Sky & Telescope - December 2022 - 7

for you " certificates about 30 years ago
but never knew where to look for it.
I compared the chart he'd been
given with my star charts and planetarium
program, and even plugged the
supposed coordinates into my Go To
scope. Nothing! At least, nothing was
visible from within city limits.
If there was a star there, it must
have been very dim. I'm pretty sure
he got taken. I didn't want him to be
disappointed and considered pointing
out something fairly bright and declare
that to be " Dave's Star, " but I just
couldn't do it.
Ringwald's letter reminded me
of that incident, and his thought
of pointing to Venus was hilarious.
Thanks for the laugh!
Michael Coon
Tempe, Arizona
Phobos
The short quote from a review of A. T.
Sinclair's work in Roger W. Sinnott's
75, 50 & 25 Years Ago ( " Wandering
Phobos, " S&T: Aug. 2022, p. 7) left the
reader with the impression that Mars's
satellite Phobos is not undergoing a
secular acceleration in longitude. The
opposite is true.
Much work has been done on the
motion of Phobos since Sinclair's 1972
study. Of note is Sinclair's 1989 study
(https://is.gd/Sinclair1989), in which
he informs us that Trevor Morley
discovered an error in the database
of observations used by Sinclair and
George Wilkins before him. With
the error corrected, Sinclair finds a
significant value of 0.00124°/y2 for
the secular acceleration of Phobos, in
close agreement with current values,
and about one third smaller than the
value first reported by Bevan Sharpless
of the Naval Observatory in 1945
(https://is.gd/Sharpless1945).
Considering that Sinclair fit an
updated theory to the motion of Phobos,
included additional modern observations
in his solution, and used more
sophisticated computational methods,
Sharpless' value should be considered a
valid result despite the sizable difference
with modern values.
Robert Jacobson wrote a good
review of the work on the Martian satellites
in his 2010 article (https://is.gd/
Jacobson2010).
[Re Sinnott's comment], had anyone
taken Shklovskii's suggestion seriously,
it would not have been Sinclair's 1972
paper that convinced them that Phobos
was not artificial. Rather, the photographs
of the two Moons taken by
Mariner 9 that same year would have.
Dan Pascu and Steven J. Dick
U.S. Naval Observatory (retired)
Washington, DC
SUBMISSIONS: Write to Sky & Telescope, 1374 Massachusetts Ave., 4th Floor, Cambridge, MA 02138, 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
1947
1972
º December 1947
Messier's Mistake " During the
course of [other recent] work,
Dr. [Helen Sawyer] Hogg found
a letter from Pierre Méchain in
Paris to M. Bernouilli, published
in Bode's Jahrbuch for 1786. This
letter clears up the identification
of No. 102 in [Charles Messier's
catalogue]. Although Messier
confirmed the discovery of most of
these, Nos. 101, 102, and 103 are
listed as seen by Méchain only.
" In the letter now brought to
1997
light, Méchain corrected the listing
by stating that No. 102 is 'one and
the same with No. 101,' and that
Messier made a mistake in reading
its position from the star chart.
Some astronomers had tentatively
identified M102 as . . . NGC 5866. "
Lying just north of the Big Dipper's
handle, M101 is the magnificent
Pinwheel Galaxy. Some 9° east
of it is NGC 5866, a much fainter
galaxy. Some writers still wrongly
equate M102 with NGC 5866.
º December 1972
Space Telescope " The 1980's
should see the establishment of the
first major observatory in space, as
a result of the Large Space Telescope
(LST) program of the National
Aeronautics and Space Administration.
This observatory will contain
a long-lifetime reflecting telescope
of about 120 inches clear aperture,
and will be repairable and refurbishable
while in earth orbit . . .
" The instruments [will include] a
television camera capable of resolving
the diffraction-limited images,
and low- and high-dispersion
spectrographs. . . . Although the
first launch date, in 1980, seems
remote, our long lead time indicates
the many developments that must
be made in building a cost-effective
new system. "
After this forward look by C.
R. O'Dell, the launch was much
delayed, the aperture shrank, and
the cost soared. But that meant the
renamed Hubble Space Telescope
could use a modern CCD detector
instead of a " television camera. "
º December 1997
Asteroid Moons " Three asteroids
have been photographed closeup
by spacecraft: [951 Gaspra in
1991, 243 Ida in 1993, and 253
Mathilde last June]. The most surprising
discovery in these encounters
was the little moon that orbits
Ida. One asteroid satellite seen
in just three good looks - those
numbers led some solar-system
specialists to suspect that asteroid
satellites are common. Now it
looks as if they're right. . . .
" Earth itself bears graphic
evidence that asteroids sometimes
come in pairs. Of the Earth's 28
largest impact craters, three are
doublets formed by the nearly
simultaneous impacts of two
bodies. And planetary scientist
William Bottke (Cornell University)
sees comparable rates of doubleimpact
features on Venus, Mars,
and the Moon. "
Currently, William Robert
Johnston's online archive lists
469 asteroids known or strongly
suspected to have satellites.
sk yand tele scope .o r g * DECEMBER 2022
7

https://www.is.gd/Sinclair1989 https://www.is.gd/Jacobson2010 https://www.is.gd/Jacobson2010 https://is.gd/Sharpless1945 https://skyandtelescope.org/

Sky & Telescope - December 2022

Table of Contents for the Digital Edition of Sky & Telescope - December 2022