PLUTO - Department of Earth and Planetary Sciences

PLUTO
Auditorio di Nihilo
*
EARTH-450
Satellites of Saturn & Jupiter
SPRING 2013
Amir Salaree
* Latin for “A lecture about nothing” since we know so little about Pluto.
1
Table of Contents:
1. Abstract (At the Edge of the Known World)
2. Introduction
2.1 Etymology (Papé Satàn, Papé Satàn Aleppe)
2.1.1 How Pluto Got Its Name (A Thracian God)
2.2 Timeline (A Novella)
2.2.1 1930: Discovery (Close Encounter of the First Kind)
2.2.2. 1977–1999: Closer to the Sun than Neptune (Habkkuk and
the Angel)
2.2.3 1978: Discovery of Pluto's Moon: Charon (Barbanito's Rage)
2.2.4 1988: Pluto Has an Atmosphere (Die Zertanzten Schuhe)
2.2.5 2005: Discovery of 2 Additional Moons (Yin and Yang)
2.2.6 2006: New Horizons is Launched for Pluto (Neither Snow
Nor Rain Nor Heat Nor Gloom of Night)
2.2.7 2006: Pluto Is Excluded from the List of Planets
(Prometheus Bound)
2.2.8 2011: A New Moon Is Discovered around Pluto
(A River Flowed Out)
2.2.9 2012: Another Moon Is Discovered around Pluto (In a Cloud
of Dust and Smoke)
2
3. Known Facts about Pluto (Much Ado for Nothing)
3.1 General Attributes (Take It or Leave It)
3.2 Pluto Has Five Moons (On the Cross)
3.3 Why Is Pluto Bright? (The Dragons Were Crying)
3.4 Orbit (Close Encounter of the Second Kind)
3.5 Moon(s) (The Union Club Mysteries)
4. Kuiper Belt (The Wild Bunch)
5. New Horizons (Le Livre des Merveilles)
6. Conclusion
3
1. ABSTRACT (At the Edge of the Known World)1
Since its discovery in 1930, very little new data has been gathered about
Pluto. Most of the present data is acquired using ground-based observatories as
well as Hubble Space Telescope (HST). Most of the stuff we know about Pluto has
been provided by close analysis of these data. At the very edge of the known
solar system (and 'aptly' named) Pluto is more complicated and ambiguous than
any other object (with few exceptions) in our solar system. It's lopsided orbit and
the fact that it has an atmosphere (at ~50K !!) are jut a start. Its five known
moons along with Pluto make up a very complex system of masses which orbit
and revolve about points outside of any of them.
Ever since its exclusion from the list of planets in 2006, Pluto has offered
more wonders than anytime before. New Horizons' visit in 2015 will definitely be
a major breakthrough to our understanding of the solar system and this most
ancient and out-of-reach region of the solar system.
In this paper, the evolution of our knowledge about pluto has been
presented in a chronological order. The mythical aspect of Pluto (the fact that
until 2015 we will not know much about it and it is still in shadows) has added
such an aspect to this manuscript with hints towards enchanting corners of
human literature (as footnotes and small title additives in parentheses to avoid a
non-scientific approach or ambiguity).
1 Zeno at the Edge of the Known World is the title of a book by Joseph Kosuth.
4
2. INTRODUCTION
2.1 Etymology (Papé Satàn, Papé Satàn Aleppe)
The name Pluto (Plouton) is adapted form Greek mythology. There is a
common conflation in the Grecko-mythical characters on Pluto. The conflation is
a result of translating two identical names Plouton and Ploutos into English.
Ploutos (Fig. 1) was a god of wealth, because mineral wealth was found
underground, and because as a chthonic god, Pluto ruled the deep earth that
contained the seeds necessary for a bountiful harvest.
Ploutos, "Wealth," appears in Hesiod's (c. 750 – 650 BC) Theogony as the
child of Demeter and the demigod Iasion. In the Theogony, Hesiod praises
Plouton (Pluto)'s beauty as in “... Kerkeis with the lovely stature and cow-eyed
Plouto ... .”2. Ploutos was born as a result of an intercourse on a thrice-ploughed
field which obviously hints to fertility, wealth and blessing.
An earlier name for Pluto was Hades (Fig. 2) who was brother to Zeus and
Poseidon, and tricked by Zeus was ruling over the Dead and the world of the
undying. The name Plouton does not appear in Greek literature of the Archaic
period. In Hesiod's Theogony, the six children of Cronus and Rhea are Zeus, Hera,
Poseidon, Hades, Demeter, and Hestia. The male children divide the world into
three realms. Hades takes Persephone by force from her mother Demeter, with
the consent of Zeus.
The climax to this conflation is best seen in Ovid's3 Metamorphoses4
where Pluto is the name of the Lord of the Dead whose name means 'wealth' and
his underworld kingdom is called Hades.
The contrast between the two characters is best demonstrated by their
affair with Persephone. According to the myth, Ploutos is the loving husband to
Persephone, while Plouton (Hades) abducts and forces her into marriage.
2 Theogony, Hesiod, c 700 BC.
3 Roman poet, 43 BC – 17/18 AD.
4 First Published in 8 AD.
5
Figure 1. Plutus – Ploutos (God of Wealth)
The J. Paul Getty Museum, Malibu,
California, USA, ca350 - 340 BC
Figure 2. Pluto – Plouton (Demter and Lasion's son) – Hades.
