The Defenestration of Pluto
The Rise and Fall of the 9th Planet
Dr. Shadow JQ Robinson
Sept 19 2009
Announcing your 9th Planet
Feb 18th 1930
Clyde W. Tombaugh working
at the Lowell Observatory in
Found by comparing
photographs taken of the
same region of the sky
My very educated mother just
served us nine pizzas
Looks easy eh?
Pluto’s Day of Doom
After years of brewing
trouble, in 2005 (Jan
5th) an object is
the sun larger than
Originally called Xena
by its discoverer, now
known as Eris
Proof that Xena is larger than Pluto
How did it come to this?
1543 Copernicus published the definitive
statement of the heliocentric system in De
Revolutionibus in 1543
There are 6 planets, Mercury, Venus,
Earth, Mars, Jupiter and Saturn
(My Very Educated Mother Joyously
1781- 7th Planet
Sir Frederick William
radiation, first evidence of
Had many names until
Uranus became standard
in mid 1820’s
(My Very Educated
Mother Just Sang U2)
1801 – 8th planet
Ceres is discovered between Mars and
By 1807, 11 planets. Pallas, Juno, and
Vesta join the party, all about the same
distance away as Ceres.
(My Very Educated Mother Vicki Just
Called Paul Johnston Super Ugly)
1845 The 12th planet
Astraea, found accidentally when looking
My Very Educated Mother Vicki Anderson
Just Called Paul Johnston Super Ugly
1846-The 13th Planet!
Neptune is discovered! (Galileo had seen
it in 1612/1613 but did not know what it
The Orbit of Uranus was wobbly, did not
follow expected pattern.
Mathematicians John Couch Adams and
Urban Le Verrier calculated the orbit of a
planet that could cause the behavior (U.
Le Verrier deserves most of the credit.)
AND IT WAS THERE!
A great feat of mathematics, and a lucky
chance in the timing
Calculated orbits of Neptune were decent
for only a 10-15 year period.
So we now have
My very educated mother Vicki Anderson
Just Called Paul Johnston Some Ugly
1851 – the 23rd planet is
Hebe, Iris, Flora, Metis, Hygiea,
Parthenope, Victoria, Egeria, Irene and
All in same general area as Vesta, Juno,
Ceres, Pallas and Astrea.
My very educated mother formerly Vicki,
verily is marrying Hank. Paul as expected
is extremely jealous, certainly Paul
Herman Johnston’s some ugly nerd!
1852 – The madness stops
15 space rocks, none very big, all in the
same general area.
This region of space is now called the
asteroid belt, tens of thousands are
known, probably are millions of them.
All of them added together has 1/25th the
mass of the moon.
Maybe they should not be planets
Neptune seemed to wobble from its
Lets try to calculate where another planet
might be, like Neptune’s discovery.
Pluto was pretty close to where the
calculations said it should be.
WAY to small to cause the wobble.
Turns out there was not a wobble, just a
lot of luck!
How big is Pluto?
First estimates were based on brightness.
It was not big, somewhere between Earth
and Mars perhaps based on its brightness.
As we kept looking, the size kept getting
35 years ago the estimates had it about
the size of Mercury.
Then these pictures were taken
Pluto has a moon!
The estimates of Pluto’s size had come
from assuming that point of light was all of
It is actually light from Pluto and its moon
The moon is actually half the size of Pluto!
First semester physics allowed us to
compute mass of Pluto. (450 Plutos = 1
More Pluto Facts
We realize now that it’s brightness was
because of two things.
It has a moon, and it is shiny.
So it is much much smaller than originally
Compute the density of it to guess its
It is like a giant comet.
More moons for Pluto! (2005)
The life of Pluto
Pluto had a pretty dull life until the
discovery of Charon in 1978.
The Voyager I spacecraft could have
chosen to visit Pluto but did not from,
among other concerns, a lack of interest,
going to Neptune’s moon Triton instead.
It is bigger after all.
More life of Pluto
On February 7, 1979 Pluto was closer to
the Sun than Neptune. This would last
until February 11, 1999.
