Sky & Telescope - December 2023 - 7

I've seen many photographs of M7
since then, but there is nothing like
" simple, " live viewing. The image has
stayed in my mind. The same was true
when I first found M41 with binoculars.
And even more so when, unlooked
for, I happened to discover M38, M36,
M35, and M37 - clusters I didn't even
know about - appearing like a stairway
to heaven, with a thrill that is difficult
to express. Observation becomes
contemplative joy.
Clyde Glandon
Tulsa, Oklahoma
Calling All Historians
Thank you so much for Dennis di
Cicco's excellent article " Stellafane Turns
100 " (S&T: Aug. 2023, p. 60) about the
centennial celebration of the Springfield
Telescope Makers this year. At the
2023 Stellafane Convention, we featured
numerous historical artifacts and
photos, but we are seeking to expand our
collections from Stellafane's past. We
have a special request for the astronomy
community to help us with our ongoing
Stellafane history project. If anyone has
old photos or other artifacts from Stellafane's
past that they would like to share
with us, they can reach out to us at history@stellafane.org.
We look forward to
seeing old friends and meeting new ones
on Breezy Hill throughout the year, just
as Russell Porter and his fellow explorers
of the universe did 100 years ago.
Cecilia Detrich
Vice President
Springfield Telescope Makers
Nahant, Massachusetts
FOR THE RECORD
* In " The Past and Future of Star Names, "
the name Achernar (S&T: May 2023, p. 31)
comes from akhir al-nahr (River's End).
* In " What Is a Spectrum? " (S&T: Sep.
2023, p. 74), the base of a candle flame
isn't bluer because it's hotter. While the
orange part of candle flames can indeed
be treated as blackbody emitters, the blue
base of a flame comes from chemical reactions
that emit light at specific wavelengths
and is thus not a blackbody.
* In " What Is an Aurora? " (S&T: Oct. 2023,
p. 74), we wrote that Mercury is the only
planet without aurorae. A day after we went
to press, a new research paper brought to
our attention that this is not a straightforward
matter. Particles accelerated within
Mercury's magnetosphere do indeed travel
down field lines and interact with the planet
in a way that reflects the magnetosphere's
structure. However, the particles interact
with the surface, not an atmosphere, creating
X-ray fluorescence instead of exciting
or ionizing atoms. Thus, while different,
the phenomenon is closely analogous to
terrestrial aurorae and can be called an
" aurora " for simplicity's sake.
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75, 50 & 25 YEARS AGO by Roger W. Sinnott
1948
º December 1948
Postwar Normalcy " The International
Astronomical Union, after an
interruption of 10 years, again had
a full session, in Zurich, Switzerland,
with nearly 40 international
commissions in action. New commissions
on microwave research,
close binaries, and astronomical
1973
history were set up.
" The bureau on variation of
1998
latitude made an excellent report
on the wandering of the earth's
poles. In the operation of its five
collaborating observatories, in
America, Italy, Russia, and Japan,
the bureau is a sort of United
Nations of geodesy. Dr. Bernard
Lyot, of the Pic du Midi Observatory
in France, reported on his
continuing magic touch in coronagraphy;
and the Moscow astronomers
revived the war-interrupted
Prager-Schneller handbook of
variable stars. "
Harlow Shapley was listing
astronomical highlights of 1948.
º December 1973
Moon Mystery " [A] white patch
was noted in 1823 but was
misinterpreted as the floor of a
crater six to 11 kilometers across.
In 1866 the astronomer Julius
Schmidt announced that the crater
had vanished, being replaced by a
white spot surrounding a craterlet
only about 500 meters across.
Reports of still other apparent
changes followed, and Linné
became one of the most famous
'problem' craters on the moon. . . .
" Apollo 15 photographs, which
reveal Linné as an extremely fresh
but otherwise quite ordinary impact
crater, [ended the controversy].
There is no evidence that this crater
has ever changed substantially
in shape. Totally absent is the rim
asymmetry or concentricity which
would be expected if, by coincidence,
a second impact had been
scored directly on the alleged larger
crater observed before 1866. . . .
" Evidently, optical effects were
responsible for the enigmatic
changes reported in Linné, an apt
testament to the perils of interpreting
visual lunar observations . . . "
R. Pike (U.S. Geological Survey)
adds that Linné is 2.45 km across.
º December 1998
Jovian Rings " Since its discovery
by Voyager 1 in 1979, the
ring system of Jupiter has been
a puzzle. Virtually unobservable
from Earth, the diaphanous disk is
dominated by smoke-size motes
spaced 30 meters apart on average.
. . . Particles this small are
at the mercy of forces that drag
them into Jupiter's atmosphere
or out of the ring plane. Thus they
must be replenished constantly -
but from where?
" Astronomers now know: the
dust is being blasted off the surfaces
of the planet's four innermost
moons. Cornell scientists
Joseph A. Burns, Maureen E. Bell,
and [Joseph] Veverka say the ring
particles are generated in profusion
when micrometeorites strike
the satellites' surfaces at velocities
near 30 kilometers per second. "
sk yand tele scope .o r g * DECEMBER 2023
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