Sky & Telescope - June 2019 - 9

1907 paper she writes, "It is worthy of
notice that . . . the brighter variables
have the longer periods." In the library
at the Harvard-Smithsonian Center for
Astrophysics, that 1907 paper is bound
into a volume dated 1906-1908, making
it impossible to know the exact year
the paper appeared and explaining why
the year 1908 often appears instead.
Imagine, then, my joy when I saw the
same paper here in the Berkeley library,
with each individual paper stamped
with the date on which the library had
received it!
Ken Croswell
Berkeley, California

Camille Carlisle replies: I cited

1912 because Leavitt's 1907 paper
seemed less deﬁnitive to me. In the 1912
work she writes that "In [the previous
work], attention was called to the fact
that the brighter variables have the longer
periods, but at that time it was felt that
the number was too small to warrant the

drawing of general conclusions." Thus, I
considered 1912 to be the year that it all
came together. But she certainly saw a
trend earlier, so using the earlier date for
the discovery makes sense.

Kept in the Dark
I had an optical mishap similar to Pat
Plunkett's (S&T: Jan. 2019, p. 84).
At a public star party a few years ago,
I was trying to ﬁnd M27, the Dumbbell Nebula in Vulpecula, using my C8.
It wasn't a Go To, but I had nailed the
object many times before by star-hopping. But for the life of me I couldn't
ﬁnd it that night. When the crowd left,
I tried again and again just out of stubbornness. No luck. I eventually hurt my
back trying to ﬁnd the object, which
was nearly at the zenith.
The next day, as I put away my equipment, I noticed the eyepiece had an

1969

1994

Bill Dellinges
Apache Junction, Arizona

FOR THE RECORD

* John Goodricke identified Delta Cephei's
periodic pulsations in 1784, not 1794 as
printed (S&T: Mar. 2019, p. 16). Incidentally,
although Delta Cep is often reported as
the first Cepheid discovered, Eta Aquilae
technically beat it by a few weeks (S&T:
Oct. 1997, p. 90).

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75, 50 & 25 YEARS AGO by Roger W. Sinnott
1944

orange ﬁlter still screwed into it. I use
that ﬁlter for Saturn. At the star party,
I had been on Saturn before deciding to
move on to M27, and I forgot to remove
the orange ﬁlter. While I know better
than to use a planetary ﬁlter on a nebula, I had no idea an orange ﬁlter would
make the thing completely disappear. I
could have spent all night looking for
that nebula and never found it!

º June 1944
Cometary Aurora? "[Sylvain]
Arend, at Uccle, Belgium, noticed
a nebulous object of 13th magnitude with a nucleus, close to
Comet Whipple (1942g) on March
29, 1943. . . . [Not long after,]
Dr. Brunner-Hagger, at Zurich,
Switzerland, [recalled] that a fine
aurora had been seen on March
27.8. Terrestrial aurorae are caused
by corpuscular radiation from the
sun. Suppose the diffuse object
in the comet's tail had the same
origin? From the time elapsed . . .
he deduced that the solar corpuscles travel at the rate of about one
astronomical unit in 30 hours."
A clever suggestion! In fact,
coronal mass ejections from the
Sun put a kink in the tail of Comet
Ikeya-Zhang in 2002 and blew off
most of Comet Encke's tail in 2007.
º June 1969
Phantom Planets "Distant only 5.9
light-years from us, Barnard's star

is traveling across the sky at the
enormous rate of one degree in 350
years. This proper motion shows a
very slight waviness, from which in
1963 Peter van de Kamp of Sproul
Observatory deduced the presence
of an unseen companion. . . .
"Now Dr. van de Kamp points
out an alternative interpretation of
the observations. The measured
deviations of Barnard's star may
result from perturbations by two
unseen companions, revolving in
approximately coplanar circular
orbits with periods of 26 and 12
years. . . . The deduced masses are
1.1 and 0.8 that of Jupiter, respectively. These objects may therefore
be thought of as planets."
Probably van de Kamp was
misled by astrometric errors. As far
as we know today, no exoplanets
circle Barnard's Star, but about
4,000 of them belong to other
host stars. Most were identiﬁed by
subtle variations in the star's radial
velocity, or else by weak dips in its
light during transits by the planet.

º June 1994
Ida's Moon "Two instruments on
the Galileo spacecraft have found
a small satellite within 100 kilometers of the asteroid 243 Ida. A mere
1½ km across, the tiny moonlet
appears in images taken . . . during
a flyby of Ida last August 28th. . . .
"Most probably the two objects
ended in the same vicinity after
the collision long ago that created
the Koronis family of asteroids.
. . . In that case the moon could
have been captured into a stable
orbit. . . . Project scientists hope
to resolve such questions about
Ida and its companion once the
remaining Galileo images and
spectra are in hand."
Earlier there had been a few
reports of two dimmings as an
asteroid occulted a star, suggesting a satellite. But Ida's moon, later
to be named Dactyl, was the ﬁrst
proven case (not counting Pluto's
Charon, spotted in 1978 when Pluto
was still considered a major planet).
Almost 400 asteroidal moons are
now known to exist.
sk yandtele scope.com * J U N E 2 019

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Sky & Telescope - June 2019

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