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Flamsteed numbers –
where they really came from
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FLAMSTEED NUMBERS are the numerals attached to stars in a constellation for
identification purposes, such as 61 Cygni or 51 Pegasi. They are named after
the English Astronomer Royal John Flamsteed (1646–1719), who produced the first major star catalogue made with the aid of a
telescope, published posthumously in 1725. It is often assumed that the
so-called Flamsteed numbers were assigned to the stars by Flamsteed himself,
but that is not the case. Flamsteed’s published catalogue contained no such numbering system. So where did they come from?
The American historian Deborah Jean Warner seems to have been the first to point
out that the numbers we now use were actually allocated by a French astronomer,
Joseph Jérôme de Lalande (1782–1807). They appeared in a revised edition of Flamsteed’s catalogue published in 1783 in a French almanac, Éphémérides des mouvemens célestes. In this French edition, Lalande numbered Flamsteed’s stars consecutively by constellation. This is the numbering system we now know
as “Flamsteed numbers”. The illustration below shows an example from the first page of Lalande’s edition. Click on it for an enlargement.
Although there were no Flamsteed numbers in Flamsteed’s own catalogue, Flamsteed did include columns with the order of appearance of
each star in the catalogues of Ptolemy (the Almagest) and Tycho Brahe, plus a third column with the Greek letters assigned by Johann
Bayer (the so-called Bayer letters). These columns were repeated by Lalande in his French edition. In the example
below, the abbreviation “inf” in the Ptolemy column refers to the so-called informatae, or unformed, stars that Ptolemy regarded as lying outside the constellation
figure proper. The star referred to here is the one we know as Alpha Arietis,
the brightest star in the modern Aries. Despite its brightness, Ptolemy decided it did not fit the constellation
figure. Instead, he placed it among the informatae.
Above: The first page of J. J. Lalande’s edited and corrected version of John Flamsteed’s star catalogue, published in 1783. The stars shown here belong to the constellation Aries. In the first column, Lalande numbered each star consecutively by constellation. These are the numbers that we now call Flamsteed numbers. There was no such column in Flamsteed’s original catalogue. Click on the illustration for an enlargement of the page, or click here to see the whole of Lalande’s edited catalogue. |
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