The Lost Moon

I was leafing through the book "The Computer" by Mark Frauenfelder. In there, I
saw an advertisement by UNIVAC that noted that their computer was the one
powerful enough to be entrusted with the job of finding a lost moon of the planet
Jupiter!

Well, I knew that some asteroids had been lost and then recovered when a
re-discovery and orbit computations led to it being determined that the new
asteroid was the same as the old one. But this was the first time I heard of this
happening with a planetary satellite.

I Googled the story, and I did manage to find it.

The story may have been less dramatic than the disappearance of some asteroids,
but saying the moon was "lost" until the UNIVAC was put to work wasn't that
inaccurate either.

An article published in one of Univac's own magazines, Systems Magazine, was
reprinted in Computers and Automation, and the issue involved is available on Al
Kossow's Bitsavers site; it's the November 1955 issue. (Also available from the Internet Archive.)

The moon in question was Jupiter VIII, now named Pasiphaë.

This moon has an orbit fairly distant from Jupiter, and thus the Sun's gravity is important enough to make its orbit very much an example of a lunar-type orbit, a case of the three-body problem that is not well-approximated by a closed-form solution.

So back in 1938, using such automated assistance as was then available, one Herb Grosch - later famous as a columnist for Computerworld, and as a relatively nonconformist employee of IBM - in his 1942 Ph.D. thesis performed integrations of the orbit of Pasiphaë which ran until 1941.

Herb Grosch is perhaps best known for "Grosch's Law": that the power of a
computer is proportional to the square of its price. That made sense back then
when a computer had to be very big to use various techniques that made
computers more efficient - longer registers, hardware floating-point, pipelines
- of course, today, these techniques are seen even in single-chip
microprocessors.

Paul Herget, working at the observatory of the University of Cincinnati, was therefore involved with the calculation of asteroid positions for the IAU.. Dr. S. B. Nicholson, the discoverer of several of Jupiter's moons, sought to photograph Jupiter VIII, and wanted its current position.

And so Dr. Herget took on extending Herb Grosch's integrations, using time (and
programming assistance) offered by Remington Rand on their Univac computer, to
1980, as a pilot project to test the feasibility of using computers for
asteroid ephemerides. It was a success; the calculated positions were "accurate
to one minute of arc".

In my Googling, I found other interesting information as well.

Wikipedia had preserved the older, unofficial, names for several of Jupiter's satellites that people had used occasionally from 1955 to 1975.

While the names of the Galilean satellites were proposed shortly after Galileo
discovered them, it wasn't until much later that those names were routinely
used; for a long time, just calling those moons Jupiter I through IV was more
common.

Camille Flammarion was responsible for the unofficial name Amalthea for Jupiter
V; that one was ultimately adopted.

And when Charles Kowal discovered Jupiter XIII, he proposed the name Leda to
the IAU, and that became the official name; and since then, the naming history
of Jupiter's moons has been smooth.

But Jupiter VI through XII were originally named Hestia, Hera, Poseidon, Hades,
Demeter, Pan, and Adrastea, in order.

And as these names were felt perhaps "too grandiose", their official names
instead are now Himalia, Elara, Pasiphaë, Sinope, Lysithea, Carme, and Ananke.

So even before Pluto, there was cause to view the IAU as a party-pooper!

John Savard

Further searching led me to something on Google Books from which I found that it
was Dr. Brian G. Marsden who proposed the unofficial names for the moons of
Jupiter which were used by some for a time.

John Savard

On Fri, 8 Apr 2016 10:15:30 -0700 (PDT), Quadibloc
wrote:
Further searching led me to something on Google Books from which I
found that it
was Dr. Brian G. Marsden who proposed the unofficial names for the
moons of
Jupiter which were used by some for a time.

I first saw these namns for Jupiters outer moons in the books "The
Planets" by Patrick Moore in the early 1960's. That books sparked my
own interest in astronomy.

On Friday, April 8, 2016 at 7:37:07 AM UTC-6, Quadibloc wrote:

The moon in question was Jupiter VIII, now named Pasiphaë.

Some more Googling that I did led me to some more interesting information.

In fact, in my previous explorations, I had found that another of Jupiter's
moons was discovered in 1975, and then found again in 2000; but I didn't think
of it as a "lost moon" at the time, although it certainly was.

This satellite of Jupiter was S/1975 J1, temporarily known on its rediscovery
as S/2000 J1, and thus now established as Jupiter XVIII, or Themisto.

Dr. Scott B. Sheppard was is rediscoverer.

He also rediscovered S/2000 J11 after it got lost!

So there are three moons of Jupiter that could have been described as a lost
moon of Jupiter: Pasiphaë from 1941 to 1955, Themisto from 1975 to 2000, and
S/2000 J11 from 2000 to 2011.

And so Jupiter Jack, who has a radio show "Lost Moon Radio" on... oh, wait,
"Lost Moon Radio" is the name of a comedy ensemble. Based in Los Angeles. A
Google result I saw had me thinking it was a real-life radio show on a station
with the call letters KBBK.

The ensemble was founded in 2009, and during that time, S/2000 J11 really was a
lost moon of Jupiter.

John Savard