Sky & Telescope - October 2020 - 7

scientists how far away they were created.
The depth is based on the wave frequency
and the shape of the signal.

Little Astronomers
It was a joy to see the photo of little
Calvin with the magazine in front of
him (S&T: June 2020, p. 6). It would
be interesting to see him at a telescope
a few years from now. I once tried to
give a 3½-year-old a look through my
telescope, but he couldn't hold his head
still enough to see anything. Six months
later, the reﬂexes in his neck and upper
body had matured enough that he could
get a good look at Saturn, and he said
that it looked like a spaceship.
Keith Brescia
Falls Church, Virginia

Confounding Particles
In his letter "A Twist of Terminology"
(S&T: June 2020, p. 7), Mark Trueblood
wonders what other astronomy terms
had been mixed up from one ﬁeld of

science using different terminology than
another. After training as a chemist, I
can testify that chemists refer to Mg(II)
as doubly ionized magnesium, whereas
astronomers deﬁne Mg II as singly
ionized magnesium. When I started
astronomy, I was deeply puzzled by H II
regions. How could a hydrogen atom
have lost two electrons?
Michel Bonnement
Courseulles-sur-Mer, France

Ludwig's Star
Johann Georg Liebknecht didn't give
the name Sidus Ludoviciana to the star
between Mizar and Alcor as stated in
Mathew Wedel's "The Horse and Rider"
(S&T: June 2020, p. 43). He named it
Sidus Ludovicianum and Stella Ludoviciana in two different publications. Both
names are Latin for "Ludwig's Star."
Sidus Ludoviciana is an ungrammatical

1970

1995

Michael Covington
Athens, Georgia

The Editors reply: This just goes

to show that our Latin is not what it
used to be. Another S&T gaffe that we promulgated is the deﬁnition of a Blue Moon,
traced back to our March 1946 issue. We
don't know whether to be ﬂattered or mortiﬁed that we have such inﬂuence.

FOR THE RECORD

* In "Ophiuchus Treasures" (S&T: July
2020, p. 45), the correct number of Messier
globular clusters in Sagittarius is seven.
* In "A Martian Sneak Peek" (S&T: June
2020, p. 48), the acronym ALPO stands
for the Association of Lunar & Planetary
Observers (alpo-astronomy.org).

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

mix of the two created by accident by
Joseph Ashbrook in "The Field of Mizar
and Alcor" (S&T: Apr. 1957, p. 265).

October 1945
Big Bang "In line with the trend
among popular science publications
to comment on the atomic bomb,
we must mention its relation to our
field of science. Theoretical astrophysicists talked about one superlatively great atomic bomb (although
not by that specific name) long
before the war lords even thought
of such a thing. It was the peaceloving Abbé Georges Lemaître, of
Belgium, who 15 years ago envisaged the explosion of one giant
primordial atom [that] produced the
widespread debris we observe as
the physical universe . . .
"The red shifts in the spectra of
the galaxies may be interpreted to
mean that these systems are receding from one another as they would
from a center of detonation."
Lemaître's concept of an
expanding universe slightly preceded that of Edwin Hubble, and
most astronomers now favor the
term Hubble-Lemaître Law.

October 1970
Uneclipsing Binary "The 9thmagnitude spectroscopic binary
HD 168206 in Serpens consists of a
Wolf-Rayet star and a B0 star, which
move around their center of mass
in a period of 29.6 days. The fact
that this binary is also an eclipsing system was discovered in 1949
by Sergei Gaposchkin on Harvard
patrol plates, [and it] became firmly
established in variable star literature
as CV Serpentis. . . .
"Recently, a special set of photometric observations was undertaken by L. V. Kuhi and F. Schweizer to determine the light curve
of CV Serpentis . . . Surprisingly,
there was no indication whatever
of variability! . . . The only explanation is that the system has stopped
eclipsing. Drs. Kuhi and Schweizer
suggest that the Wolf-Rayet envelope grew considerably during the
years 1963 to 1968. The expansion would make the envelope less
opaque, so at the time of primary
eclipse no appreciable dimming of
the B star would occur."

October 1995
Monster Comet "An inbound
10th-magnitude comet - first
spotted July 22nd by Alan Hale
and Thomas Bopp - may grow
to rival the Great Comet of 1811.
That's the guarded assessment of
Brian G. Marsden (Central Bureau
for Astronomical Telegrams),
whose orbit calculations place the
comet some 7 astronomical units
from the Sun at the time of its
discovery - beyond Jupiter and
farther out than any comet discovered by amateurs until now.
"Traveling in a plane perpendicular to the ecliptic, the comet
follows a highly elongated elliptical
path with an aphelion more than 10
times that of Pluto's orbit. In these
respects, as well as in its visibility
long before perihelion, Hale-Bopp
resembles the Great Comet of 1811,
whose tail grew to 70° and stretched
more than 1 a.u. in length."
Amateur astronomers would
not be disappointed with Comet
Hale-Bopp (C/1995 O1, see S&T:
July 2020, p. 30).

sk yandtelescope.org * OCTOBER 2 02 0

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Sky & Telescope - October 2020

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