APOD: Charon and the Small Moons of Pluto (2015 Oct 26)

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APOD: Charon and the Small Moons of Pluto (2015 Oct 26)

Post by APOD Robot » Mon Oct 26, 2015 4:08 am

Image Charon and the Small Moons of Pluto

Explanation: What do the moons of Pluto look like? Before a decade ago, only the largest moon Charon was known, but never imaged. As the robotic New Horizons spacecraft was prepared and launched, other moons were identified on Hubble images but remained only specks of light. Finally, this past summer, New Horizons swept right past Pluto, photographed Pluto and Charon in detail, and took the best images of Styx, Nix, Kerberos, and Hydra that it could. The featured image composite shows the results -- each moon is seen to have a distinct shape, while underlying complexity is only hinted. Even though not satisfyingly resolved, these images are likely to be the best available to humanity for some time. This is because the moons are too small and distant for contemporary Earth-based telescopes to resolve, and no new missions to the Pluto system are planned.

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Re: APOD: Charon and the Small Moons of Pluto (2015 Oct 26)

Post by Ann » Mon Oct 26, 2015 5:46 am

Image
Well, who would have thought that Pluto is a retriever? He's been retrieving objects from all over the solar system!

Look! Nix looks just like a boulder from Ceres - it is dark, with some white markings. And Hydra is like another Comet 67P - it's a duck in space! (And Kerberos just might be another little 67P, too!)

What a menagerie! Pluto, where is Mickey, your master? Someone needs to keep an eye on you so you don't retrieve more objects from space!

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Re: APOD: Charon and the Small Moons of Pluto (2015 Oct 26)

Post by starsurfer » Mon Oct 26, 2015 7:58 am

It's great to see a comparison of all the moons, some of the newer ones might be unfamiliar to some.

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Re: APOD: Charon and the Small Moons of Pluto (2015 Oct 26)

Post by hoohaw » Mon Oct 26, 2015 9:38 am

Pluto has turned out to be far, far, more interesting than I had expected it would be. And now, for that reason, I am on tenterhooks as to what 2014 MU69 will surprise us with in four years or so!

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Re: APOD: Charon and the Small Moons of Pluto (2015 Oct 26)

Post by MarkBour » Mon Oct 26, 2015 10:35 pm

Both Nix and Hydra look like they could be typical comets or asteroids. They both look like they could easily be rocky bodies with some ice. If the inner planets were formed by conglomerations of such bodies, then there were lots of them that came into closer orbits of the Sun, as well as apparently many of them out in the Kuiper belt. How is it that the solar system came to be so abundant in these bodies? Did Sol pass through a region that already had an abundance of rocky material?
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Re: APOD: Charon and the Small Moons of Pluto (2015 Oct 26)

Post by neufer » Tue Oct 27, 2015 4:39 am

MarkBour wrote:
<<Both Nix and Hydra look like they could be typical comets or asteroids. They both look like they could easily be rocky bodies with some ice. If the inner planets were formed by conglomerations of such bodies, then there were lots of them that came into closer orbits of the Sun, as well as apparently many of them out in the Kuiper belt.>>
https://en.wikipedia.org/wiki/Kuiper_belt wrote:
<<The Kuiper belt is a region of the Solar System beyond the planets, extending from the orbit of Neptune (at 30 AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but it is far larger—20 times as wide and 20 to 200 times as massive. Like the asteroid belt, it consists mainly of small bodies, or remnants from the Solar System's formation. Although many asteroids are composed primarily of rock and metal, most Kuiper belt objects are composed largely of frozen volatiles (termed "ices"), such as methane, ammonia and water. Pluto is likely the largest and most-massive member of the Kuiper belt.

The Kuiper belt was initially thought to be the main repository for periodic comets, those with orbits lasting less than 200 years. However, studies since the mid-1990s have shown that the belt is dynamically stable, and that [periodic] comets' true place of origin is the scattered disc, a dynamically active zone created by the outward motion of Neptune 4.5 billion years ago; scattered disc objects such as Eris have extremely eccentric orbits that take them as far as 100 AU from the Sun.>>
https://en.wikipedia.org/wiki/Hydra_%28moon%29#Name wrote:
<<The name Hydra was announced on 21 June 2006. The name is that of the Hydra, the nine-headed serpent that battled Hercules in Greek 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.>>
https://en.wikipedia.org/wiki/Lernaean_Hydra wrote:
The Lernaean Hydra, more often known simply as the Hydra, was an ancient serpentine water monster with reptilian traits. Its lair was the lake of Lerna in the Argolid. Lerna was reputed to be an entrance to the Underworld and the Hydra served as a guard.