But due to the interplay of their gravity,
(i.e. Neptune telling Pluto where it is
allowed to go) Pluto never gets within 30
AU of Neptune. (1 AU = distance from
Earth to the Sun)
Pluto has company!
In 1992, the second Trans-Neptunian
Object (TNO) is discovered.
Dozens of small TNO’s found before 2000
Now there is more than a thousand known
TNO’s, Pluto has a lot of company.
The beginning of the End
In 1999, the International Astronomers Union
(IAU) started a catalog numbering the TNO’s.
There was a desire to give Pluto number 1.
When word reached the press, public outrage
prevented Pluto from being in the catalog.
2000 – discovery of Varuna. It is a TNO that is
It is about a quarter the size of Pluto.
Is it a planet?
Of course not, its just a big TNO. Anyway it’s a
lot smaller than Pluto.
Asking for trouble
2000 - Hayden
renovation in New
York with Neil
deGrasse Tyson as
Pluto is not included
as a planet.
Is a way to get death
threats from 4th
More Round TNO’s
Discoveries follow quickly as it is clear
there are millions if not billions of TNO’s
Approximately 10 round TNO’s are found
Are they to be planets?
Not as big as Pluto
2005 Mike Brown
Discoverer of many round TNOs,
When I discovered it and realized that it
was, indeed, bigger than Pluto, I
immediately called my wife and excitedly
told her "I found a planet!“
So now the IAU, the group of scientists in
charge of such things as planethood had
to make a decision. What is a planet? No
definition had ever been given.
Efforts at Definition
Many astronomy textbooks do not even have
definitions in the late 90’s early 2000’s
(2003 – Basari) If it is round, because of its own
gravity, and goes around the sun, poof it’s a
1st IAU group tries and fails to come up with a
2nd IAU group proposes a definition at the 2006
meeting. It is essentially the Basari one.
2006 IAU meeting beginnings
The announcement that the new definition will
keep Pluto is meet with happiness by the press
Neil deGrasse Tyson goes onto the Colbert
Report and lets Colbert rub it in.
Except now there are twelve planets, including
Xena, Pluto’s moon Charon, also Ceres sneaks
back onto the list.
More definition excitement
Also there are almost certainly 53 objects total
that are already known that will have to be
confirmed as being round enough.
Brown guessed eventually there would be at
All of them either TNO’s or asteroid belt objects
that will get back in after 150 years out.
In a few billion years, even our Moon could
become a planet!
Some of the new planets
Well where do these guys live?
Sedna and other oddities
Most distant thing observed in orbit around the
Orbits sun every 12,000 years (Pluto 246)
The Oort cloud and Kuiper belt are recently
estimated to have a quadrillion objects
A QUADRILLION! 1000000000000000, we have
only seen less than 100,000 and already will
have 53 planets by the new definition
While the suggested definition soothes public
fears that Pluto will lose its planethood, the
astronomers that care are mostly in uproar.
(Planets should be special, going from 9 to 53
does not feel right.)
(Planets should be dominating gravitational
presences, not just any round space rock or
Especially when all the new ones are all
essentially the same kind of object, many in
practically the same place.
Just like in 1850’s with the asteroid belt
More similarities to 1850’s
Neptune’s Gravity is for a large number of
these object’s determining their orbital
IAU meeting 2006 Prague
The August 16th Definition was immediately met with
70 percent of those present opposed the definition in one
By August 18th, a counter definition was proposed, that
would prevent planetary inflation, at the cost of Pluto
On August 22nd, open meetings made it clear that the ‘no
Pluto’ astronomers were much in the majority
On August 24th a definition was voted on that has
become the official definition of planet.
There are 8 classical planets, and the ‘losers’ are now
known as dwarf planets.
