APOD: Pluto's P4 (2011 Jul 22)

[areinheimer]

It seems amazing that Hubble can pick out something 13-34 km across at a distance of 4.2? 7.5? billion km. That's something smaller than the area of Los Angeles, seen from several billion miles away. It brings home just how powerful the telescope really is.

[neufer]

It seems amazing that Hubble can pick out something 13-34 km across at a distance of 4.2? 7.5? billion km. That's something smaller than the area of Los Angeles, seen from several billion miles away. It brings home just how powerful the telescope really is.

"That's something smaller than the area of Los Angeles,
seen from several billion miles away"
as illuminated by a distant sun several billion miles away

P4 apparent magnitude: ~26

Pluto apparent magnitude: ~14

[Orca]

Now bring back Pluto as a planet catagory that the Astronomy says it (Pluto) is not!

I don't know what "Astronomy" is in this context.

Pluto is still a "planet" as most people use the word, and still a "planet" to most astronomers. The IAU (which certainly has no official standing to define any words, but merely makes recommendations for usage by professional astronomers) has produced a convoluted definition for "planet" which is illogical and ambiguous in the case of Pluto (how can a "dwarf planet" not also be a "planet"?) But there is nothing stopping you, or anybody else, from calling Pluto a planet. I certainly do, and I call it a planet when I discuss the matter with my students.

Given the inadequacies of the current IAU definition, it is nearly certain that we'll see additional, probably substantial changes in the future.

I don't think the definition provided by the IAU is that bad. Of course, as we are learning from our discoveries of extrasolar planetary systems, planets can come in many more flavors than we had ever imagined.

Granted, this all comes down to semantics rather than science (as you've pointed out in the past Chris). To me, the question is: how much import do we want to give the term "planet?" Either we have 8 planets and n dwarf planets, or we have n planets.

Ultimately, in terms of science, whether you are discussing Pluto or Mars, "planetary status" hasn't got any bearing at all.

[itwasnoteasy]

Strange revolution pattern around pluto
I noticed the direction of revolution of the other three moons including the new P4 is anticlockwise but direction of Charon is clockwise from the images they have posted. (Jun-28 and July-11)

Or, is there something else which needs to be considered? Am I missing something?

[bystander]

Strange revolution pattern around pluto
I noticed the direction of revolution of the other three moons including the new P4 is anticlockwise but direction of Charon is clockwise from the images they have posted. (Jun-28 and July-11)

Or, is there something else which needs to be considered? Am I missing something?

Yes, Charon is orbiting a lot faster.

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http://asterisk.apod.com/viewtopic.php? ... 31#p153031

[neufer]

And I have to think about it for a while, but changing it from a hellish name to the heavenly one of Snow White, with her dwarfs for moon names is worth considering.

Plutinos in 2:3 orbital resonance with Neptune

Except for the fact that:

"Pluto [is] one of the reddest bodies in the Solar system
due to the effects of sunlight on the nitrogen and methane ices of its surface"

<<Rose Red (or Rose-Red) is a character in the fairy tale Snow-White [CHARON] and Rose Red [PLUTO], recorded by the Brothers Grimm. She is the sister of Snow-White, not to be confused with Snow White. Of the two, Rose Red is portrayed as the more rambunctious of the two devoted sisters, associated with the summer as Snow White is with the winter.

The story of Rose Red and Snow White features evil dwarves [NIX, P4 & HYDRA] and a bear who becomes a prince. Snow White marries this prince, and Rose Red marries his brother. The story also features a kindly mother who tells the two sisters that they must share between the two of them all that they have. This story is unrelated to the Snow White tale popularized in modern times by the Walt Disney film Snow White and the Seven Dwarfs.>>

[b][color=#0000FF][size=115]Nix, P4 & Hydra are very close to a 1:4:5:6 orbital resonance[/size][/color][/b]

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<<It is suspected that the Plutonian satellite system was created by a massive collision, similar to the "big whack" believed to have created the Earth's Moon. In both cases it may be that the high angular momenta of the moons can only be explained by such a scenario. The nearly circular orbits of the smaller moons suggests that they were also formed in this collision, rather than being captured Kuiper Belt objects. This and their near orbital resonances with Charon suggest that they formed even closer to Pluto than they are at present, and that they migrated outward as Charon achieved its current orbit. If Hydra and Nix turn out to be tidally locked, as Charon is, that will settle the issue, as tidal forces are insufficient to damp their rotations in their present orbits. The color of each is a lunar grey like Charon, which is consistent with a common origin. Their difference in color from Pluto, one of the reddest bodies in the Solar system due to the effects of sunlight on the nitrogen and methane ices of its surface, may be due to a loss of such volatiles during the impact or subsequent coalescence, leaving the surfaces of the moons dominated by water ice. Such an impact would be expected to create additional debris (more moons), but these must be relatively small to have avoided detection by Hubble. It is possible that there are also undiscovered irregular satellites, which are captured Kuiper Belt objects.

