciences. Most of the bright southern

stars had already been assigned to constellations by

Petrus Plancius and Johann Bayer in the late 16th and

early 17th centuries, so Lacaille’s 14 new constellations

are quite dim. They were the last ones created that are

still in use today

Here they are with their current, often shortened,

names, and their meanings and the original French

names on Lacaille’s first edition of his southern sky map.

Antlia, the Air Pump (la Machine Pneumatique)

Caelum, the Engraver’s Tools (les Burins)

Circinus, the Geometer’s Compass (le Compas)

Fornax, the Chemist’s Furnace (le Fourneau)

Horologium, the Pendulum Clock (l’Horloge)

Mensa, Table Mountain (Montagne de la Table)

Microscopium, the Microscope (le Microscope)

Norma, the Carpenter’s Square (l’Équerre et la Règle)

Octans, the Octant (l’Octans de Réflexion)

Sculptor, the Sculptor’s Workshop (l’Atelier du Sculpteur)

Pictor, the Painter’s Easel (le Chevalet et la Palette)

Pyxis, the Mariner’s Compass (la Boussole)

Reticulum, the Eyepiece Reticle (le Réticule Rhomboïde)

Telescopium, the Telescope (le Télescope)

In addition, Lacaille divided huge Argo Navis, a survival

from classical times, into three:

Puppis, the Stern

Carina, the Keel

Vela, the Sails

It’s no wonder that astronomer Heber Curtis of Lick

Observatory remarked that, when he first saw a map of

the far-southern sky, “It looked like somebody’s attic”.