Antikensammlungen, Munich, Germany, ca330 - 310 BC
Aristophanes portrays Pluto (Plutus) as a blind beggar in his play called
Plutus who brings fortune to an old man's house as foretold by the Delphi oracle.
The character Pluto, appears in the literature interestingly enough, later in
the 14 century Inferno by Dante Alighieri as a repulsive, small creature guarding
the gates of the underworld (Fig. 3). Canto VII in the Inferno opens by a weird line
of three words: “ Papé Satàn, Papé Satàn Aleppe ...” and is not clear in meaning.
The most widely held idea is that it is used as an evil warning or salutation 5 so
that Dante and Virgil should be aware of their crossing into the world of the
Dead.
th
5 There are different theories about the exact meaning of the phrase. But where they all condescend is that Papé has a
feeling to “father” or “chief; Satàn is an attributed name to Satan (who is at the end of inferno seen as an archangel and
evil being imprisoned in the “bottom of bottoms” and the center of the Earth) and Aleppe is an attributed word for alpha
which almost means “God” or “Supreme”.
6
Figure 3. Pluto in the Inferno, Divine Comdey, by Dante Alighieri.
Illustrated by Gustave Dore (1832 – 1883).
2.2.1 How Pluto Got Its Name6 (A Thracian God)7
Pluto is the only world named by an 11-year-old girl. In 1930, Venetia
Burney of Oxford, England, suggested to her grandfather that the new discovery
be named for the Roman god the underworld. He forwarded the name to the
Lowell Observatory and it was selected. Pluto's moons are named for other
mythological figures associated with the underworld.
As will be described later in the text, Pluto has 5 known moons. The
etymology of their names will follow in the Appendices (see Appendix III).
6 This section is quoted from the NASA factbook.
7 In Aristophanes (427 – 386 BC) famous play “The Birds” The old gods send as embassador, Hercules, Poseidon and a
Thracian god who cannot speak Greek correctly and talks in the form of gibberish.
Pluto was named among the planets of the solar system, but later on proved to be very different and unusual and
therefore was re-categorized as a dwarf-planet.
7
2.2 Timeline (A Novella)
2.2.1 1930: Discovery (Close Encounter of the First Kind8)
Search for the 9th planet in the solar system has long been the ambition of
many astronomers. Neptune has officially been claimed as the 8 th planet of our
solar system since 1781 (although it's also observable to naked eyes) 9, but
astronomers have been looking for a massive enough object (Planet X) beyond
Neptune that could justify the perturbations observed in Neptune's orbit.
In 1920s, the famous astronomer, Vesto M. Slipher who was the director
of Lowell observatory at the time, recruited a good amateur astronomer who
might be trained to take long-exposure photographs with their new 13-inch
astrograph – a telescope specially built to continue the search for a 9th planet.
Percival Lowell, the founder of the observatory thought, if he could predict the
location of a ninth planet, beyond Neptune, and then find it, it would surely
improve his status (Tombaugh, 1986). At the faintness this planet was predicted
to be, there are millions of points of light in the sky and the task is to find one
that shifts its position relative to the background stars…Such a search required
photography to “freeze” all of the light images with an hour exposure. Then one
must obtain a duplicate photographic record a few nights later. The real stars
show no change in position during such a short interval, but a trans-Neptunian
planet will show a small shift in position, and thus betray its planetary nature. An
instrument called a blink comparator can be used to flash the two photographs
on a screen in rapid alternation, to make it easier to see the point of sight that
has moved.
It was so, that Slipher recruited Clyde Tombaugh. Clyde Tombaugh then
discovered Pluto using this technique in February 18, 1930. In his own words:
8 Discovery of Pluto reminds one of UFO sighting, and especially the close encounter of the first kind, since for a while
there was no other tangible evidence of its presence than it just should be there. It did not even meet what astronomers'
expected of a ninth planet.
9 People with good eye-sight can see Uranus on clear nights, but since Uranus is a dim and slow planet (orbital period of
~84 yr), had never officially claimed as a planet, until Sir William Herschel did it on March 13, 1781.
8
“... On Feb 18th, [while the Moon was too bright for
observing], I decided [to blink] the Delta Geminorum
plates. Upon starting a new strip to the east of star
Delta…I suddenly spied a 15th magnitude
image…“That’s it,” I exclaimed to myself…I saw the
images almost instantly in a 1 by 2 cm field containing
about 300 stars…I had never encountered a planet
suspect so promising in all during all the fall months of
blinking…. I removed one of the plates and placed the
21 January plate [the one taken during miserable
weather] on the comparator. Sure enough, there was
the swollen image of Planet X exactly where it should
be…For three quarters of an hour, I was the only person
in the world who knew exactly the position of Planet
X ... ”.10
Pluto was observed 2.5 magnitudes (or ten times) fainter than Lowell had
predicted (Fig. 4). Tombaugh passed away in 1997; in a fitting memorial, some of
his ashes are on their way to Pluto aboard the New Horizons spacecraft (Fraknoi,
2009).
Figure 4. Two of the images used in the discovery of Plutoat the Lowell Observatory; Pluto is
marked with arrows (Fraknoi, 2009).
