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Stargazing When Neutron Remnants Collide

  1. Oct 19, 2017 #1
    Okay, as we all know, there's been a lot going on in the world of Astronomy and Astrophysics recently due to the collision of two Neutron Remnants. Personally refuse to call them "stars", because they are the remnants of proper stars and not proper stars in and of themselves. There have even been several various topics posed here in the PF revolving around the incident. Yet in all of this no one, from what I've seen, has taken any kind of stand on just what the results of this collision will be.

    Now I'm no expert by any means, but here's what I've found so far in my research into this. Please feel free to correct any incorrect aspects. The point here is to get a discussion going on just where the NGC4993 neutron remnant collision is going, not to say I'm smarter than anyone else.

    1. Neutron Remnants are created by supernovas that produce a neutron remnant that is 1.1 - 3.0 solar masses in size. (I've seen estimates from 1.1-2.0 and 1.5-3.0 so I'm just using the upper/lower ends).

    2. The Neutron Remnants in question were estimated at 1.1 and 1.6 solar masses each. Total = 2.7

    3. when they reached a certain point in their relative closeness and speed, they would have been a bulging out of material mass that should have been thrown out like a slingshot due to the orbital speed, and also mass thrown out from the sheer force of the impacting explosion.

    4. Even though they would have thrown out mass, their combined size is estimated to be 2.6 solar masses? Only -0.1 from the combined pre-collision mass of the two? (I would have expected 2.1 myself).

    Now... Given that a Neutron Remnant is apparently between 1.1 and 3.0 solar masses, and the resulting collisions combined weight is 2.6 solar masses, wouldn't the combined object just be a larger neutron remnant? Like two planets colliding and forming a larger planet? Of course some material would be lost to space, but the overall planet still exists, so wouldn't the neutron remnant? However, I'm hearing people mention black holes, magnetrons, and all other kinds of possible other results from the collision that simply doesn't make sense to me since they should require much more mass.

    What are your thoughts on what the final product of this collision will be and why? IF anyone's around in another 100,000 years, we can see who was right. :)
  2. jcsd
  3. Oct 19, 2017 #2


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    A couple of comments:

    (1) I think trying to re-define an established term by getting millions of people to change their speech patterns is a waste of time. Everyone else calls them "neutron stars" and have for over 50 years.

    (2) There is a maximum mass that a neutron star can have before it collapses into a black hole, but we don't know exactly what that mass is, because we have limited knowledge of how matter behaves at these extreme densities. There is at least one known neutron star with a mass of 2.0 solar masses so the limit is greater than this. On the other hand, most experts believe that the limit ls less than 3 solar masses. So we don't really know whether this ~2.6 solar mass object that resulted from this merger is a neutron star or a black hole. David Shoemaker in the LIGO press conference made this point. In this excellent summary paper, the author makes the statement that, "The large quantity of ejecta from GW170817 suggests that a temporarily stable hypermassive NS remnant was created during the merger." So it appears that the result was a neutron star, at least temporarily.
    Last edited: Oct 19, 2017
  4. Oct 19, 2017 #3

    Vanadium 50

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    I agree. Also, "neutron remnant" isn't correct either, since these are not remnants of neutrons. I do appreciate that the OP lead off with this, because it allows people who don't want to have to put in the extra effort to communicate with a non-expert who wants to use his own names and definitions to act on this preference.
  5. Oct 19, 2017 #4


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    and also going further than what the other two responders have correctly stated........

    If you have found articles whilst doing research, it is the proper thing on PF to state the references you are alluding to
    www links to scientific papers etc, as it helps us to judge their quality and make sure we are all on the same page when discussing the topic :smile:

  6. Oct 19, 2017 #5
    Not at all. Just letting you know what I'm referring to. I don't have to agree with something just because everyone else does.
    I do like the statement on the Hypermassive NS, that makes sense.
    I apologize if my non-expert terms and/or thoughts offend. Not my intent. I just wanted the opinions on those here in the PF.... not necessarily some expert scientists opinion read in a paper somewhere.
  7. Oct 19, 2017 #6
    Apologies. Haven't had to quote sources in a few decades, and I don't think "reading here and there across the internet" qualifies. I was just wanting people opinions in PF... not some experts somewhere in a deep cavern or university somewhere.
  8. Oct 19, 2017 #7
    Perhaps I'm simply in the wrong place. I'm not a student, professor, astrophysicist, or some world class astronomer. Just a guy who loves space and the vast wonders found within it, and would love some simple conversation. Obviously, most here are simply too in-tuned to the scholastic. I do thank you, however, for seeing that I was just trying to communicate. Enjoy the forum.
  9. Oct 19, 2017 #8


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    definitely not .... but there are just guidelines to follow that make things work well for everyone :smile:
    Like using correct terms for things and if you are not sure, then ask for the correct term so we are all on the same page when discussing topics.
    Not just posting " .... I read this or I read that ...." where possible, always give some references, even if it's Wiki :wink:

    Nor am I, I have been doing amateur astronomy for 50 + years. It's a love that has never left me. I'm into all sorts of astro stuff from just plain observing through to photography and bit of low level research. Tho I have done university level studies, it wasn't in astronomy, rather it was geology, which I am also very passionate about. You will find lots of posts in the earth section of the forum with images from my digital seismograph I have at home that can record quakes world wide. You will also find lots of threads of mine and other comments in threads in the astro section.

