Sky and Telescope - January 2018 - 7

address (32 Myers Avenue, Bradford
BD2 4ET, England). The condition of
your issues is not paramount, though
they do have to be complete. Hopefully
I'll take them off your hands and give
them a good home.
Brian Jones
Bradford, England

A Special "Thank You"
I wish to thank David Levy for writing
Observing Variable Stars, which I first
read in 1992. That same year I joined the
American Association of Variable Star
Observers (aavso.org) and have been a
member every year since. Janet Mattei,
AAVSO's director at the time, mentored me back then, and I have enjoyed
observing variable stars to this day.
I might never have read Levy's book
had I not joined our local club, the
Indiana Astronomical Society, the previous year. Since then I've remained an
astronomy enthusiast generally, but I
can't think of any better way to contrib-

ute to the science of astronomy than to
observe variable stars.
Mark A. Bradbury
Greenwood, Indiana

1968

1993

Phil Petersen
League City, Texas

Seeing Double
A question occurred to me while reading "Eyes of the Dragon" (S&T: Aug.
2017, p. 22): Is there an official definition of an optical binary? In Matthew
Wedel's article, it seems that neither
magnitude nor separation is used in the
definition. The pairings in his list range
from 88.9 arcseconds apart (39 Draconis) to 15.4 arcminutes (Kappa Draconis). Yet all of the included pictures
show the potential for dozens of other
optical doubles (especially the illustration for 16 and 17 Draconis). Even
more confusing, the optical doubles he
highlights sometimes consist of two
stars with Flamsteed numbers, with a

"

Matt Wedel replies: If there's a
standard designation system for
optical doubles, it's news to me. If one could
see deeply or widely enough, almost every
star in the sky would appear surrounded by
potential optical companions. The criterion I
used in assembling the article's doubles was
simply, "Did they catch my eye?" I'd be curious to find out whether a more formal identification system for optical doubles exists.

FOR THE RECORD

* Due to production issues, a sketch of the
Orion Nebula (S&T: Dec. 2017, p. 37) came
out too dark. See the sketch in its full,
vibrant form at https://is.gd/HBM42.

SUBMISSIONS: Write to Sky & Telescope, 90 Sherman St., Cambridge, MA 02140-3264, USA or email: letters@
skyandtelescope.com. Please limit your comments to 250 words; letters may be edited for brevity and clarity.

75, 50 & 25 YEARS AGO by Roger W. Sinnott
1943

combination of Flamsteed and Draper
designations, or with one companion
having no official designation at all!

º January 1943
First Exoplanet? "The system
61 Cygni remains in the limelight,
owing to the interest of Dr. K. Aa.
Strand, of the Sproul Observatory.
Just a year ago he reported in this
magazine on the first successful
determination of the relative orbit of
[this] famous double star. . . .
"[Now he finds] small periodic
deviations [suggesting a third body
with] about 16 times the mass of
Jupiter, or 1/60 that of our sun. . . .
"Dr. Strand makes the suggestion that this invisible companion of
61 Cygni is a planet rather than a
star. If so, this is the first instance of
the discovery of planetary motion
outside our solar system. . . ."
Alas, this was the first of many
false alarms. A half century would
pass before astronomers confirmed
the first exoplanets in 1992.
º January 1968
Eyeball Insight "Nearly centered
on the visual axis of the human eye

is the shallow depression in the
retina known as the fovea. . . . [E]xperiments by George Wald of Harvard University show that the very
center of the fovea, its fixation area,
is blue-blind because practically
none of the numerous cones there
are blue sensitive. . . .
"Dr. Wald (co-winner of the
1967 Nobel prize in physiology)
advances an explanation for this
property of the eye:
"'Unable to develop a colorcorrected lens, the eye does the next
best thing, and through a number
of devices excludes or avoids using
the short-wavelength radiation that
would make the most trouble. . . .
"In the central retina, upon which
the eye most depends for pattern
recognition, the macular pigment
begins to absorb just where the lens
absorption falls off, and eliminates
much of the violet and blue.'"
º January 1993
Beyond Neptune "The solar
system got a little bit bigger last
autumn [when] David Jewitt (Uni-

versity of Hawaii) and Jane Luu
(University of California, Berkeley)
initially picked up the faint, 23rdmagnitude object on August 30th
while on patrol with a CCD camera
and the 88-inch reflector atop
Mauna Kea in Hawaii. . . .
"Confirmation of the discovery had to await the next dark of
the Moon. Jewitt returned to the
telescope on September 25th and
again found [the object, provisionally called] 1992 QB1. . . .
"Clearly, a solitary object in a
distant orbit is no proof that an
entire belt of material exists. But if
1992 QB1 does turn out to have a
circular or low-eccentricity orbit, it
will add considerable weight to the
Kuiper-belt hypothesis.
Author Paul R. Weissman (then
at NASA's Jet Propulsion Laboratory) cautiously tied 1992 QB1 to
the belt of icy planetesimals beyond
Neptune first envisioned by University of Chicago astronomer Gerard
P. Kuiper in 1951. Today more than
1,800 of these "trans-Neptunian
objects" are known.

sk yandtelescope.com * JA N UA RY 2 018

7


http://www.aavso.org https://www.is.gd/HBM42 http://www.skyandtelescope.com/

Sky and Telescope - January 2018

Table of Contents for the Digital Edition of Sky and Telescope - January 2018

Contents
Sky and Telescope - January 2018 - Cover1
Sky and Telescope - January 2018 - Cover2
Sky and Telescope - January 2018 - 1
Sky and Telescope - January 2018 - Contents
Sky and Telescope - January 2018 - 3
Sky and Telescope - January 2018 - 4
Sky and Telescope - January 2018 - 5
Sky and Telescope - January 2018 - 6
Sky and Telescope - January 2018 - 7
Sky and Telescope - January 2018 - 8
Sky and Telescope - January 2018 - 9
Sky and Telescope - January 2018 - 10
Sky and Telescope - January 2018 - 11
Sky and Telescope - January 2018 - 12
Sky and Telescope - January 2018 - 13
Sky and Telescope - January 2018 - 14
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Sky and Telescope - January 2018 - 16
Sky and Telescope - January 2018 - 17
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Sky and Telescope - January 2018 - 19
Sky and Telescope - January 2018 - 20
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Sky and Telescope - January 2018 - 82
Sky and Telescope - January 2018 - 83
Sky and Telescope - January 2018 - 84
Sky and Telescope - January 2018 - Cover3
Sky and Telescope - January 2018 - Cover4
Sky and Telescope - January 2018 - SGA18SAL
Sky and Telescope - January 2018 - 90
Sky and Telescope - January 2018 - SGA18S
Sky and Telescope - January 2018 - SGA18SA
Sky and Telescope - January 2018 - SGA18EAL
Sky and Telescope - January 2018 - 94
Sky and Telescope - January 2018 - SGA18E
Sky and Telescope - January 2018 - SGA18EA
Sky and Telescope - January 2018 - SGA18RAL
Sky and Telescope - January 2018 - 98
Sky and Telescope - January 2018 - SGA18R
Sky and Telescope - January 2018 - SGA18RA
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