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Gnargenox
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06 Sep 2018 06:32

In our conversation that's the one thing he got excited about. I'm not even sure what's possible so I can only assume he's learning about it also as he's reading it off.

That's what led us to the assumption it was a supernova Survivor
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06 Sep 2018 07:12

Gnargenox wrote:
Source of the post I found this (from June) fairly easily though and the numbers are extremely similar.
http://adsabs.harvard.edu/abs/2018ATsir1642....1R

According to this source, the planet has 0.39 solar masses, so it's a pretty heavy thing!
 
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06 Sep 2018 14:43

Gnargenox wrote:
Source of the post In our conversation that's the one thing he got excited about. I'm not even sure what's possible so I can only assume he's learning about it also as he's reading it off.

Well, general relativity for this situation can account for about 0.1 arcseconds per orbit.  Things like tidal dissipation, frame dragging, etc can modify that slightly, but 44 degrees per orbit is, um, nuts.  That would require a very close orbit around a black hole... (and being close enough to a stellar mass black hole to get that much precession would instantly destroy the planet).

A supernova survivor can perhaps explain the eccentricity of the planet, by the direct kick and especially the mass loss of the star.  But I don't think it explains the orbital precession.
 
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06 Sep 2018 16:05

Yes I would quickly agree without even doing any math but I wonder perhaps if it's a football shape, if that makes any difference.
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Watsisname
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06 Sep 2018 16:32

6 orders of magnitude difference?  Besides, why would it be a football shape?  Tidal distortion is pretty small for that kind of orbit around a neutron star, and 0.5 Earth masses is enough to be spherical.
 
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06 Sep 2018 16:46

I'm figuring a perihelion of 0.336 & Aphelion of 16.464 with an aspect ratio of 0.28 A pretty thin sliver. I have no idea of the solar mass for the pulsar, but they are pretty dense, about a billion tons a teaspoon. Whip it! Whip it real good!

Formula for Precession - (Torque-induced - Classical Newtonian) is
 ω p = m · g · r over I s · ω s

The angular velocity of precession (deg/s)
=
mass in kg (3e+24) *  9.80665 m/s^2  * r (unknown)
over
moment of inertia (kg*m^2) * angular velocity of spin about the spin axis (unknown)

I'm stalled out now. But, if it is spinning fast enough....
Anyway, that paper I provided a link to is the same exoplanet he was discussing with me.

I think it will be made public at the iau 2018 conference.
https://astronomy2018.univie.ac.at/post ... cts-sorted
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Watsisname
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06 Sep 2018 17:01

Gnargenox wrote:
Source of the post I'm figuring a perihelion of 0.336 & Aphelion of 16.464 with an aspect ratio of 0.28 A pretty thin sliver.

Those numbers look good. :)   And here's an orbital plot:

Image

(Of course, what is being claimed is that the orbit actually looks like this.)

Gnargenox wrote:
Source of the post I have no idea of the solar mass for the pulsar, but they are pretty dense, about a billion tons a teaspoon.


The mass of a pulsar (or neutron star in general) is usually between about 1.4 and 3 solar masses.  If the orbital period is 20.2 years with semimajor axis of 8.4AU, this means the pulsar mass must be about 1.45 solar masses (by Kepler's Third Law).


Gnargenox wrote:
Source of the post I think it will be made public at the iau 2018 conference.

There we go!  Found it near the bottom of the page:

The planet of the pulsar B0525+21 has orbital period P2 = 20.2 yr, orbital semi-major axis a2 = 8.4 AU, eccentricity e2 = 0.96, and mass m2sini = 0.5M⊕. Additionally, the precession of the planet's line of apses has been measured, and it is dφ = -0.77 rad/period. A high eccentricity may indicate that this planet has survived a supernova explosion.
 
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06 Sep 2018 17:25

Awesome. I didn't get an F minus! :)
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06 Sep 2018 17:37

I'm pretty sure you only get an "F" if you fail something, Gnargenox. I should know  :?.

BTW, awesome news find! Just goes to show you can find planets anywhere.
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06 Sep 2018 18:20

Yeah, sorry for focusing so hard on the precession -- I'm just really curious and confused about it.  I tried applying formulas from this paper for the spin-induced quadrupole moment effect on apsidal precession, but even with absurdly fast spin rates (or greatly distorted shape) on the companion I still come up with something less than an arcsecond per orbit.  

So I'm not sure if we're misunderstanding what -0.77rad/period means, or if it's just mis-stated in the abstract, or if there is some other (enormous) effect going on that I'm not considering.  Probably there is simply supposed to be a "micro" in front of radians.  But anyway, at the very least, a possible supernova survivor planet is extremely interesting.  I look forward to the paper. :)
 
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06 Sep 2018 20:00

One last quick thought: It was a super Earth with a very very short orbital period and semi-major axis that got blown in half and has been yo-yoing for millions of years since, without any other planetary object to perturb it?
I can't wait to learn more too. Only a half dozen Pulsar planets have been found.
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06 Sep 2018 21:09

Watsisname wrote:
Source of the post and 0.5 Earth masses is enough to be spherical.

As I said here,
JackDole wrote:
Source of the post According to this source, the planet has 0.39 solar masses, so it's a pretty heavy thing!

according to the source named by Gnargenox, the mass of the planet is 0.39 solar masses, not 0.5 Earth masses.
The mass of the neutron star in SE is 2.5. But that can not be right, because the maximum mass of a neutron star is 2.16 solar masses. As far as I know.

Here's the orbit in SpaceEngine. The data are from the article mentioned by Gnargenox.
scr00061.jpg
 
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06 Sep 2018 21:37

I believe you'll notice in the two different sources there's conflicting data, since revised and most likely will be revised again before going public.
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07 Sep 2018 00:05

Yeah, there are two sources with conflicting data.  Or rather, what appear to be different fits or interpretations of the data.  The properties of the planet (or whatever it is) are inferred from timing variations in the pulsar.

JackDole wrote:
Source of the post The mass of the neutron star in SE is 2.5. But that can not be right, because the maximum mass of a neutron star is 2.16 solar masses. As far as I know.

The limit for cold non-rotating neutron star is 2.16 solar masses, but they can be a bit heavier with spin.  2.5 solar masses could be possible.  But in this case, if the reported planet mass is 0.5 Earth masses (from the IAU conference page), and the orbital period is 20.2 years with 8.4AU semimajor axis, then the mass has to be 1.45 solar masses (with whatever error bars, since there are no uncertainties for these figures.)

Alternatively, (using the data here), if the "planet" mass is 0.39 solar masses with 10.35AU semimajor axis and 27.74 year period, then the neutron star must be 1.06 solar masses, which is rather on the light side for a neutron star.

It would be best to wait for the presentation and paper to be released.
 
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07 Sep 2018 03:02

Watsisname wrote:
Source of the post The limit for cold non-rotating neutron star is 2.16 solar masses,

Why is this differentiation made, rotating and non-rotating neutron stars? There are almost certainly no non-rotating neutron stars in the universe!
A nonrotating neutron star would mean a nonrotating progenitor star. But that is impossible if I have understood the mechanics of star formation correctly. Of course I'm just a layman.


By the way, not rotating black holes should also be rare. But they could theoretically result when two counter-rotating black holes merge. However, they would have to rotate at the same speed.

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