10 Tombaugh, 1986.
9
2.2.2 1977–1999: Closer to the Sun than Neptune (Habkkuk and the
Angel)11
At its apoapsis, Pluto goes as far as almost 49.3 AU from the Sun and
approaches it to almost 29.7 AU at its periapsis (Wikipedia). Pluto also has an
inclination of 17.14 degrees to the ecliptic. This interesting characteristic, as also
will be mentioned later in the text, causes Pluto to have a lopsided orbit which
brings it closer to the Sun than Neptune (Fig. 5). Such an event happens every
~248 years due to the planets orbital period. This already occurred during 1977
to 1999 (for a period of 22 years).
Figure 5. Pluto's orbit around the Sun (Ridpath, 1978).
11 Verses 33-39 in Bel and the Dragon (one of the additions to the book of Daniel in the Apocrypha) state that while in
Judea, Habakkuk is told by an angel to take the food he was making to Daniel who was in Babylon in the lion's den.
Habakkuk is then transported to the den by the angel. After giving the food to Daniel he is immediately taken back to
'his own place'.
10
2.2.3 1978: Discovery of Pluto's moon: Charon (Barbanito's Rage)12
Astronomers James Christy and Robert Harrington discovered in 1978 that
Pluto has an unusually large13 moon (NASA, 2012) which was consequently
named Charon (Fig. 6). On June 22, 1978, James Christy, while examining highly
magnified images of Pluto on photographic plates taken at the 61-inch Flagstaff
telescope two of months prior, noticed that a slight elongation appeared
periodically. Later, the bulge was confirmed on plates dating back to April 29,
1965 (Fig. 6).
(a)
(b)
(c)
Figure 6. (a) and (b) Photographs showing a bulge on the side of Pluto (inside the red circle in
(a) left), leading to the discovery of its moon, Charon (Pluto and Charon Lithograph, NASA,
2009). (c) Charon's orbit around Pluto.
12 In William Shakespeare's play Othello, Othello the Moor, a noble black warrior in the Venetian army, secretly marries a
beautiful white woman called Desdemona, the daughter of a prominent senator, Barbanito. When he finds out, he is
outraged, and promptly disowns her.
Pluto was discovered to have a moon 1978. Later on, with the discovery of several other moons, Pluto was crossed off
the list of planets.
13 Charon has a radius of 600km while Pluto's radius is measured as 1180km, which is only about twice as big (Pluto and
Charon Lithograph, NASA, 2009).
11
2.2.4 1988: Pluto has an Atmosphere (Die Zertanzten Schuhe)14
When a planet or other object passes in front of a star, any atmosphere
will distort and diminish the star's light in a characteristic way. For three decades
astronomers have sought to identify stars that lie directly in Pluto's path as seen
from the earth, but Pluto missed directly occulting any reasonably bright stars. A
brief flicker observed during a close brush by a star in 1980 apparently was
caused by Charon. A possible occultation in 1985 was obscured by poor observing
conditions. Pluto's exact position relative to stars has been difficult to predict
because of the wiggle in its motion caused by Charon's gravitational pull. Pluto's
uncertain diameter also has confounded astronomers attempting to predict
occultations (Binzel, 1990).
In 1985 Douglas J. Mink at Harvard University and Arnold R . Klemola at
lick Observatory identified a 12 magnitude star in the constellation Virgo that
seemed to lie directly in Pluto's path, and they predicted an occultation would
occur on June 9, 1988. Additional calculations by Lawrence H. Wasserman of
Lowell Observatory indicated that Pluto's shadow would fall on parts of Australia,
New Zealand and the South Pacific. Two teams of astronomers, led by Robert L .
Millis of Lowell Observatory and James L. Elliot and Edward W. Dunham of the
MIT, set out on expeditions torecord the occultation. They coordinated their
efforts with observatories in Australia, New Zealand and Tasmania (Fig. 7). In the
end, workers at eight sites obtained successful observations. The star did not
vanish abruptly as it slipped behind Pluto's disk but instead dimmed gradually.
Such behavior is characteristic of starlight being absorbed and refracted as it
passes through progressively deeper layers of an atmosphere. The light curve
showed a uniform, gradual dip as the star entered the top of Pluto's atmosphere
(Fig 8). As the star's image appeared to pass through the lowest levels of the
14
Originally written in German, The Twelve Dancing Princesses (Die Zertanzten Schuhe) tells
the story of 12 very beautiful princesses who
sleep in beds in the same room. Every morning they discover that their dancing shoes are worn even though they had not
used them and the door was locked. The king promises his kingdom and each daughter to any man who can discover the
princesses' midnight secret within three days and three nights, but those who fail within the set time limit will be put to
death.
Whilst traveling through the woods, an old soldier comes upon an old woman, who gives him an enchanted cloak that he
can use to observe them unawares and tells him not to eat or drink anything given to him in the evening by any of the
princesses and to pretend to be fast asleep until after they leave.
The story is similar to Pluto's atmosphere, which was looked for and debated for a long time and was looked for through
different methods.
12
atmosphere, however, the light curve dropped abruptly. Pluto seems to have a
clear upper-atmosphere overlying a more opaque lower layer. The boundary
between the two appears quite sharp (Binzel, 1990).
