Hyper-Earths

[Green Baron]

6 hours ago, Racescort666 said:

Please excuse my ignorance on this but how do planets achieve such high densities? *snip*

In case of the link above it is assumed to be the nucleus of a former white dwarf. The formerly binary system consisted for a while as a fast rotating neutron star that stripped the atmosphere from its companion, the mentioned white dwarf.

It is assumed that the white dwarf's orbit partially took place below the roche limit, so that the volatile parts were absorbed by the neutron star. The solid, dense carbon (diamond ;-)) core of the white dwarf stayed intact and now orbits very close to the neutron star; it has, so the conclusion, converted into a planet.

Was that more or less correct ? I haven't read through the whole article because there's a lot of math in it and that takes too much time for me to understand.

[YNM]

13 hours ago, ProtoJeb21 said:

It's possible they may act like stellar remnants, but there's nothing better to classify them. They're too large to be white dwarfs or neutron stars (radius-wise), too small to be brown dwarfs, and too dense to be gas planets. As insert_name suggested, several of them, including Tartarus and Thanatos, are likely Chthonian planets that were once gas giants with large cores.

 

9 hours ago, Racescort666 said:

Please excuse my ignorance on this but how do planets achieve such high densities? Is it like how neutron stars are basically star sized atomic neuclei? If the surface has iron and tungsten on it wouldn't the density of the surface materials be 7.8 g/cc and 19.2 g/cc respectively but that is less than the densities discussed? Am I thinking about it wrong because these are their densities at STP and they have different densities and/or assume different forms at absurd pressures like those found at the core of a gas giant? How do they keep those densities and forms with the lighter gas blown away?

Well I think that these might be leftover cores of brown dwarfs or something. I'm not really sure but as the materials that forms planets and stars are almost the same, just that one sticks gasses better and the other doesn't, maybe some brown dwarf actually is close in structure to a gas giant, and actually have rocky cores. To a good extent, brown dwarf materials are in a state of degeneracy, one or the other. Maybe if we found such objects on the scale of a few Mjup, they might actually have been a white dwarf instead. For a lot of reasons it'd be really undermining to call them "planets".

Pre-review/publication version of the paper linked above, courtesy of arXiv : https://arxiv.org/pdf/1108.5201

To the question of how do they exist...

... well.

Edited August 10, 2017 by YNM

[ProtoJeb21]

On 8/10/2017 at 0:31 AM, YNM said:

 

Well I think that these might be leftover cores of brown dwarfs or something. I'm not really sure but as the materials that forms planets and stars are almost the same, just that one sticks gasses better and the other doesn't, maybe some brown dwarf actually is close in structure to a gas giant, and actually have rocky cores. To a good extent, brown dwarf materials are in a state of degeneracy, one or the other. Maybe if we found such objects on the scale of a few Mjup, they might actually have been a white dwarf instead. For a lot of reasons it'd be really undermining to call them "planets".

Pre-review/publication version of the paper linked above, courtesy of arXiv : https://arxiv.org/pdf/1108.5201

To the question of how do they exist...

... well.

J1719b is most definitely the remains of a stellar remnant....so basically a stellar remnant remnant. I'm also favoring the evaporated brown dwarf/gas giant hypothesis explanation for Tartarus and Thanatos. However, planets like JS 183b and K2-77b are farther from their stars and unlikely to be stellar or planetary remnants. I think they might have formed naturally, due to their host stars' INCREDIBLY high metal content. Maybe frequent mergers with massive planets also helped. But Morsaption is still unexplained, though.

[YNM]

2 hours ago, ProtoJeb21 said:

J1719b is most definitely the remains of a stellar remnant....so basically a stellar remnant remnant. I'm also favoring the evaporated brown dwarf/gas giant hypothesis explanation for Tartarus and Thanatos. However, planets like JS 183b and K2-77b are farther from their stars and unlikely to be stellar or planetary remnants. I think they might have formed naturally, due to their host stars' INCREDIBLY high metal content. Maybe frequent mergers with massive planets also helped. But Morsaption is still unexplained, though.

IMO JS 183b might be a flung-away puff planet, or it might have been hit by some flares. K2-77b might have migrated off. Morsaption... well, maybe that is within the definition of a remnant-remnant. I have no idea of what the progenitor was but the system must have undergo some dramatic phases in it's life.

Edited August 11, 2017 by YNM

[ProtoJeb21]

Bad news: it turns out Tartarus is a false positive caused by stellar noise. However, there is a potential new Hyper-Earth candidate. 

The star EPIC 203533312 is a large F-type star around twice the Sun's radius with a temperature over 7,000 Kelvin. Only a few days after the discovery of Thanatos, I found out that this star had a known planet candidate...in a VERY horrific orbit. This abomination, nicknamed Kraken, has an orbit lasting every FOUR HOURS and experiences temperatures in excess of 8,800*F - as hot as a late G dwarf. However, there is one problem: at that close-in, Kraken should be INSIDE its host star. This means two things: either the star is significantly smaller than expected (considering how large the error range is for its mass and radius), or Kraken is an eclipsing binary with an 8.4-hour orbit. The latter seems more likely, but stars that big and that close are incredibly dangerous. It's possible that the two of them could be what's called a Contact Binary, where material from the two close stars touch each other, making the system look somewhat like a peanut with a thin middle section. This system could be very close to merging and creating a Red Nova, potentially within the next several thousand years. 

[ProtoJeb21]

A new Hyper-Earth!

My brain is slowly dying from the shock of this thing!

Halp

[ProtoJeb21]

I've added several planets to the Mega Earth page on Wikipedia, including a few planets I would classify as Hyper-Earths:

https://en.wikipedia.org/wiki/Mega-Earth