Nix, S/2011 (134340) 1 and Hydra are very close to a 1:4:5:6 orbital resonance with the Charon-Pluto orbital period: Nix is within 2.7% of resonance, S/2011 (134340) 1 is apparently within 0.6%, while Hydra is within 0.3%, though none appear to be in an exact resonance. It may be that these orbits originated as forced resonances when Charon was tidally boosted into its current geosynchronous orbit, and then released from resonance as Charon's orbital eccentricity was tidally damped. Today the Pluto–Charon pair continue to produce strong tidal forces, with the gravitational field at the outer moons varying by 15% peak to peak. At the lower estimated size range, Nix should have no significant precession, while Hydra should have a precession period of 15 years. However, at their maximum projected masses (assuming an albedo of 4%), the two moons may be in a 3:2 orbital resonance with each other, with libration periods of 400 to 450 days, though this may already be ruled out by the low eccentricity of Charon. Thus accurate orbital data can help resolve the sizes of these moons.

However, it was recently calculated that a resonance with Charon could boost either Nix or Hydra into its current orbit, but not both: boosting Hydra would have required a near-zero Charonian eccentricity of 0.024, while boosting Nix would have required a larger eccentricity of at least 0.05. This suggests that Nix and Hydra were instead captured and migrated inward until they were trapped in resonance with Charon.>>

[Chris Peterson]

I don't think the definition provided by the IAU is that bad.

I disagree. If a "dwarf planet" isn't a "planet", the definition violates the most basic principles of English!

Of course, as we are learning from our discoveries of extrasolar planetary systems, planets can come in many more flavors than we had ever imagined.

By the IAU definition, there are no confirmed extrasolar planets- because the definition is so absurdly limited. A good definition would have allowed for all the bodies in our own system, as well as the extrasolar bodies we've discovered. As we refine our classifications, it is those classifications that require definition or redefinition, not "planet" itself.

To me, the question is: how much import do we want to give the term "planet?" Either we have 8 planets and n dwarf planets, or we have n planets.

Those aren't the only options. We can have hundreds of planets, which are broken down into terrestrial, gas giant, icy, asteroidal, dwarf, etc.

[saturn2]

P4 is a new satellite of Pluto.
I think Pluto is a planet.
I was very sad when Pluto lost the planet status.

[orin stepanek]

I agree with Chris. If I were a traveler from another system; How would I describe our system?

[Boomer12k]

Excuse ME?!?!?!?!

BUT ANYTHING WITH FOUR PHRICKEN MOONS IS A FULL FLEDGED PLANET!!!!!!!!!!!!!!!!!!!!!!!!!!! END OF DISCUSSION!!!!!!!!!!
OK, maybe it does not fulfill all of the definitions, that just means, our EVALUATIONS are not totally correct. Like allot of things.
I think we need to maybe make a special case. "Full Planet Rights" for Pluto!

:----========

[islader2]

The name of the satellite Charon does not have anything to do with Hades. Charon is a scienficized name created by Christy for his wife Char==one of the most romantic tales in science. If Pluto is not a planet, let us honor Christy and his beautiful tale of uxorial eternal love by pronouncing the name properly: sha-ron, not ky-ron.

[ExplorerAtHeart]

Don't forget about Eris

[orin stepanek]

Don't forget about Eris

Eris and a few others

Click to view full size image

[neufer]

[b][color=#0000FF]'[i]Fluffy[/i]' guarding the Royal Institute of Technology in Stockholm.[/color][/b]