Figure 7. Astronomers at eight sites watched as Pluto passed in front of a
distant star on June 9, 1988 (Binzel, 1990).
Figure 8. The star dimmed gradually as its light entered the atmosphere. A sharp drop in the light curve (b and f),
observed on board the Kuiper Airborne Observatory, indicates a transition layer in Pluto's atmosphere. This may
be a low-lying haze or a region of rapid temperature change in the atmosphere (Binzel, 1990)
13
2.2.5 2005: Discovery of 2 additional moons (Yin and Yang)
Scientists using the Hubble Space Telescope announced in may 2005 the
discovery of two additional moons of Pluto. Named Nix and Hydra, the little
moons may have formed at the same time as Charon did, perhaps all three
splitting off from Pluto in a giant impact event. In February 2006, Hubble Space
Telescope confirmed the presence of these two new moons (Fig. 9).
Figure 9. Pluto, center and it's previously known moon Charon, below Pluto and right of center, shine brightly.
Two newly discovered moons appear more faintly to the right of the pair (NASA, 2006)
2.2.6 2006: New Horizons is Launched for Pluto (Neither snow Nor Rain
Nor Heat Nor Gloom of Night)15
In 2006, NASA dispatched an ambassador to the planetary frontier. The
New Horizons spacecraft is now halfway between Earth and Pluto, on approach
15 The Persian Royal Road was an ancient highway reorganized and rebuilt by the Persian king Darius the Great (Darius I)
of the Achaemenid Empire in the 5th century BC. Mounted couriers could travel 1677 miles (2699 km) in seven days;
the journey from Susa to Sardis took ninety days on foot. Herodotus wrote, "There is nothing in the world that travels
faster than these Persian couriers ... Neither snow nor rain nor heat nor gloom of night stays these couriers from the swift
completion of their appointed rounds.”
The New Horizons mission was launched in 2006 to visit Pluto and beyond and will arrive at Pluto in 2015 (just 2 years
later) and is moving on at the incredible speed of about 4 AUs a year.
14
for a dramatic flight past the icy planet and its moons in July 2015.
After 10 years and more than 3 billion miles (Fig. 10), on a historic voyage
that has already taken it over the storms and around the moons of Jupiter, New
Horizons will shed light on new kinds of worlds we've only just discovered on the
outskirts of the solar system (NASA, New Horizons web page).
Figure 10. The Countdown to New Horizon's approach to Pluto on its
web page (captured on June 12, 2013).
2.2.7. 2006: Pluto Is Excluded from the List of Planets (Prometheus
Bound)16
The International Astronomical Union classifies Pluto as a dwarf planet
and recognizes similar worlds beyond the orbit of Neptune as plutoids. This was a
16 Prometheus Bound is a play by Aeschylus(?) (c525 BC-c456 BC) in which Prometheus is punished by the gods for
stealing the fire (wisdom) and giving it to men. He was chained to a mountain in Caucasus.
After scientific discoveries about the pluto's moons and Kuiper belt which increased and changed our understanding of
the solar system, Pluto was excluded from the list of planets and pushed into the category of dwarf-planets.
15
consequence of the IAU re-definition of a planet (Resolution B5 – See Appendix II)
in 2006. IAU defined a planet and a so-called 'dwarf-planet' as:
*) A planet is a celestial body that
(a) is in orbit around the Sun,
(b) has sufficient mass for its self-gravity to overcome rigid body forces so
that it assumes a hydrostatic equilibrium (nearly round) shape, and
(c) has cleared the neighborhood around its orbit.
*) A "dwarf planet" is a celestial body that
(a) is in orbit around the Sun,
(b) has sufficient mass for its self-gravity to overcome rigid body forces so
that it assumes a hydrostatic equilibrium (nearly round) shape2,
(c) has not cleared the neighborhood around its orbit, and
(d) is not a satellite.
*) All other objects,except satellites, orbiting the Sun shall be referred to
collectively as "Small Solar System Bodies".
As a result, Pluto was labeled a dwarf-planet and was no longer
considered as a planet of the solar system. In spite of the controversies, Neptune
still remains the 8th and last planet in the solar system.
2.2.8 2011: A New Moon Is Discovered around Pluto (A River Flowed Out) 17
Astronomers (led by M. R. Showalter and D. P. Hamilton) using the Hubble
Space Telescope discovered a fourth moon orbiting the icy dwarf planet. The
satellite is located between the orbits of Nix and Hydra with an estimated
diameter ranging from 13 to 34 km (Pires dos Santos et al, 2011). This body is
temporarily called P4 (Fig. 11).
17 Book of Genesis describes the garden of Eden as “A river flowed out of Eden to water the garden, and there it divided
and became four rivers”.
Pluto was probably smashed into pieces from an originally larger body by a big impact, four of which were discovered
by 2011.
16
2.2.9 2012: Another Moon Is Discovered around Pluto (In a Cloud
of Dust and Smoke)18
Astronomers using the Hubble Space Telescope to search for potential
hazards to the New Horizon mission discovered a fifth moon orbiting the icy
dwarf planet. Due to the dwarf-planet concept, these bodies are no longer called
Pluto's moons officially, but they are rather called objects bound to Pluto. This
body is temporarily named P5 (Fig. 11).
Figure 11. Two new moons, P4 and P5, around Pluto (NASA, HST, 2012).
