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beecee

Planetary Migration:

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In reference to the following article and paper at https://phys.org/news/2019-05-rare-earth-metals-atmosphere-glowing-hot-exoplanet.html and the paper at https://arxiv.org/abs/1905.02096v1

With regard to the extract in the article thus, "Therefore, its atmosphere reaches temperatures of around 4000 °C. In such heat, all elements are almost completely vaporized and molecules are broken apart into their constituent atoms" I find it rather difficult to imagine how any planet could form that close to its parent star and at such temperatures. Is this evidence for "planetary migration"? I also vaguely remember a proposition a few years ago, supporting the "planetary migration" hypothesis with our own gaseous giants, Jupiter and Saturn...something along the lines of probably forming much further out then their current orbital parameters, migrating inwards, then back again to their now apparent stable orbits.

Any thoughts?

Edited by beecee

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Planetary migration is, by now, pretty well established. This applies, as you suggest, to the movement of the gas/ice giants in our system. (IIRC one giant was likely expelled from the early system.) I have several papers on the subject and will look for the most recent/relevant and post links, likely tomorrow.

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24 minutes ago, Intrigued said:

Planetary migration is, by now, pretty well established. This applies, as you suggest, to the movement of the gas/ice giants in our system. (IIRC one giant was likely expelled from the early system.) I have several papers on the subject and will look for the most recent/relevant and post links, likely tomorrow.

Thanks.

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1 hour ago, beecee said:

Thanks.

What happens in the core of such a planet? Jupiter with it's atmosphere at 4000c can this cause fusion in the core?  

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1 minute ago, Moontanman said:

What happens in the core of such a planet? Jupiter with it's atmosphere at 4000c can this cause fusion in the core?  

Depends on mass afaik....with Jupiter it is thought that at the core, metallic hydrogen may exist, or at least take on similar metallic properties. The next step up, again depending on mass, is the Brown Dwarf stage where possible limited core fusion may take place.... 

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1 minute ago, beecee said:

Depends on mass afaik....with Jupiter it is thought that at the core, metallic hydrogen may exist, or at least take on similar metallic properties. The next step up, again depending on mass, is the Brown Dwarf stage where possible limited core fusion may take place.... 

if I under stood it correctly deuterium/He3 fusion has already occured in Jupiter and is over but how hot would it get that near a star?  

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I found this which seems to support what I said.....https://en.wikipedia.org/wiki/Brown_dwarf

extract:

"Below this range are the sub-brown dwarfs (sometimes referred to as rogue planets), and above it are the lightest red dwarfs (M9 V). Brown dwarfs may be fully convective, with no layers or chemical differentiation by depth.[3]

Unlike the stars in the main sequence, brown dwarfs are not massive enough to sustain nuclear fusion of ordinary hydrogen (1H) to helium in their cores. They are, however, thought to fuse deuterium (2H) and to fuse lithium (7Li) if their mass is above a debated[4] threshold of 13 MJand 65 MJ, respectively.[2] It is also debated whether brown dwarfs would be better defined by their formation processes rather than by their supposed nuclear fusion reactions."

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1 minute ago, beecee said:

I found this which seems to support what I said.....https://en.wikipedia.org/wiki/Brown_dwarf

extract:

"Below this range are the sub-brown dwarfs (sometimes referred to as rogue planets), and above it are the lightest red dwarfs (M9 V). Brown dwarfs may be fully convective, with no layers or chemical differentiation by depth.[3]

Unlike the stars in the main sequence, brown dwarfs are not massive enough to sustain nuclear fusion of ordinary hydrogen (1H) to helium in their cores. They are, however, thought to fuse deuterium (2H) and to fuse lithium (7Li) if their mass is above a debated[4] threshold of 13 MJand 65 MJ, respectively.[2] It is also debated whether brown dwarfs would be better defined by their formation processes rather than by their supposed nuclear fusion reactions."