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<<Fluffy is a giant three-headed dog provided by Hagrid to guard the trapdoor leading to the underground chamber where the Philosopher's Stone was hidden. The only known way to get past Fluffy is to lull him to sleep by playing music. Fluffy is based on Cerberus, the three-headed dog from Greek Mythology that guards the gates to the underworld. In Philosopher's Stone, Harry, Ron, Hermione and Neville accidentally run into Fluffy whilst hiding from Peeves, who was attempting to give them away to caretaker Argus Filch, who was searching for them. On Halloween, Harry and Ron witness Snape entering the door to Fluffy's chamber, and for the next few days having a pronounced limp. Harry also overhears him saying "How are you meant to keep your eyes on all three heads at once?" to Filch. However, it is later revealed that he followed then Hogwarts Defence Against the Dark Arts professor Quirinus Quirrell into the chamber. While Fluffy is guarding the Philosopher's Stone, Professor Quirrell penetrates Fluffy's defences by playing a harp, in order to access the trapdoor, while Harry uses a flute that had been given to him by Hagrid. As with Fluffy, Cerberus was lulled to sleep with music by Orpheus. Rowling was asked in an interview what happened to Fluffy after he was no longer needed to protect the Stone. Her reply was that Fluffy was released into the Forbidden Forest.>>

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What Should We Name Pluto's New Moon?
Fox News July 23, 2011

<<A fourth moon orbiting the dwarf planet Pluto has just been discovered. The tiny satellite — it's a mere 8 to 21 miles (13 to 34 km) across — showed up as a faint dot on new, long-exposure photos of the Pluto system taken by NASA's Hubble Telescope.

But enough with the technical details: What will we call the newest member of the solar community?

"It's called P4 for the time being," said Trent Perrotto, public affairs officer at NASA headquarters. "It'll get a name, but it's not up to NASA to decide on it." As usual with newly discovered astronomical objects, he explained, P4's name will be subject to a tough selection process overseen by an organization called the International Astronomical Union.

In an unofficial Facebook poll of SPACE.com readers, the top choice is "Mickey." Unfortunately for them, though, this won't satisfy the IAU's official naming conventions. According to the IAU guidelines, "Objects crossing or approaching the orbit of Neptune … notably [Pluto and its moons], are given mythological names associated with the underworld."

Pluto was the god of the underworld in Roman mythology. Charon, Pluto's largest moon, is named after the ferryman who carried the souls of the newly deceased across the River Styx, which divided the world of the living from that of the dead. Nix, Pluto's second moon, was the Greek goddess of darkness and night, and Charon's mother. Hydra, the third, was a many-headed serpent that guarded a back entrance to the underworld located deep below the surface of a lake.

In choosing a name along these hellish lines for P4, the IAU nomenclature committee will try to honor the wishes of its discoverer: planetary astronomer Mark Showalter of the SETI Institute in California. What's his choice? "This is a topic under discussion," Showalter told Life's Little Mysteries. "We have a lot of colorful names to choose from because all the moon names come from, essentially, the minions of Hades. One name that seems to come up most is Cerberus, the dog who guards the gates to hell." Three-headed Cerberus is Hydra's sibling.

"Cerberus: How could you go wrong with a name like that?" Showalter said. "But, unfortunately, Cerberus is already the name of an asteroid. The IAU balks at the idea of using asteroid names, although it's not necessarily out of the question. Even then, Kerberos, [the spelling that] is closer to the original Greek, would be OK even if Cerberus is not. I don't want to say that's the name we've chosen. There are a lot of interesting names being discussed."

Showalter and his discovery team will submit their top choices to the IAU soon, and he thinks they'll choose a name within two months. Perhaps Cerberus/Kerberos will soon be guarding the Kuiper Belt.>>

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[img3="Cerberus held in the grasp of Hercules, as shown on the Firmamentum Sobiescianum star atlas of Johannes Hevelius (1687). Cerberus is sometimes substituted for the "branch from the tree of the golden apples" fetched by Atlas from the garden of the Hesperides. This branch is the literary source of
the "golden bough" in the Aeneid by Virgil.
Image © Tartu Observatory Virtual Museum."]http://www.ianridpath.com/startales/ima ... rberus.JPG[/img3]

<<Cerberus, or Kerberos, (Greek: Κέρβερος) is a multi-headed hound which guards the gates of The Underworld, to prevent those who have crossed the river Styx from ever escaping. Cerberus featured in many works of ancient Greek and Roman literature and in works of both ancient and modern art and architecture, although, the depiction and background surrounding Cerberus often differed across various works by different authors of the era. The most notable difference is the number of its heads: Most sources describe or depict three heads; others show it with two or even just one; a smaller number of sources show a variable number, sometimes as many as 50.

"Cerberus" is generally pronounced in English with a soft C as in cell, even though the ancient pronunciation, in both Greek and Latin was with a hard C as in cat. The name may be related to the Sanskrit word सर्वरा "sarvarā", used as an epithet of one of the dogs of Yama, from a Proto-Indo-European word *ḱerberos, meaning "spotted." Certain experts believe that the monster was inspired by the golden jackal.