18 Title of a 2003 novel by Raymond Fraser. The idea for this novel came from a Fraser learning that a woman he knew
and had been in love years ago had survived and recuperated from a serious case of alcoholism in the same way he had.
With the discovery of new bodies around Pluto and the analysis of different astronomical data, it is concluded that the
Pluto system is a combination of objects with various sizes, ranging from dust particles to planet-sized bodies, probably
smashed by a big impact and put together later.
17
3. KNOWN FACT ABOUT PLUTO (MUCH ADO FOR NOTHING) 19
3.1 General Attributes (Take It or Leave It)
The very few major known characteristics of Pluto are listed below in
Table 1.
Table 1. Major Known Characteristic Values for Pluto.
Pluto Characteristics
Apoapsis *
48.871 AU
Periapsis *
29.657 AU
Sidereal Period of Revolutions **
90,465 days
Eccentricity **
0.253
Inclination to Ecliptic **
17.13°
Equatorial Radius **
1157 km
Mass ***
1.5 x 1022 km
Density ***
2.06 g/cm3
Albedo ***
0.61 (V)
Equatorial Gravity **
0.72 m/s2
Surface Temperature **
50 K
* Wikipedia ** Turcotte and Schubert (2002) *** Tholen et al (2008)
19 Not much is known about Pluto and we are all eagerly waiting for New Horizons spacecraft to reach its primary
destination.
18
3.2 Pluto Has Five Moons (On The Cross)20
As to June 2013, existence of 5 moons have been confirmed for Pluto and
it is predicted to have more, since Pluto seems to be more like a system of
particles rather than just one big body with much smaller bodies orbiting it. In
fact, a dust cloud is predicted to exist around Pluto (Pires dos Santos, et al,
2013).21
Major characteristic values for Pluto's moons are listed in Table 2.
Table 2 Major Known Characteristic Values for the Pluto System (Tholen et al, 2008)
Name
GM (km3/s2)
Mass (kg)
Density (g/cm3)
Diameter (km) Albedo (V)
Pluto
870.3±3.7
1.304x1022
2.06
2294
0.61
Charon
101.4±2.8
1.520x1021
1.63
1212
0.34
Nix
0.039±0.034
5.8x1017
1.63
88
0.08
Hydra
0.021±0.042
3.2x1017
1.63
72
0.18
Total
971.78±0.20 1.456x1022
2.01
-
-
Mechanical properties (Keplerian orbital elements) of the Pluto system
are listed in Table 3.
Table 3. Keplerian Orbital Elements, Epoch JD 2452600.5, Mean Equator and Equinox of J2000
(Tholen et al, 2008)
Name
a (km)
Charon# 19570.3
e
i (deg)
Ω (deg)
ω (deg)
0.0035
96.168
223.054
157.9
L (deg)
P (days)
257.960 6.38720
Nix##
49240.
0.0119
96.190
223.202
244.3
122.7
25.49
Hydra##
56210.
0.0078
96.362
223.077
45.4
322.4
38.85
# Plutocentric
## Barycentric
P4 and P5 are not listed in Table 2 and Table 3 since they have just been
20 In The HST pictures, the Pluto system is glowing like a cross. According to the New Testament, Jesus died as a result of
five wounds or scars. The Pluto view can remind one of the story (See Fig. 9 and Fig. 11).
21 Pluto is now considered as one of the many objects orbiting the sun in an area (ring) called the Kuiper belt.
19
discovered very recently and so little is known about them.
The fact that according to Table 2, Pluto and Charon are almost the same
size (Charon's diameter is almost half that of Pluto), causes Charon not to orbit
Pluto. In fact, Pluto here is not the main body and the two of them are orbiting
each other. In more correct words, they both orbit the center of gravity
(barycentre) of the system which in this case is not located inside the larger body
and is outside of them both (For a useful and more detailed discussion on
baricentric coordinates see Schindler and Chen (2012)).
The Pluto system is not just made up of two bodies, but there seem to be
a lot more, 4 other of which are now officially labeled as Pluto' moons. As a
matter of fact, the presence of many other bodies (many of which in the form of
dusty small particles) in the Pluto's environment (Fig. 13) is hypothesized to be a
result of the solar radiation pressure.
The increase in the instrumental accuracy in the observation of Pluto
along with the positioning of its satellites, caused the values for size
measurements for the planet to decrease over the years. As a result, after
decades of downward revisions, some astronomers whimsically noted that a
curve fitted to the plummeting estimates of Pluto's mass indicated that the
planet would vanish in 1980! Analyses of Charon's orbit finally revealed the
system's true mass, about 1/400 that of the earth (Fig. 12).
Figure 12.Estimated size and mass of Pluto initially were biased upward because some astronomers
erroneously thought Pluto's gravity was disturbing the orbits of Uranus and Neptune (Binzel, 1990). The
whimsical curve fit to the data points show that the Pluto system will vanish in around 1980!
20
Figure 13. Snapshots, viewed from the top in the barycentric reference frame, of dust launched from Nix
(in red) and Hydra (in green) for the grains radii 5 and 10μm. The positions of Charon, Nix and Hydra are
also indicated, and the time is shown on the top of each snapshot (Pires dos Santos, 2013).
