CHAPTER ONE continued...
Although the Arabs increased the number of
star names, the number of constellations remained unchanged.
The first extension of Ptolemy’s 48 was made in 1536 on a
celestial globe by the German mathematician and cartographer
Caspar Vopel (1511–61) who depicted Antinous and Coma
Berenices as separate constellations; in the Almagest, Ptolemy had
mentioned these groups as sub-divisions of Aquila and Leo
respectively. His lead was followed in 1551 on a celestial
globe by the great Dutch cartographer Gerardus Mercator. The
great Danish astronomer Tycho Brahe listed Antinous and Coma
Berenices separately in his influential star catalogue of 1602,
ensuring their widespread adoption. Coma Berenices is still a
recognized constellation, but Antinous has since been remerged
with Aquila.
By now the age of exploration was well
under way and navigator–astronomers turned their
attentions to the hitherto uncharted regions of the sky in the
southern hemisphere that had been below the horizon for the
ancient Greeks. Three names stand out from this era. The first
is Petrus Plancius (1552–1622), a Dutch theologian and
cartographer; his name is the Latinized form of Pieter
Platevoet (literally, Peter Flatfoot). The other two were the
Dutch navigators Pieter Dirkszoon Keyser (c.1540–96), also known
as Petrus Theodorus or Peter Theodore, and Frederick de Houtman
(1571–1627). Surprisingly, all three are little-known
today despite their lasting contributions.
Plancius instructed Keyser to make
observations to fill in the constellation-free zone around the
south celestial pole. Keyser was chief pilot on the Hollandia and later on
the Mauritius, two of the fleet of four ships that left the
Netherlands in 1595 on the first Dutch trading expedition to
the East Indies, sailing via Madagascar. Keyser was adept at
astronomy and mathematics; the Dutch author A. J. M. Wanders,
in his book In the Realm of the Sun
and Stars, writes that Keyser
observed from the crow’s nest with an instrument
(probably an astrolabe or cross-staff – this was still
the pre-telescopic era) given to him by Plancius. Keyser died
in September 1596 while the fleet was at Bantam (now Banten,
near the modern Serang in western Java). His catalogue of 135
stars was delivered to Plancius when the fleet returned to
Holland the following year. Regrettably, little else seems to
be known about the life and accomplishments of Keyser, but he
left his mark indelibly on the sky.
Keyser’s stars, divided into 12 newly
invented constellations, first appeared on a globe by Plancius
in 1598, and again two years later on a globe by the Dutch
cartographer Jodocus Hondius. The acceptance of these new
constellations was assured when Johann Bayer, a German
astronomer, included them in his Uranometria of 1603, the leading
star atlas of its day. Keyser’s observations were
published in tabular form by Johannes Kepler in the Rudolphine Tables of
1627. Unfortunately, Keyser’s original manuscript is long
lost and so we do not know whether he sorted his stars into the
12 new southern constellations himself or whether that was done
later by someone else, such as Plancius.
The Dutch fleet in which Keyser sailed was
commanded by the explorer Cornelis de Houtman; among the crew
was his younger brother Frederick de Houtman who apparently
assisted Keyser in his observations. On a second expedition in
1598 Cornelis was killed and Frederick was imprisoned by the
Sultan of Atjeh in northern Sumatra. Frederick made good use of
his two years in prison by studying the local Malay language
and making astronomical observations.
In 1603, following his return to Holland,
Frederick de Houtman published his observations as an appendix
to a Malay and Madagascan dictionary that he compiled –
one of the most unlikely pieces of astronomical publishing in
history. In the Introduction he wrote: “Also added [are]
the declination of several fixed stars which during the first
voyage I have observed around the south pole; and during the
second [voyage], in the island of Sumatra, improved upon with
greater diligence, and increased in number.”
De Houtman increased Keyser’s 135
measured star positions to 303, although 107 of these were
stars already known to Ptolemy, according to a study of the
catalogue by the English astronomer E. B. Knobel. Nowhere did de Houtman give Keyser credit for
his priority (in fact, the two men seem not to have been on
good terms, despite their common interest in the sky). De
Houtman’s catalogue of southern stars, divided into the
same 12 constellations as shown on the globes by Plancius and
Hondius, was used by the Dutch cartographer Willem Janszoon
Blaeu for his celestial globes from 1603 onwards. Keyser and de
Houtman are now credited jointly with the invention of these 12
southern constellations, which are still recognized today (see Table 2). However,
the Dutch historian Elly Dekker has argued that the true credit
for dividing the newly observed stars into 12 constellations is
actually due to Petrus Plancius, after he received
Keyser’s catalogue in 1597.
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Whatever the case, Plancius invented some
constellations that are indubitably his own, among them
Columba, the dove, which he formed from nine stars that Ptolemy
had listed as surrounding Canis Major; he also invented the
unlikely sounding Monoceros, the unicorn, and Camelopardalis,
the giraffe, from faint stars uncharted by Ptolemy. These three
Plancius constellations are still accepted by astronomers, but
his other inventions fell by the wayside (see Chapter
Four).
© Ian Ridpath. All rights reserved
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