CHAPTER ONE continued...
Extending Ptolemy’s 48
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.
Scouting the southern sky
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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THE CONSTELLATIONS OF
PETRUS PLANCIUS
Petrus Plancius (1552–1622), Dutch cartographer and constellation inventor.
(University of Amsterdam)
PETRUS PLANCIUS left no written records so what we know of his role in the
development of our system of constellations is based on examination of his
surviving maps and globes.
His first foray into celestial mapping came on a terrestrial map of 1592 which
contained small insets in the top corners showing the northern and southern
sky. Among the constellations were two inventions of his own: Columba, the
dove, and Polophylax, a pole-watcher, intended as the southern equivalent of Boötes (which the Greeks termed Arctophylax or bear-watcher). Columba, formed from
stars known to Ptolemy south of Canis Major, became established. Polophylax,
based on sketchy information about the southern stars and positioned between
Piscis Austrinus and the southern pole in an area now occupied by Grus and
Tucana, did not.
In 1598, Plancius produced a globe in conjunction with Jodocus Hondius that was
a landmark in constellation history. For the first time 12 new southern
constellations were shown, based on the catalogue of Pieter Dirkszoon Keyser
which had been brought back from the East Indies in 1597 after Keyser’s death. The slightly later and more extensive catalogue of the same
constellations by Frederick de Houtman was used by Willem Janszoon Blaeu, a
rival to Plancius.
A later Plancius globe of 1612 introduced Camelopardalis and Monoceros, along
with others in both hemispheres that never gained acceptance: Jordan, Tigris,
Apes (= Musca Borealis), Gallus, Cancer Minor, and Sagitta Australe.
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FREDERICK DE HOUTMAN’S CATALOGUE
Dutch constellation inventor.
THE oldest surviving catalogue of the southern stars was made by the Dutch
seafarer Fredrick de Houtman (1571–1627) from Sumatra and published in Amsterdam in 1603. Only about half a dozen
remaining copies are known, one of them in the Bodleian Library, Oxford. A
facsimile of it was privately published in 1927 by the British astronomers H.
H. Turner and E. B. Knobel.
In his catalogue, de Houtman lists 304 stars, although coordinates are not given
for one of them (in the tail of Scorpius). In his Introduction to the
dictionary, de Houtman states that he made some observations of the southern
stars on his first voyage in 1595–97, and revised and increased the number on his second voyage, 1598–1602. How much of de Houtman’s work was copied from his countryman Pieter Dirkszoon Keyser (c.1540–96), who did not survive the first voyage, remains open to speculation.
The 12 new constellations listed by de Houtman, with their present-day names in
brackets, are as follows: Den voghel Fenicx (Phoenix); De Waterslang (Hydrus);
Den Dorado (Dorado); De Vlieghe (Musca); De vlieghende Visch (Volans); Het
Chameljoen (Chamaeleon); Den Zuyder Trianghel (Triangulum Australe); De
Paradijs Voghel (Apus); De Pauww (Pavo); De Indiaen (Indus); Den Reygher – literally “the heron” (Grus); Den Indiaenschen Exster, op Indies Lang ghenaemt – literally “the Indian magpie, named Lang in the Indies” (Tucana). In addition, he listed stars in the pre-existing constellations of
Ara, Argo Navis, Centaurus, Corona Australis, Crux, Lupus, Columba (which he
called De Duyve met den Olijftak – literally “The dove with olive branch”), the tail of Scorpius, and southern Eridanus, which he termed “den Nyli”, the Nile.
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