21
3.3 Why Is Pluto Bright? (The Dragons Were Crying)22
Methane is abundant on Pluto, however, CH4 rapidly darkens in the
Plutonian solar insolation and charged particle environment. Therefore Pluto's
high albedo is at odds with the observation of methane frosts on Pluto's surface.
A variety of mechanisms exist to resolve this dilemma, and the result is that
Pluto's surface is being replenished with fresh (bright) volatile frosts (Fig. 14). This
replenishment is due to orbitally driven sublimation and freezeout of volatiles in
the atmosphere. Thus, Pluto's high albedo adds to the case for an atmosphere,
and argues for annual volatile transport cycles.
Figure 14. The evolution of Pluto's surface albedo resulting from the surface replenishment model. Here
"*"s represent dark polymers created by GCR bombardment (GCRPs) and "•"s represent UV photolysis
products (PPs). The six epochs depicted above form a time sequence: (a) the initial "clean" surface, (b) the
first approach to atmospheric maximum, (c) the first atmospheric maximum, (d) the following atmospheric
minimum, (e) an approach to atmospheric maximum after many orbits, and (f) an atmospheric maximum
after many orbits. Not shown are the mixing effects of micrometeoritic bombardment
22 The first chapter of Alison Goodman's book “The Neckless of the Gods” opens with the line “The dragons were crying”.
22
3.4 Orbit (Close Encounter of the Second Kind)
As mentioned above, Pluto is a many-body system of masses and not all of
them orbit around a common barycenter. Therefore its mechanical study is not
an analytical problem and is only possible through numerical solutions.
To solve the problem, Pluto’s system is described as an N+4-body problem
(Beauvalet et al, 2012). The number N refers to the bodies introduced in the
model that do not belong to Pluto’s system: the Sun and the eight planets, for
which the Moon’s mass is added to that of the Earth. The number 4 is for Pluto,
Charon, Nix and Hydra. The equations of motion of Pluto, Charon, Nix, and Hydra
are then calculated in an inertial reference frame centered on the barycenter of
the solar system, not a plutocentric one to avoid the additional inertial forces
(Only Pluto and Charon are described as oblate). As a result, Eq. 1 is a Newtonian
general description of a problem (Beauvalet et al, 2012):
Eq (1)
Eq (2)
23
where,
The solution to these equation system is not analytical.
3.5 Moon(s) (The Union Club Mysteries)23
Very little is known about the Pluto system, let alone each of the moons.
The dominant one, Pluto is only “speculated” to have a spherical shape. The same
is through for the next large body in the system, Charon (Fig. 15a and 15b). At the
same time some astronomers still believe Pluto to be an irregularly-shaped icy
body (Fig 16).
23 A series of short stories by Isaac Asimov.
24
(a)
(b)
Figure 15. (a) Pluto as observed by HST (HST albedo data, NASA). (b) Charon's Pluto-facing hemisphere
(determined from brightness variations during Pluto–Charon occultations), rendered by Celestia. Based on
mapping work done by Marc W. Buie.
Figure 16. Artist Anne Norcia's conception of Pluto (left) and Charon (top-right). Pixels are added to the picture to
add the concept of low resolution. Charon here also appears as an irregular body (modified from Ridpath, 1978).
Nix, Hydra, P4 and P5 are just discovered very recently and are so small
that we barely know nothing about them.24 The entire system is waiting for New
Horizons' visit in 2015.
24 A mystery wrapped in a riddle inside an enigma ...!
25
4. KUIPER BELT (THE WILD BUNCH)
The region of the solar system immediately beyond Neptune’s orbit is
densely populated with small bodies. This region, known as the Kuiper Belt,
consists of objects that may predate Neptune, the orbits of which provide a fossil
record of processes operative in the young solar system. The Kuiper Belt contains
some of the Solar System’s most primitive, least thermally processed matter. It is
probably the source of the short-period comets and Centaurs, and may also
supply collisionally generated interplanetary dust.
Edgeworth (1943) was the first to speculate on the existence of planetary
material beyond the orbit of Pluto. Referring to the solar nebula, he wrote, “It is
not to be supposed that the cloud of scattered material which ultimately
condensed to form the solar system was bounded by the present orbit of the
planet Pluto; it is evident that it must have extended to much greater distances.”
He also suggested that the trans-Plutonian region was the repository of the
comets: “From time to time a member of this swarm of potential comets
wanders from its own sphere and appears as an occasional visitor to the inner
regions of the solar system.” These qualitative ideas were later repeated by
Edgeworth (1949) and echoed by Kuiper (1951), who gave no indication that he
was aware of Edgeworth’s papers. The belt was later on observed not as a belt of
comets, but as a region (ring) of debris like bodies (Fig. 17)
Kuiper Belt objects (KBOs) are best identified by their slow, retrograde
(westward) motions when observed in the anti-solar direction. Then, the angular
velocity, dθ/dt [arcsec hr-1] is determined largely by parallax.
The bodies in the Kuiper belt approach Pluto in size. Major dwarf-planets
such as Haumea, Makemake and Eris (which is almost as large as Pluto) have
been identified in the belt.
26
Figure 17. Kuiper belt exhibitin Pluto and Eris in a view of the outer solar system (from Wikipedia)
5. NEW HORIZONS (LE LIVRE DES MERVEILLES)25
New Horizons spacecraft was launched on January 19, 2006, at 2:00 p.m.
