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A Moon
By Any Other Name |
Did
you ever wonder how newly discovered moons and new features on planets are
named?
When Galileo first aimed a
telescope at the Moon in 1610 he saw mountains that looked very much like
Earthly mountains. Thus we have a
the lunar
Craters, however, and some
other smaller features are named, on our Moon, after philosophers and
scientists. For example, a most obvious crater on the side of the Moon that
always faces us (the moon is tidally locked to rotate at its orbital rate) is
the huge rayed crater Copernicus. It is so large that if you were standing on
it you would not know that you were in a crater (the horizon on the moon is
only two miles away and Copernicus is almost 300 miles in diameter). There is
the crater named Tycho near the south lunar pole.
It's rays lead to the impact crater Kepler - since Kepler, the first modern astronomer and the first to
discover how the planets moved, used Tycho Brahe's observations to derive his three planetary laws of
motion (so the rays sort of indicate Tycho sharing
his data with Kepler).
Aristarchus is another small but obvious
crater; the interior is made of the brightest material on the moon. Like Aristarchus himself (who lived in the 3rd Century B.C. and
was the first to point out that the Sun was the center of the solar system) the
crater, while having little impact on the surrounding Moon, shines more
brightly than any other spot on the Moon. Socrates, Plato, Archimedes, Tsilkovsky, Pasteur, Kuiper are
all crater names on the Moon along with other great ancient and modern
philosophers and scientists. On the back side of the Moon, because
But what
about feature on, for example, the planet Mercury? These are generally named after
famous authors and composers. (By the way, the naming of the celestial bodies
is the task of the naming committee of the International Astronomical Union;
star names have been recently sold arbitrarily along with a picture of the
star, but this questionable practice has never been recognized by the IAU and
such names are never used by the professional astronomical community). Thus we
have craters on Mercury named Tolstoy, we have Bach
crater, and the
As other examples, on Mars
valley networks are generally named after rivers or other languages' names for
Mars or planets—many ancient languages are used. For example there is
Since Jupiter has no
surface,(none of the gas giant planets do) there are
no lasting impact craters to be found there, but the innermost large moon of
Jupiter, named Io, is known to be the most volcanically active moon in the
solar system with up to a dozen simultaneous volcanoes being seen spouting
material hundreds of kilometers into space when a spacecraft last looked.
Such features on this moon
are thus named after fire gods, such as Pele (the
Hawaiian goddess of fire whose work is clearly evident on the big
Skipping around, we find
that the largest rings of Saturn are named A, B, and C for asymmetric, bright,
and crepe rings (clearly planetary scientists were not expecting the thousands
of rings found there by the Voyager spacecraft). However, the dubious pleasure
of having gaps (clearings in the rings) named after one goes to Cassini (the Cassini division is
a gap in between the A and B ring), Maxwell (he also figured out the nature of
the rings), and Keeler—the first director of Lick observatory in San Jose,
California, who observationally proved that the inner rings indeed rotated
faster than the outer rings (i.e., the rings were really particles in orbit
around Saturn).
As other examples, many
features on Saturn's moon Mimas are named after
characters in King Arthur's court. We have Galahad, Lancelot
, Kay, and Guenevere craters there. The features on the
moon Enceladus are largely named after characters in
the Arabian Nights. Thus we have Aladdin, Ali Baba, and Sinbad, as well as Shaharazad crater. Until the Voyager spacecraft's encounter
with the Uranian system, moons there were named after
Shakespearean fairies, but are now named after Shakespearean characters in
general. It was in this regard that I had occasion to learn firsthand how moons
are named.
I was an associate member
of the Voyager imaging team during the 1986 first encounter with the Uranian planetary system. Before the encounter five Uranian moons were known, and 8 rings had been discovered
by airborne astronomy. (The Kuiper airborne
observatory had flown in the path of Uranus' motion watching a star pass behind
the planet Uranus with an idea toward understanding, for example, the depth of
its atmosphere, but had found the star flashing on and off on either side of
the planet as well which was due to the ring material on either side).
A colleague of mine, Bruno Sicardy (of Observatoire de
Paris) and I noticed that on a particular long exposure of the rings of Uranus
taken by the Voyager spacecraft that one of the stars did not seem to be moving
in the same direction as the others. "That's a new moon" we said, but
our colleagues doubted this, indicating that it was probably one of the known
moons or that perhaps we had mistaken its motion. With the help of navigation
calculations done by Steve Synott at Jet Propulsion
Laboratory (one of the navigation team), we obtained a prediction as to when
the moon, if real, would be seen in any additional pictures coming in from the
Voyager imaging system. If real, such images would appear again going across
the field of view in the pictures being transmitted the very next morning. I
got caught up in traffic early the next day, but when I got in folks on the
Voyager Imaging Team greeted me with, "Congratulations! You’ve discovered
a new moon!" Yippee! Bruno and I had discovered whole new tiny little
world!
We called my brother, who
was well acquainted with Shakespearean literature, and the decision for a
suggested name rested between "Mab" and
"Peaseblossom" both fairies from
Shakespeare's "A Midsummer Nights Dream". We suggested the name
"Peaseblossom" then, which was well
received by the scientists on the Voyager imaging team. Ah, but a controversy
arose about the names of the new Uranian moons when a
congressman, a few weeks later, suggested that the newly discovered moons of
Uranus be named after deceased astronauts —a suggestion that soon drew a reply
from the then Soviet Union pointing out that naming them after deceased
cosmonauts was equally valid. This, then, actually started a bit of an
international scuffle! Thus no name was assigned to our little "Peaseblossom" for several years.
Finally the name
"Bianca", a Shakespearean character from Taming of the Shrew, was
quietly chosen by the IAU committee on naming moons and in the Smithsonian
Institution in Washington D.C. you will see that the Voyager spacecraft is
(really rightly so) credited with discovery of a little Uranian
moon named "Bianca" about 20 kilometers across. Ah well, I still like
the name "Peaseblossom" and nothing, to my
knowledge, is yet named "Peaseblossom" in
the heavens. However, Shakespeare is still a daily part of my life, as I have
named the computer on my desk "Peaseblossom."
It is there to remind me that Bruno and I were the first ever to know of a
wholly new little world. And when I remember the thrill of that discovery, by
any other name, it still smells as sweet.
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