APOD: The Case of the Backwards Orbiting... (2018 May 30)

[neufer]

Click to play embedded YouTube video.

I think the IAU is going to have to downgrade Jupiter to a dwarf planet. Not only has it failed to clear its orbit from having lots of Greeks and Trojans, it cannot even get rid of this wanderer among the wanderers.

I like your quip, but seriously, I really think the "cleared its orbit" clause should be dumped from the list of planetary qualifiers. In the real universe can a planet ever completely clear its orbit? Aparently not, as there are areas of co-orbital stability that objects from both near and far can settle into.

Jupiter is still Master of His Domain (Monitoring Solar System "planets" is done within the confines of the honor system.)

[MarkBour]

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. BriZE - Juno's GAD-FLY

The BrEEZE upon her like a Cow in Iune,
Hoists Sail, and flies.

BrEEZE here is an Anglo-Saxon word
that was still used in Midlands dialect in Tudor times.
It refers to the GADFLIES that, in summer, trouble cows.

That's the kind of knowledge you don't get
at Oxbridge, or in a rich man's house.>>
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I find your derivation here quite interesting. 2015 BZ509 is very much a gadfly to Jupiter. But why would you go for "breeze"? Is it to relate to the BZ in the asteroid's current name? I was searching for a name that related to one that moved or bahaved in a contrary fashion to both the Greeks and Trojans, which is where I got Xanthos. If you want something close to BZ, what do you think of "Briseis"?

[neufer]

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. BriZE - Juno's GAD-FLY

The BrEEZE upon her like a Cow in Iune,
Hoists Sail, and flies.

BrEEZE here is an Anglo-Saxon word
that was still used in Midlands dialect in Tudor times.
It refers to the GADFLIES that, in summer, trouble cows.

That's the kind of knowledge you don't get
at Oxbridge, or in a rich man's house.>>
----------------------------------------------------------

I find your derivation here quite interesting. 2015 BZ509 is very much a gadfly to Jupiter.
But why would you go for "breeze"? Is it to relate to the BZ in the asteroid's current name?

I'd already heard others call BZ509 “Bee-Zee” for short
and it reminded me of Shakespeare's mention of “Breeze” in A&C.

Shakespeare's gadfly “Breeze” or “Brize” comes directly from Aeschylus's PROMETHEUS BOUND
but Stratfordians like to pretend this was a rustic Stratford word that only a small time butcher would use.

[Of course, there is also BuZZ Aldrin & Jeff BeZos.]

I was searching for a name that related to one that moved or behaved in a contrary fashion to both the Greeks and Trojans, which is where I got Xanthos.

Achilles talking horse? Diomedes's man eating horse?
https://en.wikipedia.org/wiki/Balius_and_Xanthus

If you want something close to BZ, what do you think of "Briseis"?

Helen, Cressida & Briseis would all be great names for pro-grade asteroids
that slowly amble back & forth between camps through the Lagrange L3 point:
. http://asterisk.apod.com/viewtopic.php? ... 34#p282945

But an annoying retrograde asteroid BuZZing Jupiter is best named BreeZe IMHO.

<<In medieval romances Briseis becomes Briseida. She loves and is loved by Troilus and then Diomedes. She is later confused with Chryseis and it is under variations of that name that the character is developed further, becoming Shakespeare's Cressida.>>

[MarkBour]

I was searching for a name that related to one that moved or behaved in a contrary fashion to both the Greeks and Trojans, which is where I got Xanthos.

Achilles talking horse? Diomedes's man eating horse?
https://en.wikipedia.org/wiki/Balius_and_Xanthus

Sorry, there is more ambiguity than I would have guessed. I was referring to Xanthos the god of the river Scamander, who became angry with Achilles and tried to kill him. In my copy of the Iliad, which does indeed name Achilles' horse with the same name, there is:

The eddied River broad by mortal men
Scamander call'd, but Xanthus by the Gods.

Soon as the windings of the stream they reach'd,
Deep-eddied Xanthus, progeny of Jove,

(But Wikipedia seems to prefer the spelling Xanthos to Xanthus -- https://en.wikipedia.org/wiki/Scamander)

Anyway, I guess the discoverers of 2015 BZ509 will have the privilege of naming it, eventually?

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I have a very limited understanding of planet formation. Just having learned a few bits from simplistic presentations, that would typically just say "planets form as the material in a disk clumps together". And the suggestion from that IAU definition, that planets should be clearing out their orbits. It seemed reasonable that in a given orbital band, a growing mass would perturb all the other mass in the same orbit -- pushing and pulling on the orbits of the diffuse material and causing it to either come join the larger mass or get perturbed into another orbit. But I don't put much stock in this intuition. We have a laboratory for this around Saturn, where one can see cleared bands in the rings with a single moon occupying them. Of course we have not observed for very long. But I find the stability of trojans interesting. Their pattern in this APOD reminds me of density waves elsewhere in physical phenomena. If enough mass accumulated at a Lagrange point, would that not give rise to new Lagrange-like points, stable points in an n-body system (n > 2)? For example, if enough mass is placed at L4, it should give rise to an L4' further around the circle, and no doubt other points of stability. But in the really long run, I have no idea, because it seems like I'm beginning to give a plausibility argument for spreading out around the whole ring, in contrast to what seems to be the expected trend.