A celestial body that is (a) in orbit around the
(b) has sufficient mass for its self-gravity to
overcome rigid body forces so that it assumes
a hydrostatic equilibrium (nearly round)
(c) has cleared the neighbourhood around its
What does it mean to clear the
“Pluto vote 'hijacked' in revolt” – the
chairman of the committee to come up with the
Pluto demotion draws protest – New Mexico
State University where Tombaugh was a
Wikipedia site on Pluto was briefly locked
Online petition for a better definition – signed by
over 300 professional astronomers
Over a thousand items on cafepress expressing
‘belief’ in Pluto’s planethood or outright anger
The State of California
WHEREAS, Recent astronomical discoveries, including Pluto's oblong orbit and the
sighting of a slightly larger Kuiper Belt object, have led astronomers to question the
planetary status of Pluto; and
WHEREAS, The mean-spirited International Astronomical Union decided on August
24, 2006, to disrespect Pluto by stripping Pluto of its planetary status and
reclassifying it as a lowly dwarf planet; and
WHEREAS, Pluto was discovered in 1930 by an American, Clyde Tombaugh, at the
Lowell Observatory in Arizona, and this discovery resulted in millions of Californians
being taught that Pluto was the ninth planet in the solar system; and
WHEREAS, Pluto, named after the Roman God of the underworld and affectionately
sharing the name of California's most famous animated dog, has a special connection
to California history and culture; and
WHEREAS, Downgrading Pluto's status will cause psychological harm to some
Californians who question their place in the universe and worry about the instability of
universal constants; and
WHEREAS, The deletion of Pluto as a planet renders millions of text books, museum
displays, and children's refrigerator art projects obsolete, and represents a substantial
unfunded mandate that must be paid by dwindling Proposition 98 education funds,
thereby harming California's children and widening its budget deficits; and
WHEREAS, The deletion of Pluto as a planet is a hasty, ill-considered
scientific heresy similar to questioning the Copernican theory, drawing maps
of a round world, and proving the existence of the time and space
WHEREAS, The downgrading of Pluto reduces the number of planets
available for legislative leaders to hide redistricting legislation and other
inconvenient political reform measures; and
WHEREAS, The California Legislature, in the closing days of the 2005-06
session, has been considering few matters important to the future of
California, and the status of Pluto takes precedence and is worthy of this
body's immediate attention; now, therefore, be it
Resolved by the Assembly of the State of California, That the Assembly
hereby condemns the International Astronomical Union's decision to strip
Pluto of its planetary status for its tremendous impact on the people of
California and the state's long term fiscal health; and be it further
Resolved, That the Assembly Clerk shall send a copy of the resolution to
the International Astronomical Union and to any Californian who, believing
that his or her legislator is addressing the problems that threaten the future
of the Golden State, requests a copy of the resolution.
What does Brown do for you
I don't want to be insensitive to the Plutophiles out there,
but enough about Pluto, OK?. I've got my own mourning
When I discovered it and realized that it was, indeed,
bigger than Pluto, I immediately called my wife and
excitedly told her "I found a planet!
Right after the astronomical vote yesterday, I made the
same phone call again. I had to tell her that the 10th
planet was being buried alongside Pluto. Her voice
dropped. Really? She said. Really. My wife was already
mourning the little planet that we had gotten to know so
The astronomers did the right thing.
PLUTO STILL EXISTS
New Horizons Probe still going to Pluto,
11:47 UTC July 14 2015 (Launch Jan
2006, passed Jupiter Feb 2007, Saturn
Pluto, while no longer the largest Kuiper
Belt object, is still the closest
Scientific value of Pluto has not changed,
and is possibly more important than
anything in the solar system
(short of finding life on Mars or in the
Pluto’s scientific value
Kuiper Belt has important information in it. (The highest
priority in a National Academy of Science panel.)
Much of the non-Trans Neptunian solar system has
suffered billions of years of geology along with asteroid
and cometary collisions, losing information on the
The Kuiper Belt still has much of that information.
Things much smaller than the earth are much harder to
Some of the same properties that make Pluto not a
planet, make it more interesting and more important than
the 8 planets.
A final word
You can know the name of a bird in all the
languages of the world, but when you're
finished, you'll know absolutely nothing
whatever about the bird... So let's look at
the bird and see what it's doing -- that's
what counts. I learned very early the
difference between knowing the name of
something and knowing something.
– Richard Feynman