Cerberus is said to be the sibling of the Lernaean Hydra, the Nemean Lion, the Sphinx, the Ladon, and the Chimera. Cerberus was the offspring of Echidna, a hybrid half-woman and half-serpent, and Typhon, a fire-breathing giant whom even the Olympian gods feared. Its brother is Orthrus, always depicted as a two-headed hellhound. The common depiction of Cerberus in Greek mythology and art is as having three heads, a mane of live serpents (similar to Medusa's hair) and a snake's tail. In most works the three-heads each respectively see and represent the past, the present, and the future, while other sources suggest the heads represent birth, youth, and old age. Each of Cerberus' heads is said to have an appetite only for live meat and thus allow the spirits of the dead to freely enter the underworld, but allow none to leave. Cerberus was always employed as Hades' loyal watchdog, and guarded the gates that granted access and exit to the underworld (also called Hades).

Capturing Cerberus alive, without using weapons, was the final labour assigned to Heracles (Hercules) by King Eurystheus, in recompense for the killing of his own children by Megara after he was driven insane by Hera, and therefore was the most dangerous and difficult. In the traditional version, Heracles would not have been required to capture Cerberus, however Eurystheus discounted the completion of two of the tasks as Heracles had received assistance.

After having been given the task, Heracles went to Eleusis to be initiated in the Eleusinian Mysteries so that he could learn how to enter and exit the underworld alive, and in passing absolve himself for killing centaurs. He found the entrance to the underworld at Tanaerum, and Athena and Hermes helped him to traverse the entrance in each direction. He passed Charon with Hestia's assistance and his own heavy and fierce frowning.

Whilst in the underworld, Heracles met Theseus and Pirithous. The two companions had been imprisoned by Hades for attempting to kidnap Persephone. One tradition tells of snakes coiling around their legs then turning into stone; another that Hades feigned hospitality and prepared a feast inviting them to sit. They unknowingly sat in chairs of forgetfulness and were permanently ensnared. When Heracles had pulled Theseus first from his chair, some of his thigh stuck to it (this explains the supposedly lean thighs of Athenians), but the earth shook at the attempt to liberate Pirithous, whose desire to have the wife of a god for himself was so insulting he was doomed to stay behind.

Heracles found Hades and asked permission to bring Cerberus to the surface, which Hades agreed to if Heracles could overpower the beast without using weapons. Heracles was able to overpower Cerberus and proceeded to sling the beast over his back, dragging it out of the underworld through a cavern entrance in the Peloponnese and bringing it to Eurystheus. The king was so frightened of the beast that he jumped into a pithos, and asked Heracles to return it to the underworld in return for releasing him from his labors.

Cerberus featured in many prominent works of Greek and Roman literature, most famously in Virgil's Aeneid, Peisandros of Rhodes' epic poem the Labours of Hercules, the story of Orpheus in Plato's Symposium, and in Homer's Iliad, which is the only known reference to one of Heracles' labours which first appeared in a literary source. Most occurrences in ancient literature revolve around the basis of the threat of Cerberus being overcome to allow a living being access to the underworld; in the Aeneid Cerberus was lulled to sleep after being tricked into eating drugged honeycakes and Orpheus put the creature to sleep with his music. In Dante Alighieri's Inferno, Canto VI, the "great worm" Cerberus is found in the Third Circle of Hell, where he oversees and rends to pieces those who have succumbed to gluttony, one of Roman Catholicism's seven deadly sins. In Paradise Lost11.65, Cerberean hounds are mentioned in Hell: "A cry of Hell Hounds never ceasing bark'd With wide Cerberean mouths full loud".>>

Orthrus Neuendorffer

[Leon1949Green]

Thanks, neufer, lol! Is there something near Charon that could be the mirror? A "reflection" nebula, perhaps?

[bystander]

What Should We Name Pluto's New Moon?
Fox News July 23, 2011

http://asterisk.apod.com/viewtopic.php? ... 61#p153161

[Rueda]

I suggest a name for P4, Pauline
Thanks!

[pgp566]

I agree with everything that's gone before - Pluto is most clearly orbiting the Sun and since it has enough mass to acquire no less than _four_ moons it is most obviously a planet. Time to reverse the decision guys! - embarrassing though this will be ... I always felt that this was some kind of techno-geek decision with headline-grabbing intent. OK, three of the moons are very small, but not even the earth has managed to capture asteroid-sized moons whereas Pluto has!