According to Hesiod, the Hydra possessed many heads ("more than the vase-painters could paint") and, each time one was lost, it was replaced by two more. It had poisonous breath and blood so virulent that even its scent was deadly.

Eurystheus sent Heracles to slay the Hydra, which Hera had raised just to slay Heracles. Upon reaching the swamp near Lake Lerna, where the Hydra dwelt, Heracles covered his mouth and nose with a cloth to protect himself from the poisonous fumes. He shot flaming arrows into the Hydra's lair, a deep cave from which it emerged only to terrorize neighboring villages. The chthonic creature's reaction to decapitation was botanical: two grew back, an expression of the hopelessness of such a struggle for any but the hero. The weakness of the Hydra was that it was invulnerable only if it retained at least one head.

Heracles called on his nephew Iolaus for help. Heracles cut off each head and Iolaus cauterized the open stumps. Seeing that Heracles was winning the struggle, Hera sent a large crab to distract him. He crushed it under his mighty foot. The Hydra's one immortal head was cut off with a golden sword given to Heracles by Athena. Hera, upset that Heracles had slain the beast she raised to kill him, placed it in the dark blue vault of the sky as the constellation Hydra. She then turned the crab into the constellation Cancer.

When Eurystheus, the agent of Hera who was assigning The Twelve Labors to Heracles, found out that it was Heracles' nephew Iolaus who had handed Heracles the firebrand, he declared that the labor had not been completed alone and as a result did not count towards the 10 labors set for him. The mythic element is an equivocating attempt to resolve the submerged conflict between an ancient ten labors and a more recent twelve.>>
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Re: APOD: Charon and the Small Moons of Pluto (2015 Oct 26)

Post by MarkBour » Tue Oct 27, 2015 9:54 pm

Thanks for those facts, and the mythology as well. I'm still wondering, though. I had in my head a basic theory of the formation of the Solar system. That a cloud of dust and gas coalesced to form both Sol and the planets, etc. I pictured an accretion disk that formed and everything else came from it. (Such as: http://csep10.phys.utk.edu/astr161/lect ... bular.html) I have not yet read any more involved theories that might be informed by many more facts than I have considered.

Something feels wrong, intuitively, though with that, as I learn more about the Kuiper belt objects. Perhaps there was an additional population of objects, which did not just coalesce with Sol. Perhaps our sun has simply captured a lot of them that were in its surrounding area, and perhaps it is actually passing through a local region with many objects and picking up more as it goes. I suppose the solar wind may also be pushing some away, as well.

Perhaps one of the contributors knows reasons to either like or dislike this notion of a significant population of other objects. Perhaps, without far more detailed data, the question is idle speculation, unable to be settled.
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Re: APOD: Charon and the Small Moons of Pluto (2015 Oct 26)

Post by starsurfer » Wed Oct 28, 2015 7:55 am

MarkBour wrote:Both Nix and Hydra look like they could be typical comets or asteroids. They both look like they could easily be rocky bodies with some ice. If the inner planets were formed by conglomerations of such bodies, then there were lots of them that came into closer orbits of the Sun, as well as apparently many of them out in the Kuiper belt. How is it that the solar system came to be so abundant in these bodies? Did Sol pass through a region that already had an abundance of rocky material?
They remind me of the moons of Mars, Phobos and Deimos, which I think are also captured asteroids.

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Re: APOD: Charon and the Small Moons of Pluto (2015 Oct 26)

Post by geckzilla » Wed Oct 28, 2015 9:45 am

Unless I'm mistaken, the Kuiper belt objects such as Pluto and its moons are thought be of starkly different composition than many asteroids, specifically the ones of the asteroid belt. It was for this reason that Pluto and the whole debate of planethood came about. They're different enough to warrant a category of their own.

Of course, it is also possible that some objects such as Pluto and its moons share characteristics with asteroids while some other cometary objects and other Kuiper belt objects are on some further end of the spectrum.
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