Sky & Telescope - September 2020 - 9

ground but only considered Voyager 1's
motion relative to the Sun. The Voyagers nearly share the Sun's motion relative to the microwave background, so
neither the author nor the Voyagers are
being "left in the dust."
Nancy Morrison
Newton, Massachusetts

Dan Rinnan replies: Voyager 1 has
broken free of Earth's gravity, but it's
still within the gravitational frame of our Sun.
For a long time, it will share the Sun's motion through the Milky Way, and our galaxy's
movement through the universe itself. But in
about 40,000 years Voyager 1 will ﬂy within
1.6 light-years of AC+79 3888, a star in the
constellation Camelopardalis. The probe
may then be captured by that star's gravitational frame, and change direction, but
continue to orbit around the center of our
galaxy. So, yes, Voyager 1 shares my own
motion through space. But I've still traveled
a lot farther because, being older, I've had
33 years more travel time.

Photographing the Jet
I really enjoyed Howard Banich's "A
Curious Straight Ray" (S&T: Apr. 2020,
p. 30). It was interesting to read about
his visual impressions in instruments
over the impressive aperture range of
12 to 90 inches! I've also wondered
about the visibility of this object. I
decided to see how well it could be
photographed using a more modest
telescope. Last year, I tried my luck -
and succeeded - with my 6-inch f/9
Ritchey-Chrétien. Now, I wonder what
the smallest aperture capable of photographing this object would be?
Dave Billesbach
Lincoln, Nebraska

An Oldie But a Goodie
Last year, I required cataract surgery.
In my collection of old issues, I found
"Clearing the Clouds: Cataract Surgery

1970

1995

Allen Jensen
Ellijay, Georgia

FOR THE RECORD

* In the sidebar of "A Curious Straight Ray"
(S&T: Apr. 2020, p. 33), under "Making simplifications," the editors oversimplified, and
c is missing from the numerator of the first
equation's right side. It reappears, though,
in the solutions beneath.

SUBMISSIONS: Write to Sky & Telescope, One Alewife Center, Cambridge, MA 02140, USA or email: letters@
skyandtelescope.org. Please limit your comments to 250 words; letters may be edited for brevity and clarity.

75, 50 & 25 YEARS AGO by Roger W. Sinnott
1945

for Astronomers" by Kathy and Jerry Oltion (S&T: Sept. 2014, p. 34). The article
helped me navigate through the process
- eventually with a happy result.
I went through three different surgeons. The second did the cataract surgery, but my eyes had diffraction spikes
like the ones described in the article. My
third surgeon saw the issue and ﬁxed it.
Many thanks to S&T for an article
that is still relevant and available to
astronomers facing cataract surgery.

º September 1945
Novae as Yardsticks "In recent
years, the luminosities of new
stars have been established with
considerable accuracy, and our
knowledge of the absorption of
light in space has improved so
much that Dr. Dean B. McLaughlin, of the University of Michigan
Observatory, has made a study
of the space distribution for some
100 novae for which reasonably
good data are available. . . .
"The space co-ordinates of
these novae locate most of them
within 3,000 parsecs of the sun
and within about 500 parsecs of
the galactic plane. . . .
"[T]he Sagittarius novae are
at the distance of the star cloud
in that region of the sky. [But,
writes McLaughlin,] 'The present
investigation . . . gives no definite
answer to the question whether
the brightest star clouds in Sagittarius are truly parts of the central
nucleus of the galaxy.'"

º September 1970
Diffuse Interstellar Bands "The
spectra of distant, strongly reddened early-type stars often contain
certain broad, diffuse absorption
bands. . . . They clearly originate in
interstellar space, but the identification of the material causing these
absorptions has puzzled astronomers for decades.
"A startling but well-documented
identification was announced by
Fred M. Johnson, Electro-Optical
Systems . . . After a laboratory
survey of spectra of hundreds of
complex organic compounds, he
found that the diffuse interstellar
bands were closely matched by
bispyridylmagnesiumtetrabenzoporphine . . . How so complex a
molecule could be formed in interstellar space in large amounts is not
explained. Once formed, its survival
would be aided by its extreme
thermodynamic stability."
A century after the pioneering
work of William and Margaret Huggins, the analysis of deep-sky spectra was truly coming into its own.

º September 1995
Heavenly Brew "Ethyl alcohol, or
ethanol (CH3CH2OH) - the organic
compound that gives beer, wine,
and liquor their intoxicating powers - reveals itself . . . by emitting
discrete spectral lines at millimeter wavelengths. Although first
detected toward the galactic center
in 1975, ethanol has eluded subsequent searches of its expected habitat . . . Now, however, a British team
has located a huge reservoir of the
evasive compound on the outskirts
of a young star-forming region. . . .
"Thomas J. Millar [and two
colleagues] identified 14 spectral lines [betraying] ethyl alcohol
in the molecular cloud around
G34.3+0.15, a compact ionizedhydrogen region near the border
of Aquila and Serpens Cauda. The
features arise when an ethanol
molecule jumps between differing
quantum states of rotation. . . .
"[They] suggest that G34.3+
0.15's abundant ethanol is formed
on . . . the dust grains that cocoon
the system's newly formed stars."

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Sky & Telescope - September 2020

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