EST from Cape Canaveral Air Force Station, Florida, USA. It weighs 385 kg and is
2.5 m wide. New Horizons runs on a 228 W radiothermal generator and is
carrying seven scientific instruments. It is scheduled to approach Pluto via Jupiter
gravity assist (Table 4).
25 Marvels of the World is a 13th-century travelogue written down by Rustichello da Pisa from stories told by Marco Polo,
describing Polo's travels through Asia, Persia, China, and Indonesia between 1276 and 1291 and his experiences at the
court of the Mongol leader Kublai Khan.
27
Table 4. New Horizons Scheduled Timeline.
Date
Body Approached
Occurred
2006 April 7
Mars
YES
2007 Feb. 28
Europa
YES
2007 Feb. 28
Jupiter
YES
2007 Feb. 28
Ganymede
YES
2007 Feb. 28
Callisto
YES
2007 Feb. 28
Io
YES
2008 June 8
Saturn
YES
2011 March 18
Uranus
YES
2014 August24
Neptune
NO
2015 July 14
Pluto
NO
2015 July 14
Charon
NO
2016 – 2020
Kuiper Belt
(extended mission)
NO
New Horizons will reach 100 AU from the Sun in December 203826. As is
seen from Table 4. It is now on its way to Neptune, but it is still a long way to go.
Its first sighting of Pluto in 2006 shows the planet as a small dot in the
background universe (Fig. 18). It's a huge universe after all!
With the discovery of new moons and objects in the Kuiper belt, many
new tasks have been proposed for New Horizons, a few of which have been
approved.
26 New Horizons Mission Objectives:
- Map surface composition of Pluto and Charon
- Characterize geology and morphology of Pluto and Charon
- Characterize the neutral atmosphere of Pluto and its escape rate
- Search for an atmosphere around Charon
- Map surface temperatures on Pluto and Charon
- Search for possible rings and additional satellites around Pluto
- Conduct similar investigations of one or more Kuiper Belt Objects
28
Figure 18. First sighting of Pluto by New Horizons in 2006 (NASA).
6. CONCLUSION
The conclusion to this manuscript is our eager waiting for the 2015 when
New Horizons will arrive at Pluto and provide us with good and accurate data on
the dwarf-planet. Pluto's unique mechanical and thermodynamic properties (e.g.
its moons, orbit, atmosphere, albedo, age, etc) have made it a very especial
object in the solar system.
29
References:
Alighieri, Danté, Inferno, The Divine Comedy, Translated by Longfellow, H.
W., Simon & Brown, 2013
Aristophanes, Plutus, 388 BC, translated by William Charles Green,
Whittaker & Co., 1892
Beauvalet L., Lainey V., Arlot J-E., Binzel R.P., Dynamical parameter
determinations in Pluto’s system*, Expected constraints from the New Horizons
mission to Pluto, Astronomy & Astrophysics, 2012.
Binzel, Richard P., Pluto, Scientific American, June 1990
David Jewitt, Kuiper Belt Objects, Annu. Rev. Earth. Planet. Sci, 1999
Edgeworth KE., The evolution of our planetary system, J. Br. Astron. Soc.,
1943
Edgeworth KE., The origin and evolution of the solar system. MNRAS, 1949
Hesiod, Theogony (8th - 7th century BC), 1st ed, edited by Brown N.,
Pearson, 1953
IAU, Resolution B5, Definition of a Planet in the Solar System, 2006
Kuiper GP., On the origin of the solar system, Astrophysics, ed. JA Hynek,
McGraw-Hill, 1951
Pires dos Santos, P.M. , Morbidelli, A., Nesvorný D., Dynamical capture in
the Pluto–Charon system, Celest Mec Dyn Astr, 2012
Pires dos Santos, P.M., Giuliatti Winter S.M., Sfair R., Mourão D.C., Small
particles in Pluto’s environment: effects of the solar radiation pressure, Monthly
Notices of Royal Astronomical Society, 2013.
Ridpath, Ian, Pluto – Planet or Imposter?, Astronomy, 1978
Schindler Max and Evan Chen, Barycentric Coordinates in Olympiad
Geometry, 2012
Stern, S. Alan, Ejecta exchange and satellite color evolution in the Pluto
system, with implications for KBOs and asteroids with satellites, Icarus, 2009
Stern, S. Alan, Trafton L.M., Gladstone G.R., Why is Pluto Bright?
Implications of the Albedo and Lightcurve Behavior of Pluto, Icarus, 1988
Sussman Gerald Jay, Wisdom J., Numerical Evidence that the Motion of
Pluto Is Chaotic, Science, 1988
Tholen David J., Buie M.W., Grundy W.M., Elliott G.T., Masses of Nix and
30
Hydra, The Astronomical Journal, 2008
Tombaugh, Clyde, Edited by: Andrew Fraknoi, The Discovery of Pluto:
Generally Unknown Aspects of the Story, Astronomy Beat, 2009
Young, L. A., Pluto's Seasons: The Predictions for New Horizons
31
APPENDIX I
Plutus (Play by Aristophanes)
Plutus is an Ancient Greek comedy by the playwright Aristophanes, first
produced in 408 BC, revised and performed again in c. 388 BC. A political satire
on contemporary Athens, it features the personified god of wealth Plutus.
