The Strangest Moon In the Solar System 141
StartsWithABang writes Moons in our Solar System — at least the ones that formed along with the planets — all revolve counterclockwise around their planetary parents, with roughly uniform surfaces orbiting in the same plane as their other moons and rings. Yet one of Saturn's moon's, Iapetus, is unique, with a giant equatorial ridge, an orbital plane that doesn't line up, and one half that's five times brighter than the other. While the first two are still mysteries, the last one has finally been solved.
Re:That's no moon! (Score:5, Funny)
They promise to only look at our metadata, not the content of our cell calls and digital pictures.
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Actually that's a mistranslation, it should be:
They promise to only look at our metadata, not the content of our glial cells and mental pictures.
Medium. (Score:5, Informative)
Linking to Medium is the new linking to LiveJournal.
Re:Medium. (Score:5, Insightful)
After all, we could have links to scientific papers or at least their abstracts written by actual scientists who studied the phenomena.
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TL;DR
Besides, it's PICTURES!
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...and text 2-3x larger than it needs to be. Had to press Ctrl-- a few times to get it back down to roughly what every other website uses. Are they writing for the semi-blind?
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How appropriate that this is the Starts with a Bang blog: way too many sentences in the postings on this site end with a bang.
... one half of Iapetus is only about one-fifth as bright as the other!
But one of them has!
... density of about seven dust-sized grains per cubic kilometer!
... and finally know why it has a yin-yang coloration unlike anything else!
Zowie! Boom! Kablooie!
These articles read like a comic book. When I'm looking for scientific details, the style of these articles is really offputting.
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Yet another reason to put a tax on the exclamation point.
Counterclockwise? (Score:1, Insightful)
Viewed from which side? Counterclockwise does not apply here.
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Viewed from which side? Counterclockwise does not apply here.
Viewed when looking down from the north pole. This is mentioned in TFA, per
Rather that [sic] (looking down from the north pole) orbiting counterclockwise around its parent planet, which all the other moons do, Phoebe revolves clockwise around Saturn.
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But which way is north?
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But which way is north?
Up
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The angular momentum imparted by the planetoid caused Venus to "flip".
Wouldn't it keep rotating? Why would it flip end-to-end and then stop?
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Re:Counterclockwise? (Score:5, Informative)
Towards Polaris, and in fact that gives the direction of "galactic north" too. Note due to precession of Earth's axis after 3000 AD Gamma Cephei will become the pole star, and Iota Cephei in 5200 AD. Thuban was the pole star in 3000 B.C. Polaris will again become the pole star about 27,800AD
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The planets are all in more or less the same plane, so the concept of north is meaningful throughout the system.
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Yes, agreed for most planets... but what about Uranus?
(serious question, since it rotates sideways on its axis)
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Australia isn't the only place in the southern hemisphere
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Re:Counterclockwise? (Score:5, Informative)
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The only planet whose north pole is not on the same side of the Ecliptic as the Earth's north pole is Uranus.
Venus's axial tilt is 177 degrees, that's about "not on the same side of the Ecliptic" as it could be.
Re:Counterclockwise? (Score:5, Interesting)
According to the IAU definition [usgs.gov], the north pole for a major planet (or one of its satellites) is the pole on the same side of the ecliptic as the Earth's north pole, the North Celestial Hemisphere. By this definition, Venus and Uranus are retrograde rotators -- they rotate clockwise about their north poles.
For comets and minor planets (including Dwarf planets), the north pole is the pole about which the body rotates counterclockwise. So the north pole of a retrograde-rotating asteroid points into the South Celestial Hemisphere.
This brings us (as do all topics that mention the IAU) to Pluto. Pluto rotates retrograde. It was once considered a major planet, so it's north pole would have been on the same side of the ecliptic as ours. But as a dwarf planet, the opposite definition applies. Even before the 2006 decision, the convention was inconsistently applied. Papers have been published using each definition of the north pole, and they're not always good about stating which convention they used. With New Horizons on the doorstep, we're going to need consistency for mapping and navigation. So I believe the mission has decided to use the current IAU definition consistently to avoid any confusion. There was a huge fight over the coordinate system of Vesta on the Dawn mission, and we don't want that.
