Sky and Telescope - June 2018 - 7
I'd like to point out that the extremely
elongated shape of the recently discovered interstellar visitor 1I/'Oumuamua
(S&T: Feb. 2018, p.10) is not all that
unprecedented. In 1999, the spacecraft
Deep Space 1 ﬂew by the asteroid Braille
and found it to consist of a long string
of small rounded bodies. Several images
of other small solar system bodies have
shown them to be made up of two or
more "lobes" connected together. The
media reports of 'Oumuamua as being
so unusual as to possibly be artiﬁcial
are, indeed, "hyperbolic."
Kelly Beatty replies: Yes, 9969
Braille is deﬁnitely elongated, and it
conceivably might be a chain of connected
fragments. But this little asteroid spins very
slowly, every 226 hours, whereas the rotation period of 'Oumuamua is 8 hours. Such
a highly elongated object rotating that fast
can't hold together unless it's solidly bound
as a whole - what geologists term "monolithic" - rather than a collection of pieces.
A Family Affair
Surely Sky & Telescope is a familyfriendly publication. Nevertheless, you
might have added new meaning to the
term with the January 2018 issue.
I refer to your plaudits for a telescope
based on a design by John Dobson (p.
30); the citing of Harold F. Weaver as
co-discoverer of Berkeley open clusters
(p. 55); and mention of the Trumpler
2 cluster (p. 62), named after Lick
Observatory's Robert J. Trumpler. It's a
veriﬁable - albeit obscure - fact that
these three people were matrimonially
related, a consequence of choices made
by two of Trumpler's daughters: Cecile,
the eldest, married Weaver; Elizabeth
Julie, the youngest, married R. Lowry
San Leandro, California
FOR THE RECORD
* Colorful sunrises and sunsets on Earth
(S&T: Jan. 2018, p. 49) are caused by
Rayleigh scattering of sunlight's blue wavelengths by air molecules.
* The 24°×24° field of view of the TESS
cameras (S&T: Mar. 2018, p. 24) is equivalent to the area covered by nearly 2,100 full
* The images of Venus (S&T: Mar. 2018, p.
53, bottom caption) were obtained using a
filter that transmitted wavelengths longer
than 610 nm.
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75, 50 & 25 YEARS AGO by Roger W. Sinnott
Dobson, one of John's brothers.
If S&T's editors had wished to
highlight this familial conjunction, I
suppose you could have urged readers to
view the Berkeley and Trumpler clusters
with a Dobsonian reﬂector.
º June 1943
Spiral Puzzle "It has been known
for a long time that the spiral
nebulae are in rotation. The radial
velocities in spirals sufficiently
inclined to the line of sight tell us
that one edge is receding relative
to the other, which is approaching us. Astronomers have been
puzzled, however, as to the actual
direction of rotation: are the spiral
arms trailing behind or going on
ahead? This question is important
in theories of the origin and future
of these galaxies. . . .
"Now Dr. Edwin Hubble, one of
the foremost authorities on extragalactic nebulae, finds sufficient
evidence in the famous Mt. Wilson
collection of photographs to state
. . . that probably all spiral arms are
The debate went on for
decades, but today we know Hubble was mostly correct. A muchstudied exception is NGC 4622 in
Centaurus. Starting in 2002, work
of a team led by Ronald J. Buta
(University of Alabama) has shown
that the outer tips of its arms actually do lead.
º June 1968
Death by Supernova "Although in
our galaxy Type II supernovae may
occur as often as twice a century
. . . most must be at such vast distances from us that their cosmicray flux would arrive highly diluted.
Suppose, however, that . . . such
a supernova explosion occurred
within a few hundred light-years of
the sun. . . .
"The possibilities have been
explored by biochemist K. D.
Terry of the University of Kansas
and space scientist W. H. Tucker
of Rice University. . . . The paleontological record clearly shows
periodic mass extinction of large
groups of animals (not plants). . . .
It is calculated that since pre-Cambrian times 600 million years ago,
perhaps four nearby supernovae
caused radiation of 1,000 roentgens at the earth. . . ."
Notwithstanding today's wide
acceptance that the Chicxulub
impact killed the dinosaurs, nearby
supernovae remain another viable
threat to life on Earth.
º June 1993
Evil Genius "Astronomers who
enjoy Sherlock Holmes mysteries
recently learned that they might
have more in common with Prof.
James Moriarty, master criminal,
than with their hero - at least
in the imagination of English
storywriter Arthur Conan Doyle.
Astronomer Bradley Schaefer has
uncovered evidence that Moriarty
is actually a thinly veiled fiction
based on . . . American astronomer
. . . Simon Newcomb. . . .
"Schaefer has also uncovered
long excerpts copied from the
detective stories in Mrs. Newcomb's hand. . . . She must have
been pleased by the character
who, in Doyle's words, [had] 'a
brain of the first order' - in short,
the only man smart enough to
outwit Sherlock Holmes."
sk yandtelescope.com * J U N E 2 018