THE SOUTHWORTH PLANETARIUM
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43.6667° N    70.2667° W  Altitude:  10 feet below sea level Founded
January 1970
2021-2022: LXXXIII
"All you need is love. But a little chocolate now and then doesn't hurt."
-Charles Schulz.


THE DAILY ASTRONOMER Monday, February 14, 2022
Is Pluto About to Become a Planet Again?

[image: Poor-Pluto_art.png]

*Perhaps a Pointless Preface*
We'll preface today's article by acknowledging that some people will insist
that the article title is about three ballfields off base. They'll assert
that Pluto has always been and will always continue to be a planet despite
the lofty pronouncements of the International Astronomical Union. The
International Astronomical Union, or IAU to its friends, is , these Pluto
defenders assert, that global cabal of sinister intelligences that is
vainly attempting to exert autonomous control over all of physical reality
with its name-calling efforts. Others, of course, would argue that the IAU,
founded only in 1919, has hardly been invested with such divine powers.
Instead, it is akin to an innocuous accounting agency assigned with the
daunting and tedious task of sorting p's from q's in a Universe that is
expanding exponentially in our collective consciousness. Besides, one
should become too toffee-nosed about names. You could confer "golf ball"
status on Mercury, but good luck taking a nine-iron to it. Remember also
that Shakespearean tenet about the Rose. Refer to it as "donkey's
hindquarters" and wouldn't it smell as sweet? (Perhaps nobody would dare to
find out.) However, the Pluto defenders retort -and I promise this is
almost over- Pluto was designated a planet as soon as it was discovered in
1930 and there was no compelling reason to strip it of this coveted status.
Au contraire, the IAU defenders it was -and still is- smaller than the
planets. With a diameter of 2,360 km, it is even significantly smaller than
Mercury, whose diameter is 4,879.4 km. It is also inclined at a 17 degree
angle to the ecliptic, a far steeper inclination than the other planets. It
also doesn't fit neatly into the solar system arrangement of four rocky
bodies in front, four gas giant planets in the back, and, besides, it is
meandering through a debris field of cometary nuclei and wasn't even able
to incorporate any of this deep frozen flotsam into itself. Then again,
unlike Uranus and Neptune, which were discovered by a naturalized Brit, a
born Brit and a Frenchman,* Pluto was found by an American!** To add
stinging insult to grievous injury, Pluto's demotion was decided in a
European country!

So it goes.

*A Heaping Teaspoon of History*
Clyde Tombaugh (see second footnote) discovered Pluto in 1930 after an
exhaustive year-long search with a blink comparitor. This device enables an
observer to examine photos of the same swath of sky taken a few weeks
apart. Because planets move relative to the starfield, any planet within a
given starfield would appear to "jump" slightly from one frame to the next.
Even though Pluto is so distant that such shifts are slight even over such
a time frame, its position alteration was sufficient so as to produce a
noticeable jump. Tombaugh embarked on this search while working at the
Lowell Observatory, founded by that wealthy astronomical enthusiast
Percival Lowell (1855-1916), who originally built his namesake observatory
in 1894 to observe Martians. (We'll reserve that tale for another day.)
Unaccountable perturbations in Neptune's orbit*** prompted a global search
for a planet beyond it, hence the search that led to Pluto's discovery.
Although it was designated a planet soon after its discovery, Pluto was
soon found to have been too small to have been responsible for the
unaccountable perturbations. All the same, it retained its planetary status
until 2006, when, toward the end of the IAU's triennial General Assembly
meeting in Prague, a group of 424 astronomers voted to alter the definition
of planet and, consequently, demote Pluto. To be classified as a planet, a
body has to revolve around the Sun, be rounded and also to have cleared its
debris field. On this last requirement, Pluto was said to have failed. (As
Pluto defenders point out, most of the other planets fail, as well,
including Jupiter with its swarm of Trojan asteroids.) A lot of hearts were
shattered that August of 2006, including mine. As CalTech researcher Mike
Brown said after the vote, "Pluto is dead."

Well.

Ironically, while that small astronomical contingent was debating Pluto's
fate in Prague, the New Horizons craft was already en route to what was
then called the ninth planet. This ultra-super sonic craft was launched in
2005 and flew by Pluto in 2015. During this rapid reconnaissance mission,
the New Horizons probe discovered evidence of geological activity on Pluto,
a wholly unexpected finding. This discovery has led many planetary
scientists, most of whom were chagrined at Pluto's demotion, to declare
that its planet designation should be reinstated. They cite a 16th century
definition of a planet as any body that is "geologically active." By that
definition, Pluto, the asteroid Ceres, and many moons such as Titan,
Enceladus and Io would earn the coveted planetary status.
As University of Central Florida planetary physicist Philip Metzger boldly
said, "We think there's probably 150 planets in our solar system!" Metzger
went on to say that the IAU, perhaps worried about having to assign planet
designations on many of the bodies found beyond Pluto, set the number in
snow-cold iron as eight.

Metzger explained that most planetary scientists now ignore the IAU
definition because, by describing planets as special and rare, the
organization is behaving "astrologically." Hot damn, ladies and gentlemen,
if you want to watch astronomers turn a bright shade of vermillion, snort
flame and then pound their pocket protectors into broadswords, just accuse
them of behaving astrologically.

Of course, he has a point. Imagine how much our perceptions of the solar
system would be enhanced if we described it as harboring 150 planets
instead of just eight. Suddenly, our little niche around Sol would seem all
the more dynamic, as dynamic as the Universe, itself. 150 planets! (Can you
even begin to imagine the mnemonics?)

The IAU General Assembly is convening its next meeting this August in
Korea. Will Pluto's planetary status be then reinstated? Will the planet
number then rise from a paltry eight to a plethora of 150? Oh, but, of
course!


*German-British astronomer William Herschel (1738-1822) inadvertently
discovered Uranus in 1781. British astronomer John Couch Adams (1819-1892)
and French astronomer Urbain Leverrier (1811-1877) independently discovered
Neptune

**American astronomer Clyde Tombaugh (1906-1997) discovered Pluto in 1930.
Now, heavens above, as far as the nationalist sentiment is concerned, one
could sift through all the amber waves and not find anyone as
quintessentially American as Clyde Tombaugh. Originally a farmer, he was
driven westward by the Dust Bowl disaster to pursue his passion for
astronomy and ended up as a young staffer with the Lowell Observatory. He
literally leapt out of the "Grapes of Wrath" and landed broadsides onto a
Rockwellian cover of the Saturday Evening Post. Although in later life he
certainly could have given himself airs of Olympian aloofness, he was, by
all accounts, ingratiatingly humble and remained unassumingly Earthbound
throughout.

***Perturbations are "nudges" induced on planets by other planets and
massive bodies. We recall that all massive objects exert a gravitational
influence over every other massive object, the extent of which depends
directly on the object's mass and inversely on the square of its separation
distance. Astronomers had taken into account perturbations induced by the
solar system objects then known. However, they had also observed
perturbations that none of the known bodies could have induced, hence the
search for the ninth planet.

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