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"North" is a geocentric concept that can be projected outward upon the solar system.
That one is simple and easy since there is a clear consensus among Earth dwellers as to which way is north.
In other situations it can get more complicated, such as when projecting the egocentric concept of "Left" and "Right" outward from an individual point of view. The simplest case is when looking at a photo of Mutt and Jeff, and being told that Mutt is on the left. Even though when the photo was taken both Jeff would ha
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Down is pretty consistent as it is always towards the center of gravity.
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Viewed from which side? Counterclockwise does not apply here.
Almost planets and their moons orbit in, or closely aligned to a single plane (the ecliptic). Looking "down" (from the North) on a tangent to that plane, the planets and satellites will be seen to be rotating clockwise as most of their axes are also more or less perpendicular to that plane.
Re:Counterclockwise? (Score:4, Informative)
Or just use the right hand rule :) Where "north" is by definition the positive direction of the total angular momentum pseudo-vector of the solar system.
Medium site full of cloudfront trackers (Score:1)
Every single hash-laden cloudfront link is a tracker. No thanks, Medium.
The strangest moon in the solar system is ours. (Score:5, Informative)
It's HUGE.
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It's not a moon so it doesn't count.
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Our moon is not a moon? Sorry?
(BTW I know that there are bigger moons than ours, but they're moons of Jupiter FFS).
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It was a Star Wars IV reference/joke.
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You should only make jokes about episodes I, II and III.
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Technically, the moon isn't *yet* a planet, but will be in a few millions of years.
There is no "technically" in this case, as there is no formal definition of a double planet. Some people think the barycenter moving above the surface is the definition of a double planet, but that is in no way formal or "technically." Plenty of astronomers think that definition is not very useful, because changing distance between two bodies can always move the barycenter out of the surface of the larger one, while not changing the dynamics in any qualitative way. Jupiter already moves the barycenter of
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Considering Venus the only other planet sized similarly to Earth in this solar system, and that we don't know of any exomoons yet, it seems premature to declare it that unusual.
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Indeed.
This makes me think of "Foundation and Earth" by Isaac Asimov.
~30,000 years in the future, and they're looking for the mythical homeworld of humanity, known as "Earth".
But the legends about the huge moon and the gas giant with a huge ring system are obviously just legends, exaggerated over the milennia, and should not be taken seriously...
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Our moon is not a moon? Sorry? ...
The Earth's "moon" is not a moon, the Earth-Moon system is a double planet. At no point does the Moon's orbit actually curve away from the Sun, it always curves toward the Sun. As it goes on the "inside" of the orbit it flattens out, but does not curve away from the Sun.
In other words, the moon is influenced more by the Sun's gravity, than the Earth's gravity.
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named Dahak.
That's true, but if you tell anyone else I will just claim I was kidding with you... 8-)
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I'm not sure why you're modded funny. The relative sizes of the Earth/Moon system is a total anomaly, so much so that it is very very close to the point where you have to call them a double planet rather than a planet and moon.
Re:The strangest moon in the solar system is ours. (Score:4, Interesting)
There is also the bizzare coincidence that the size of our moon, viewed from the earth is almost exactlty the same as the sun, viewed from the earth -- hence total eclipses of the sun.
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The moon has been receding from the earth since its creation. The coincidence is that we are here to observe the moon during the time when the visual sizes are so similar.
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Coincidence eh? Or is it that God wanted us to explore our world...
"The Moon is unique in the solar system in its large relative size compared with the Earth. The Moon appears from the Earth to be the same size as the sun, in perfect artistic symmetry, unlike any known other planet-moon system. [...] To many Christians, these characteristics appear as "clues" or "hints" left by God for men to discover. [...] The Moon appears to have the same size as the Sun when viewed from Earth. This creates a unique symm
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The problem with those events with a small probability is that there are so many of them that a few will always occur. It's like saying that god is responsible for the lottery winner because the probability of each player is very low.