I understand that but would extreme proximiy to it's parent star cause a Jupiter mass object to undergo fusion? 

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1 minute ago, Moontanman said:

I understand that but would extreme proximiy to it's parent star cause a Jupiter mass object to undergo fusion? 

OK, good question...If it did I would say it would be classified as a sub Brown Dwarf? Just a guess though on my part, someone more attuned to these classifications from rocky planet to gaseous planet, to brown dwarf to star may shed more light.

Actually your previous post re deuterium fusion in Jupiter is something I have not heard of.

 

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Here is another article on this concept of Planetary Migration...                              https://phys.org/news/2019-05-gravitational-protoplanetary-disks-super-earths-stars.html

Gravitational forces in protoplanetary disks may push super-Earths close to their stars:

The galaxy is littered with planetary systems vastly different from ours. In the solar system, the planet closest to the Sun—Mercury, with an orbit of 88 days—is also the smallest. But NASA's Kepler spacecraft has discovered thousands of systems full of very large planets—called super-Earths—in very small orbits that zip around their host star several times every 10 days.

Now, researchers may have a better understanding how such planets formed.

A team of Penn State-led astronomers found that as planets form out of the chaotic churn of gravitational, hydrodynamic—or, drag—and magnetic forces and collisions within the dusty, gaseous protoplanetary disk that surrounds a star as a planetary system starts to form, the orbits of these planets eventually get in synch, causing them to slide—follow the leader-style—toward the star. The team's computer simulations result in planetary systems with properties that match up with those of actual planetary systems observed by the Kepler space telescope of solar systems. Both simulations and observations show large, rocky super-Earths orbiting very close to their host stars, according to Daniel Carrera, assistant research professor of astronomy at Penn State's Eberly College of Science.

more at link......

the paper:

https://academic.oup.com/mnras/article-abstract/486/3/3874/5432363?redirectedFrom=fulltext

Formation of short-period planets by disc migration:

ABSTRACT:

Protoplanetary discs are thought to be truncated at orbital periods of around 10 d. Therefore, the origin of rocky short-period planets with P < 10 d is a puzzle. We propose that many of these planets may form through the Type-I migration of planets locked into a chain of mutual mean motion resonances. We ran N-body simulations of planetary embryos embedded in a protoplanetary disc. The embryos experienced gravitational scatterings, collisions, disc torques, and dampening of orbital eccentricity and inclination. We then modelled Kepler observations of these planets using a forward model of both the transit probability and the detection efficiency of the Kepler pipeline. We found that planets become locked into long chains of mean motion resonances that migrate in unison. When the chain reaches the edge of the disc, the inner planets are pushed past the edge due to the disc torques acting on the planets farther out in the chain. Our simulated systems successfully reproduce the observed period distribution of short-period Kepler planets between 1 and 2 R⊕. However, we obtain fewer closely packed short-period planets than in the Kepler sample. Our results provide valuable insight into the planet formation process, and suggests that resonance locks, migration, and dynamical instabilities play important roles in the formation and evolution of close-in small exoplanets.

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On 5/10/2019 at 8:35 PM, Moontanman said:

I understand that but would extreme proximiy to it's parent star cause a Jupiter mass object to undergo fusion

According to this link it would take an object 13 times the mass of Jupiter to fuse deuterium. I might have read it many years ago before these things were completely figured out or I misread it... 

https://phys.org/news/2014-02-jupiter-star.html

 

Quote

There's another object that's less massive than a red dwarf, but it's still sort of star like: a brown dwarf. This is an object which isn't massive enough to ignite in true fusion, but it's still massive enough that deuterium, a variant of hydrogen, will fuse. You can get a brown dwarf with only 13 times the mass of Jupiter. Now that's not so hard, right? Find 13 more Jupiters, crash them into the planet?

I have been following Issac Arthur and have talked about how an artificial star might be made using pure deuterium or He3, so far no resolution... 

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