Reflecting the development of Old Comedy towards New Comedy, it uses such
familiar character types as the stupid master and the insubordinate slave to
attack the morals of the time.
The play features an elderly Athenian citizen, Chremylos, and his slave
Cario or Carion. Chremylos presents himself and his family as virtuous but poor,
and has accordingly gone to seek advice from an oracle. The play begins as he
returns to Athens from Delphi, having been instructed by Apollo to follow the
first man he meets and persuade him to come home with him. That man turns
out to be the god Plutus — who is, contrary to all expectations, a blind beggar.
After much argument, Plutus is convinced to enter Chremylus' house, where he
will have his vision restored, meaning that "wealth" will now go only to those
who deserve it in one way or another.
The first part of the play examines the idea that wealth is not distributed
to the virtuous, or necessarily to the non-virtuous, but instead it is distributed
randomly. Chremylos is convinced that if Plutus' eyesight can be restored, these
wrongs can be righted, making the world a better place.
The second part introduces the goddess Poverty. She counters Chremylos'
arguments that it is better to be rich by arguing that without poverty there would
be no slaves (as every slave would buy his freedom) and no fine goods or luxury
foods (as nobody would work if everyone were rich).
After Plutus' eyesight is restored at the Temple of Asclepius, he formally
becomes a member of Chremylus' household. At the same time, the entire world
32
is turned upside-down economically and socially. Unsurprisingly, this gives rise to
rancorous comments and claims of unfairness from those who have been
deprived of their riches.
In the end, the messenger god Hermes arrives to inform Chremylus and
his family of the gods' anger. As in Aristophanes' The Birds, the gods have been
starved of sacrifices, since human beings have all directed their attention to
Plutus, and they no longer pay homage to the traditional Olympian gods. Hermes,
worried about his own predicament, actually offers to work for the mortals and
enters Chremylus' house as a servant on those conditions.
33
APPENDIX II
RESOLUTION B5
Definition of a Planet in the Solar System
Contemporary observations are changing our understanding of planetary
systems, and it is important that our nomenclature for objects reflect our current
understanding. This applies, in particular, to the designation "planets". The word
"planet" originally described "wanderers" that were known only as moving lights
in the sky. Recent discoveries lead us to create a new definition, which we can
make using currently available scientific information.
The IAU therefore resolves that planets and other bodies, except satellites, in our
Solar System be defined into three distinct categories in the following way:
(1) A planet* is a celestial body that
(a) is in orbit around the Sun,
(b) has sufficient mass for its self-gravity to overcome rigid body
forces so that it assumes a hydrostatic equilibrium (nearly round)
shape**, and
(c) has cleared the neighbourhood around its orbit.
(2) A "dwarf planet" is a celestial body that
(a) is in orbit around the Sun,
(b) has sufficient mass for its self-gravity to overcome rigid body forces so
* The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
** An IAU process will be established to assign borderline objects to the dwarf planet or to another category.
34
that it assumes a hydrostatic equilibrium (nearly round) shape2,
(c) has not cleared the neighbourhood around its orbit, and
(d) is not a satellite.
(3) All other objects***,except satellites, orbiting the Sun shall be referred
to collectively as "Small Solar System Bodies".
The IAU further resolves:
Pluto is a "dwarf planet" by the above definition and is recognized as the
prototype of a new category of Trans-Neptunian Objects ****.
*** These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs),comets, and other
small bodies.
**** An IAU process will be established to select a name for this category.
35
APPENDIX III
(On etymology of Pluto's satellites)
Charon
In Greek mythology, Charon or Kharon is the ferryman of Hades who
carries souls of the newly deceased across the rivers Styx and Acheron that
divided the world of the living from the world of the dead.
Charon, Inferno, Gustave Dore
36
Nix
The formal name "Nix", from the Greek goddess of darkness and night and
mother of Charon, was announced on June 21, 2006 on IAU Circular 8723 where
the designation Pluto II is also given. Together with Hydra (Pluto's third moon)
the initials are those of the New Horizons probe. The initial proposal was to use
the classical spelling Nyx, but to avoid confusion with the asteroid 3908 Nyx the
spelling was changed to Nix. The USGS Gazetteer of Planetary Nomenclature
states that Nix is the "Egyptian spelling" while Jürgen Blunck explains it as the
"Spanish translation" of the Greek name.[11]
Nyx, Ahmolean Meuseum, Oxford, UK, ca 425 – 375 BC
37
Hydra
The name Hydra was announced on June 21, 2006, in IAU Circular 8723
along with the formal designation Pluto III. The name is that of the Hydra, the
nine-headed serpent which battled Hercules in Greco-Roman Mythology. The
nine heads of Hydra are a reference to Pluto's tenure as the ninth planet; its
initial, H, refers to the Hubble Telescope which discovered Hydra and, together
with Nix, to the New Horizons mission whose safe passage was the motivation for
taking the Hubble images.
The Hydra and Heracles, ca6th B.C., J. Paul Getty Museusm, Malibu.
38
P4 & P5 -- Vulcan & Cerberus ?
The vote was open until February 25, 2013 at the CETI Institute
Voting for the naming of P4 and P5, Pluto's two new satellites. CETI Institute website, February 2013.
39
.