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There is a possibility a large moon is necessary for intelligent life, or at the least the strong tides (really huge at the beginning) were helpful in stirring things up for the appearance of dumb life.
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It's a possibility. It attracts a fair amount of discussion. With a sample size of 1, we have no way of assessing whether or not it's a true statement. It is just as likely that the development of life, and intelligence, are completely unrelated to the presence of a medium-size moon.
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Is it? Moon diameter is 0.2724 that of Earth ; Charon's diameter is 0.5050 that of Pluto. For masses the corresponding ratios are 0.0122 (1/81) and 0.1160 (1/9). so, is the Moon a "total anomaly"?
I've been taking an interest in astronomy for 40 odd years now, and I don't know what the point where I'd "have to" call a syste
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That's no moon; that's half a binary planet.
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Unique? (Score:5, Insightful)
Yet one of Saturn's moon's, Iapetus, is unique
Aren't they all unique?
Re:Unique? (Score:5, Funny)
Yet one of Saturn's moon's, Iapetus, is unique
Aren't they all unique?
Yes, and they're all special too.
And they can grow up to be any kind of planet they want.
AS LONG AS IT'S A DWARF PLANET, RIGHT PLUTO? HA HA HA, LOSER!
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No, only Iapetus is unique. All the other moons are the same, but Iapetus isn't. That's the one thing that makes it different from the rest.
To summarize. (Score:2, Informative)
I found this article to be rather long winded in order to create a story with suspense.
The moon has a side facing away from Saturn which is darker then the side facing saturn. It seems to be due to collecting dust from a larger ring that is on the border of its orbit.
Done, saved you a long and pointless naritive.
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Wikipedia: [Cassini] correctly deduced that Iapetus is locked in synchronous rotation about Saturn and that one side of Iapetus is darker than the other
Medium: Iapetus, presented a tremendous mystery to Cassini.
Re:To summarize. (Score:5, Informative)
I found this article to be rather long winded in order to create a story with suspense. The moon has a side facing away from Saturn which is darker then the side facing saturn. It seems to be due to collecting dust from a larger ring that is on the border of its orbit.
Done, saved you a long and pointless naritive.
Actually, that's not quite correct. You've got two errors there, and missing the real mystery, although the article itself actually fails to explicitly specify what the solution is.
The darker side is actually the leading hemisphere, not the far or outer side (from Saturn). Dust doesn't onto the far side, the moon plows through it in places, getting dust on the leading side. No mystery here for quite a while though - telescopes have been able to make out "the dark patterns look a lot like dust" for quite a while. The Phoebe ring itself was only detected about 10 years ago, but it was expected that dust was coming from the outer moons for a while.
The thing is, if the only process happening was that dust was being swept up by Iapetus, then every time the dark side faced the Sun, the dark coating would heat up, cause the ice underneath it to sublime (think evaporate, if that doesn't mean anything - it's close enough) and freeze again over the dust, leaving behind a light surface again. But we see a dark surface. Why? Mystery!
The solution (which the article doesn't really explain fully) is that initially dust from the ring caused ice to turn to gas, leaving behind a dark residue that we now see (and the Cassini probe has been able to measure), but instead of just floating around above the (relatively) warm, dark surface until it faces away from the Sun and cools down, much of the vapour refreezes on the light side as it passes over it due to the lower temperature there.
The dark residue (not the original dust) now causes further heating each orbit, repeating the cycle. Over time, a large amount of ice from the leading side is being evaporated away, leaving that side to get darker and darker from the residue, with a certain amount of the ice migrating to the light side and refreezing (as light coloured ice) keeping it nice and bright.
TLDR: Mystery! Dust doesn't explain the dark leading side of Iapetus! Ice would cover it in a shiny coat each orbit. Planetary detectives trace the culprit to dark residues left behind as heated ice moves to a new neighbourhood on the cooler side of the moon. More dark areas means more solar heating, and more ice migrating away in a self-perpetuating cycle. Mystery solved! Good job, planetary scientists!
Re:To summarize the summary (Score:2)
This!