[neufer]

I was searching for a name that related to one that moved or behaved in
a contrary fashion to both the Greeks and Trojans, which is where I got Xanthos.

Achilles talking horse? Diomedes's man eating horse?
https://en.wikipedia.org/wiki/Balius_and_Xanthus

Sorry, there is more ambiguity than I would have guessed. I was referring to Xanthos the god of the river Scamander, who became angry with Achilles and tried to kill him. In my copy of the Iliad, which does indeed name Achilles' horse with the same name, there is:

The eddied River broad by mortal men
Scamander call'd, but Xanthus by the Gods.

Soon as the windings of the stream they reach'd,
Deep-eddied Xanthus, progeny of Jove,

(But Wikipedia seems to prefer the spelling Xanthos to Xanthus -- https://en.wikipedia.org/wiki/Scamander)

Xanthus is generally the Latin for the Greek Xanthos.

Since the Trojan Aeneas became the original Roman,
Xanthus would also be the Trojan version.

Anyway, I guess the discoverers of 2015 BZ509 will have the privilege of naming it, eventually?

If they are 'mortal men' they would have to call it Scamander.
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If enough mass accumulated at a Lagrange point, would that not give rise to new Lagrange-like points, stable points in an n-body system (n > 2)? For example, if enough mass is placed at L4, it should give rise to an L4' further around the circle, and no doubt other points of stability.

If that much mass accumulated at L₄ there are probably no stable solutions.

[BDanielMayfield]

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A contour plot of [the effective potential for relatively slowly moving bodies] due to gravity and the centrifugal force of a two-body system in a rotating frame of reference. The arrows indicate the gradients of the potential around the five Lagrange points—downhill toward them (red) or away from them (blue). Counterintuitively, the L₄ and L₅ points are the high points of the potential. At the points themselves these forces are balanced.

I found that graphic to be fascinating Art. I've wondered about the possibilities of exoplanets forming at the L4 and L5 points of giant exoplanets. It doesn't seem to be very possible due to the potentials for objects to drift away from them.

Bruce

[MarkBour]

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A contour plot of [the effective potential for relatively slowly moving bodies] due to gravity and the centrifugal force of a two-body system in a rotating frame of reference. The arrows indicate the gradients of the potential around the five Lagrange points—downhill toward them (red) or away from them (blue). Counterintuitively, the L₄ and L₅ points are the high points of the potential. At the points themselves these forces are balanced.

I found that graphic to be fascinating Art. I've wondered about the possibilities of exoplanets forming at the L4 and L5 points of giant exoplanets. It doesn't seem to be very possible due to the potentials for objects to drift away from them.

Bruce

Ah, yes, Bruce. I had not paid enough attention to the arrows in this. So these points are not highly stable. And a large body in one of them would just change everything and make a mess, I suppose. Meanwhile, for small enough masses, they can hang out there for millions of years ... or more. I wonder if Jupiter has more or fewer trojans now than it did a billion years ago. If I follow the arrows in the diagram, then a body that is a little closer to the main planet than the point L4, for example, will be perturbed toward the planet. One that is a little farther away than L4 will be nudged further away. Where would you draw asteroid Brize in all of this? It is not in any such stable point, so it is constantly being perturbed, but it happens to have really perfect timing. There may someday be found some use for such orbits by NASA. After all, TESS is in a very creative orbit. But it would take quite a bit of energy to put something in a retrograde orbit compared to Earth.

[MarkBour]

If they are 'mortal men' they would have to call it Scamander.

Ha. Good point. But, they are not mere mortals. They are astronomers!

[BDanielMayfield]

I found that graphic to be fascinating Art. I've wondered about the possibilities of exoplanets forming at the L4 and L5 points of giant exoplanets. It doesn't seem to be very possible due to the potentials for objects to drift away from them.

Bruce

Ah, yes, Bruce. I had not paid enough attention to the arrows in this. So these points are not highly stable. And a large body in one of them would just change everything and make a mess, I suppose. Meanwhile, for small enough masses, they can hang out there for millions of years ... or more. I wonder if Jupiter has more or fewer trojans now than it did a billion years ago. If I follow the arrows in the diagram, then a body that is a little closer to the main planet than the point L4, for example, will be perturbed toward the planet. One that is a little farther away than L4 will be nudged further away.

But otoh the Jovian L4 and L5 points are stable enough for these Trojan asteroids to have been retained for 4.5 billion years! These points don't seem to be attractors, but if an object is near one and in an orbit that is sufficiently synchronized with the controlling planet it can hang out indefinitely, at least until a very unlikely encounter with another object knocks or perturbes it out of its stable orbit. The number of these objects declines very slowly nowadays, I would think.

Bruce