Sky & Telescope - November 2020 - 64

Cometary History

In succeeding years, the Andromedid
meteors periodically reappeared,
though they never again rose to the
spectacular level seen in 1872.
from near the star Gamma (γ) Andromedae, so they're called
the Andromedids (see sidebar on page 63).
Astronomers tried to ﬁgure out what caused this tremendous display. Eventually they determined that, because Earth
had passed very close to the comet's orbit that night, our
planet likely traveled through dust from the comet's tail that
had been emitted during the frozen body's previous passages
through the inner solar system. This was one of the ﬁrst
instances in which a comet's debris ﬁeld was tied to an exceptional meteor storm.
So, long after astronomers had given it up for lost, Comet
Biela had returned, in a way, to give one more show. It was a
display that was far more impressive than the comet itself had
ever been.
In succeeding years, the Andromedid meteors periodically
reappeared, though they never again rose to the spectacular
level seen in 1872. The Andromedids continued to decline
until they, like their parent body, pretty much disappeared.
That should have been the end of the story. But it wasn't.

Comet Biela, Where Are You?
In the late 1960s, Brian Marsden, best remembered for
his long tenure as director of the Minor Planet Center at
the Harvard-Smithsonian Center for Astrophysics, used

Andromedid Meteor Shower
CASSIOPEIA
Capella

C E P H EU S

P E RS
R EUS
Andromedid
radiant

10°

Algol

ANDROMEDA

computers to ﬁnd lost comets and
asteroids. Comet Biela was one of
those he tackled.
Marsden began by assuming that
the nucleus of the smaller of the
separated pair had disintegrated
completely, so he concentrated on
the bigger fragment. Assuming the
non-gravitational forces (that is, jets)
had ceased after the last conﬁrmed
p BLAZING SADDLE
Comet Kohoutek apsighting in 1852, he calculated the
pears in this false-color,
position for this object and found that
far-ultraviolet image
it would reach perihelion on Decemtaken during a Skylab
ber 21, 1971, at a distance of only
spacewalk on Christ0.05 astronomical unit from Earth,
mas Day, 1973.
or roughly 7.5 million kilometers
(4.6 million miles).
Astronomers searched for this fragment, but they observed
only a few very faint asteroids, which they were never able to
connect to Comet Biela.
However . . . .
One of the searchers was Czech astronomer Luboš
Kohoutek, who used the 800-mm (31.5-inch) Schmidt
camera at the Hamburg Observatory. In his hunt Kohoutek
discovered a comet. Amateurs active in the early 1970s will
remember that Comet Kohoutek, formally designated C/1973
E1, was predicted to become bright enough to be seen with
the naked eye, and it rocketed to fame. But when it failed
to fulﬁll its predicted promise, it became quite infamous.
Through Comet Kohoutek's fate, it seemed vaguely as if Wilhelm von Biela's comet had reared its head again.
Two other comets have orbits similar to Comet Biela's, and
a few astronomers have tried to ﬁnd a link between them and
the baron's comet. The ﬁrst is Comet 18D/Perrine-Mrkos,
originally discovered in 1896. Its orbit is similar to Biela's save
for the argument of perihelion, the orientation of the comet's
orbit around the plane of the ecliptic, so most astronomers
don't accept it as a match for Biela's Comet. Oddly enough,
this intrinsically faint comet has also been lost; it was last
seen in 1969. The second suspect is Comet 207P/NEAT
(P/2001 J1), discovered in 2001 by the NEAT asteroid survey.
But again, astronomers have not been able to establish a connection to Biela's Comet.
So, whether Comet Biela is truly lost or just frustratingly
elusive remains to be seen.

¢ DAVE NAKAMOTO has been an amateur astronomer for
more than 50 years. His most recent article for S&T is "The
Enigma That Is BL Lacertae" (S&T: Sept. 2018, p. 30).

TRIANGULUM

P E G AS U S

p On December 2, 2023, the Andromedids "might yield as many as 200
meteors an hour, surpassing the Perseids and Geminids," according to
Paul Wiegert and colleagues. As Joe Rao notes, "Mark your calendars!"

NOVEMBER 2 02 0 * SK Y & TELESCOPE

FURTHER READING
"The Return of the Andromedids Meteor Shower," by Paul
A. Wiegert, Peter G. Brown, Robert J. Weryk, and Daniel K.
Wong. The Astronomical Journal, Vol. 145, No. 3, March 2013:
https://is.gd/Andromedids

N ASA

ARI ES

https://www.is.gd/Andromedids

Sky & Telescope - November 2020

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