By all means ignore the GP post and RTFA. Lots of cool pictures and chat about how Phoebe is special and how ridges from old impact craters on Iapetus are really old.
Unless you're not all that into space stuff... then I'd understand if you might find TFA "long-winded" and would probably appreciate having more time for reading buzzfeed "articles".
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Interplanetary redlining and white flight! Bad job, scientists!
Re:To summarize. (Score:5, Funny)
Where were you for all those Bennett Hassleton articles?
Re: To summarize. (Score:4, Insightful)
Derp!
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Wow, yeah science should never attempt to be interesting, especially for the lay audience. All of the longstanding questions, brilliant technological achievements, and research built on the shoulders of giants is completely worthless to talk about when all the had to tell us is "there's moving dust on it".
In other news I wasted a whole 8 seconds reading that first sentence describing your unnecessary editorial opinion and post script. Your summary was twice as long as it needed to be.
Seriously, 10 short lar
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The moon has a side facing away from Saturn which is darker then the side facing saturn. It seems to be due to collecting dust from a larger ring that is on the border of its orbit.
You said that very succinctly. Unfortunately it is also very wrong.
Read TFA again. The dark side (of Iapetus-- not the Force) is the side that is facing forward in its orbit.
May the Farce be with you.
Re:Iapetus... (Score:5, Interesting)
The fun is that in 2001, the bright side of Iapetus was sculpted, with the monolith in the middle. In reality the dark side is sculpted from passage through the dust ring.
Kubrick switched to Jupiter due to F/X ease (Score:3)
Somebody has to say it... (Score:1)
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right it is a egg, of a space dinosaur.
that is why it has a ridge.
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What a hideous annoying website medium.com is (Score:5, Insightful)
We aren't all using tablets or phones. Looks like crap on my laptop.
As for the article, if you are going to casually use words like "sublimate" without definition, it means your target audience is sophisticated enough that you don't need to write using a breathless, made for reality TV, annoyingly *excited* tone.
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Pretty safe to assume that most people who were capable of reading the first clause of that sentence could also read the second clause and understood the point he was making.
...it means your target audience is sophisticated enough that you don't need to write using a breathless, made for reality TV, annoyingly *excited* tone.
The Ridge (Score:5, Interesting)
POssibly the moon is formed from 2 bodies colliding and before it could completely settle down into a round shape it froze with that ridge remaining?
Nope (Score:2)
POssibly the moon is formed from 2 bodies colliding and before it could completely settle down into a round shape it froze with that ridge remaining?
Nah, it's clearly an equatorial mass driver that was covered over with rock to keep it safe from meteorites.
mindblowing (Score:5, Funny)
Dude... Do you think that when Pink Floyd sang about the Dark side of the moon, they were really talking about Iapetus?
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I don't know, but I heard that all of Bennett Haselton's submissions sync up with it.
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yay hype (Score:1)
and unreadable hipster websites
The Strangest Moon (Score:1)
was Kieth.
You Can't HANDLE The Truth (Score:2, Funny)
It amazes me that so many allegedly "educated" people have fallen so quickly and so hard for a fraudulent fabrication of such laughable proportions. The very idea that a gigantic ball of rock happens to orbit our planet, showing itself in neat, four-week cycles -- with the same side facing us all the time -- is ludicrous. Furthermore, it is an insult to common sense and a damnable affront to intellectual honesty and integrity. That people actually believe it is evidence that the liberals have wrested the la
Equatorial Ridge (Score:2)
My armchair theory for the ridge would be it wasn't always tidally locked, and plowed through a significant amount of debris material along that plane originally. Eventually becoming tidally locked, and the larger particulate had been mostly thinned out. And the tilt happening as the rotation failed, much like a top wobbles and falls over after losing momentum.
Grammar (Score:1)
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Even the NASA does not agree with you "A solar system refers to a star and all the objects that travel in orbit around it. ..."
https://solarsystem.nasa.gov/p... [nasa.gov]
If one day humans reach other solar or if you prefer star systems, then they likely will keep using the terms solar and sun to refer to their local star. A solar panel will never be renamed to something like an Alpha Canis Minoris panel.