Sky & Telescope - November 2020 - 59

The Strange Case of

Comet Biela
O

ur story begins with Isaac Newton and his law of
universal gravitation. The theory put all motion in
the solar system under a single mathematical law, one
that possessed a high degree of precision. It worked for the
planets and their satellites. Soon after Newton published his
theory, some wondered if it applied to those singular, ﬂeeting
objects, comets.
Among those who thought it did was
a younger contemporary of Newton's,
Edmond Halley. In his 1705 paper "A Synopsis of the Astronomy of Comets," Halley
wrote that comets observed in 1531, 1607,
and 1682 all had very similar orbits, and he
declared that they were all the same object
returning every 76 years. He predicted its
return in 1758. Halley died in 1742, so he
didn't get to see this icy body again. But
astronomers honored his discovery of the
ﬁrst comet known to be a member of the
solar system by giving his name to it.
In 1819, the German astronomer Johann
Franz Encke calculated the orbit of a comet
that was also found to coincide with several
others. In doing so, he had discovered the
second comet identiﬁed as periodic. As with
Halley's Comet, this one, ofﬁcially known as 2P/Encke, was
named after Encke and not after the astronomer who'd ﬁrst
observed and reported it - Pierre Méchain, in 1786.
There matters stood for seven years.

It vanished, then returned,
then vanished again, only
to possibly return anew.
What gives?

military ofﬁcer named Baron Wilhelm von Biela.
Biela was born in 1782 in what is now northern Germany.
Not much is known about his early life, but in 1802 he joined
the Austrian army, and because he was an aristocrat he was
made an ofﬁcer. Biela later served in several campaigns in
the war against Napoleon. Astronomy apparently was not an
abiding interest of his until 1815, when he
began a study of the subject in Prague under
the Bohemian clergyman and astronomer
Alois Martin David. Still, Biela kept his day
job. He was in eastern Bohemia, stationed at
Fort Josefov, when he made his discovery.
On the night of February 26, 1826, Biela
observed the comet that would come to
bear his name. It was faint enough to be
visible only in a telescope. He calculated
the comet's orbit and found it to be an
ellipse with a 6.6-year period. The French
astronomer Jean-Félix Adolphe Gambart
independently discovered the same comet a
short time later. Gambart also calculated its
orbit and managed to link this comet with
another seen in 1805. This made Biela's
Comet, ofﬁcially designated 3D/Biela, only
the third comet determined to be periodic.
(In subsequent decades, some astronomers, particularly in
Gambart's home country of France, felt that his name should
have been attached, perhaps even solely, to the comet. But
Biela's Comet it remains.)
It might seem unusual today for an amateur to both
observe and do calculations, but it was not so back then.
Professional astronomers busied themselves with cataloging
precise positions of the stars and planets, to determine such
things as ships' positions on Earth. They were not observers
of the heavens for the love of it. Thus, most discoveries fell
to amateurs. The Herschels - William, Caroline, and John
- were perhaps the best known. William, for instance, was
not a professional astronomer but a musician and composer
when he discovered Uranus (in 1781) and conducted his ﬁrst
and second all-sky surveys. In those days there was no place
an amateur could go to calculate cometary orbits from obser-

Astronomers
gave up on ever
laying eyes on
either piece of the
comet again. But
stories of Comet
Biela's demise
were premature.

Discovery!

SPL / SCIENCE SOURCE

In the 18th and early 19th centuries, most observational
work was done by amateur astronomers. (Even today, amateurs are deeply involved in regularly monitoring comets,
asteroids, variable stars, and other celestial objects.) In the
early 1800s, one of those amateurs was a German-Austrian
t A DAZZLING SPECTACLE When Earth passed through the dusty tail
of Comet Biela on the night of November 27, 1872, Europeans out that
night enjoyed one of the finest meteor showers in recorded history, as
depicted in this period illustration.

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Sky & Telescope - November 2020

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