Sky & Telescope - November 2020 - 7

myself an amateur astronomer. Much
of what I read in S&T ﬂies past me as
Halley's Comet did the year she was
born, but Ashley Davies' article "Io, the
Volcanic Rosetta Stone" (S&T: July 2020,
p. 14) was so wonderfully written and
illustrated that I ﬁnally understood a
few of the basic tenets of tidal heating.
Congratulations and thank you for this
revelation of outer-space phenomena
and for bringing an aging adult wonders
of science and physics that were largely
unknown back in my day, when we had
nine planets. I'm hoping to stick around
long enough to make up for a good portion of what I've missed, proudly wearing
my "Never Underestimate an Old Man
Who Loves Astronomy" T-shirt.

Across an Eclipse

question. Low-mass stars do create
heavy elements through neutron capture,
in a gentler process than fusion called the
s-process (s is for slow). As the star ages,
reactions in the star create free neutrons,
and these combine with heavy atoms left
over from previous generations of stars.
When this reaction creates unstable nuclei,
the neutrons decay into protons, creating
heavier elements. Margaret Burbidge and
colleagues wrote the seminal work that ﬁrst
described the formation of heavy nuclei in
1957: https://is.gd/Margaret_Burbidge.
The periodic table we published is a reproduction of the one published by Jennifer
Johnson in the research journal Science last
year: https://is.gd/Nucleosynthesis.

Io Epiphany

John P. Junke, Sr.
Walla Walla, Washington

2020, p. 49), SAO 188414 was mislabeled
as SAO 1888414.

My daughter gave me a gift subscription to Sky & Telescope in 2018. I have
some basic equipment but don't consider

SUBMISSIONS: Write to Sky & Telescope, One Alewife Center, Cambridge, MA 02140, USA or email: letters@
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Camille Carlisle replies: Great

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

1970

1995

º November 1945
Radar's Novelty "War-inspired
advances in electronics promise to
[be of value to] astronomers.
"Radar-tracking equipment
may ultimately perform highly
accurate parallax work in the solar
system. The time interval required
for a radio pulse to be reflected
back from a distant object tells the
distance . . . and the accuracy in
distance attainable promises to be
of the order of a fraction of a mile!
Moreover, as the character of the
echo depends on the nature of the
reflecting surface, radio ranging might eventually answer such
questions as, for example, whether
or not there are oceans on Venus."
The ﬁrst hint that Venus is too
hellishly hot for oceans came in
the 1950s, not from radar, but
from the planet's emission at radio
wavelengths. Crude radar mapping of the cloud-veiled surface
from Earth began in the 1960s, but
it vastly improved later, close up,
with the Soviet Venera and American Magellan orbiters.

The photograph of an airplane crossing
the partially eclipsed Sun below Howard Ritter's letter (S&T: Aug. 2020, p.
6) is an illustration of a phenomenon I
have seen many times since becoming
a solar observer in 1979.
I mentioned one of these sightings
while giving a talk on solar observing
to the Memphis Astronomical Society
several years ago. My friend Richard
Moore immediately declared it the
"Plane of the Ecliptic."
Bill Wilson
Memphis, Tennessee

FOR THE RECORD

* In the "Path of Pluto" chart (S&T: July

º November 1970
Nonrandomness? "[Typically,
meteor-shower watchers] see some
meteors coming in quick succession, others separated by long intervals. . . . The existence of bunchiness cannot be accepted as real
unless it meets a suitable statistical
test, such as the following.
"At Running Springs, California,
John Rabold and David Gilmore
used a tape recorder and WWV
signals to obtain the arrival times
of Perseids to the nearest second
on the morning of August 12th. Let
us take their data for the two-hour
period beginning at 9:00:00 UT,
during which 155 Perseids were
recorded. We divide this period
into 120 consecutive intervals of
60 seconds each, and count how
many intervals contain 0 meteors,
1 meteor, 2 meteors, and so on.
[An accompanying table compares
these to] the Poisson distribution formula . . . The agreement
between the observed and predicted values . . . is so close that
we can infer a random distribution
of arrival times, at least for this
sample of 155 Perseids."

Editor Joseph Ashbrook often
engaged readers in useful observing projects, then demonstrated
their scientiﬁc value.
º November 1995
Space Voids "Bubbles, supershells, and chimneys - vast regions
nearly empty of interstellar gas
- can be found in many galaxies
[including the Milky Way.
"In fact,] data obtained at
ultraviolet wavelengths suggest
that our solar system may enjoy
a chimney of its own. Spectral
studies of the yellow giant star 31
Comae with the Extreme Ultraviolet Explorer satellite show remarkably little absorption of the star's
emission by ionized magnesium
and atomic hydrogen. A typical
swath of the interstellar medium
contains enough of these two
gases to create strong absorption lines in a star's spectrum.
This suggests, noted Thomas R.
Ayres (University of Colorado) and
his colleagues, that we may be
looking out a 'hole,' or chimney,
when viewing perpendicular to the
galactic plane."

sk yandtelescope.org * NOVEMBER 2 02 0

https://is.gd/Margaret_Burbidge https://is.gd/Nucleosynthesis https://skyandtelescope.org/

Sky & Telescope - November 2020

Table of Contents for the Digital Edition of Sky & Telescope - November 2020