Sky and Telescope - May 2018 - 45

Under the Stars by Fred Schaaf

In the Path of the
Closest Comet
From Draco to Cancer a comet hurtled.
"The closest - and I do mean closest -
thing that anyone alive has ever seen
to a comet's colliding with Earth I saw
outstandingly well in 1983."
- Fred Schaaf, Comet of the Century

AUR A / K PN O

hirty-ﬁve years ago this month I
got some of the best weather in the
world to help me experience a prodigious wonder most skygazers missed.
It was the nearest pass to Earth of a
comet in over 200 years. The marvel
was Comet IRAS-Araki-Alcock (Comet
I-A-A), discovered ﬁrst by the Infrared Astronomical Satellite and then
independently by amateur astronomers
Genichi Araki in Japan and George
Alcock (with binoculars out a window)
in England.
I spent six nights following this
intrinsically dim comet through ever
brighter and bigger forms as it hurtled
less than 3 million miles from Earth.
Its path across the stars on those nights
is one I'll never forget - and one which
I'd like to explore in its own right here
in this column. All of the following

quotes are from my book Comet of the
Century (Copernicus Books, 1996).
First night: Naked eye past
Draco's head. "My search with binocs
immediately produced a prominent ball
of fuzzy light in its still imperceptibly
slow roll past the head of the celestial
dragon." When I ﬁrst spotted Comet
I-A-A, it was a roughly magnitude-4.9
object detectable with the naked eye,
with a 15′ patch of coma visible in a
6-inch telescope.
The circumpolar head of Draco
doesn't get highest in the north until
the middle of a May night but is already
prominent in the northeast in the
evening. The Dragon's head points
toward ascending Vega and the Keystone of Hercules. It consists of stars
of 2nd, 3rd, 4th, and 5th magnitude:
Gamma (γ) Draconis (Eltanin), Beta
(β) Draconis (Rastaban), Xi (ξ) Draconis (Grumium), and Nu (ν) Draconis
(Kuma). Eltanin, at 2nd magnitude, is
the orange eye of Draco. And 5th-magnitude Kuma is formed by equally bright
white components a generous 62″ apart.

Third night: A Great Orion Nebula
in the body of Draco. "Last torn cloud
curtain edge was withdrawn to reveal a
sky clean and sheer to about mag. 7.0 at
its summit . . . and a handful of strong
phosphorescence hung in mid-ﬂight on
that sky's north shoulder." The comet
was in the long, twisting body of Draco,
which wraps around the North Ecliptic
Pole, near which glows NGC 6543, the
wonderful 9th-magnitude Cat's Eye
Nebula. But that night Comet I-A-A
appeared larger and much brighter than
M8, the Lagoon Nebula, like a detached
piece of Milky Way, ". . . or at least
for me in that magic clear dark - like
another Orion Nebula in size, brightness and even shape!"
Fourth night: Flung from the
Little Dipper's bowl. At nightfall the
comet's coma was already surrounding
Kochab, Beta (β) Ursae Majoris. "It was
fascinating viewing the rather bright
star cloaked in that slight veil, and
the conjunction of the comet's center
with the star was surprisingly close."
The comet was going so fast it only
took minutes for it to move off of this
underappreciated orange "Guardian of
the Pole" that's very nearly as bright as
Polaris. It was seemingly being ﬂung, in
one day, from the Little Dipper's bowl
to just past the Big Dipper's bowl. I
judged the comet to be magnitude 2.8
or 2.9 and 1° to 1¼° wide to the naked
eye that night.
Sixth night: A huge, near-1stmagnitude comet passes M44. The
head of the comet was very close to
the smaller, much dimmer patch of
M44 (the magnitude-3.1 and 1½°-wide
Beehive Cluster). Comet authority John
Bortle rated the comet's head as magnitude 1.7 and at least 2° wide that evening. Walter Scott Houston estimated
the comet's head as an astounding 6°
across! And, in a sky so dark and clear
I could trace the zodiacal light bridge
across it, I saw the two edges of the
previously tailless comet's tail extending up to 15° long.
¢ FRED SCHAAF saw his first nakedeye comet, Tago-Sato-Kosaka, in 1970
- just before seeing Comet Bennett.
s k y a n d t e l e s c o p e . c o m * M AY 2 0 1 8

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Sky and Telescope - May 2018

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