    The forum is full of people like you and me and those right up to highly experienced professionals. We all work and mingle and learn from each other about science fields that we may not know much about.

    Don't just give up and leave, that would be a loss to the chance of expanding your horizons and interests :smile:
    and meeting up with people that can teach you lots
    I have learnt much in the many years I have been a part of this forum .... it's never a dull moment

  10. Oct 20, 2017 #9
    I agree with the OP, "neutron star" is a misnomer. Although Vanadium 50 is also correct, "remnant" is not correct either. When reading papers on the subject the most often referred label for the object was "neutron core." Astronomy is rife with misnamed objects, from "planetary nebula" that has nothing to do with planets, to "quasars" because we had no clue what it was originally. We are quick to name things, even incorrectly, and slow to correct our mistakes. I do think it is important to get our terminology correct in order to avoid being misunderstood.

    The Tolman–Oppenheimer–Volkoff Limit places the upper end of a neutron degenerate core at approximately 3.0 solar masses. Similar to the Chandrasekhar Limit of ~1.44 solar masses for electron degenerate cores. However, in recent years I have been reading about "sub-Chandrasekhar" Type Ia SNe, and "super-Chandasekhar" or "superluminous" Type Ia SNe, and they have suggested that these differences may be related to how fast the object is rotating. It is therefore not unreasonable to infer that the actual limits to a particular neutron degenerate core may also vary depending upon the rate it is rotating.

    Tolman–Oppenheimer–Volkoff Limit - Wikipedia
    On Massive Neutron Cores - Physical Review, Volume 55, Issue 4, February 1939 (free preprint)
    Post-Tolman-Oppenheimer-Volkoff Formalism for Relativistic Stars - Physical Review, Volume 92, Issue 1, July 2015 (free preprint)
    Gravitational Radiation and Rotation of Accreting Neutron Stars - Astrophysical Journal Letters, Volume 501, Number 1, June 1998 (free article)
    Sub-Chandrasekhar White Dwarf Mergers as the Progenitors of Type Ia Supernovae - Astrophysical Journal Letters, Volume 722, Number 2, September 2010 (free article)
    The Type Ia Supernova SNLS-03D3bb from a super-Chandrasekhar-mass White Dwarf Star - Nature 443, July 2006 (free preprint)
    Last edited: Oct 20, 2017
  11. Oct 20, 2017 #10


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    One thing you'll find about astronomy is that, for better or worse, things are never renamed. We still use the magnitude system defined by Hipparcos over 2000 years ago. The OBAFGKM system of stellar classification is based on an initial misunderstanding, and the Population1/Population2 thing was initially misunderstood. Personally I kind of like the appreciation of the history of the discipline. But I think if you attempt to redefine an established term, you will fail.
  12. Oct 20, 2017 #11
    Well, talking about the fact that the a further understanding of things, as well as flat out corrections of totally incorrect items, led to a naming that's totally false and/or misleading isn't trying to change it... it's simply acknowledging the fact that it's wrong to begin with and why. That doesn't change the name (although in my opinion it should). So, I'm sure you have nothing to worry about.
    When I was in school (reference the classroom instructor and whatever book we used back in 1986), a Quasar was a deep space radio source that was independent of anything and everything else in the universe. Now, based on my understanding from "https://futurism.com/whats-the-difference-between-pulsars-quasars-and-magnetars/", it's been found to be nothing more than the expulsion jet of a feeding supermassive black hole that happens to be pointed towards us? What about those not pointed towards us? are they any different in any realistic way other than the direction they're pointing? Does this mean that an Omni-directional RF Transmitter is only an Omni-directional RF Transmitter IF an ONLY IF it's pointed at the receiver? What is it otherwise? Any field of thought, especially one of science where the first assumption is that everything we know is false... should be willing to update its nomenclature along with its knowledge base once an incorrect notion is proven to be something else. (note, I said "proven"... not "assumed, thought to be, theorized, or held onto because people don't want to change.... science is ALL ABOUT change).

    p.s. I hope I did that referencing correctly
  13. Oct 20, 2017 #12


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    Why does learning more about the nature of quasars necessitate changing the name? Thunder is named for the Norse god Thor, and was thought to be due to his throwing lightning bolts. Now that we know that lightning is an electrostatic discharge and thunder is the sound produced by the shock wave of superheated air, are we supposed to change the name of thunder to something else? Where do we stop?
  14. Oct 20, 2017 #13

    Vanadium 50

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    This is the part where I'm supposed to go "There, there. I didn't mean to make you feel bad. You're a special person and I like you just the way you are and your opinion is as good as anybody else's." And I'm not going to. You came here blasting with both barrels saying that you weren't an expert, but all the experts were doing it wrong, and you refuse to use standard nomenclature. OK, that's your choice. It's my choice to point out a) that';s counterproductive, and b) your proposed fix is no less wrong.

    There are plenty of cases where the name of something isn't strictly speaking accurate, but we can nevertheless communicate. Starfish are not fish. Butterflies are not flies (nor are they made of butter).
  15. Oct 20, 2017 #14
    Wow. Defensive much? I didn't say anything about anyone doing anything wrong, I simply stated my personal opinion and why so that what I was saying could be clear. I didn't once say that anyone was wrong for using the standard nomenclature.

    << Post edited by the Mentors >>
    Last edited by a moderator: Oct 21, 2017
  16. Oct 20, 2017 #15


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    Thread closed temporarily for Moderation...

    EDIT / ADD -- After some Moderation, the thread will remain closed. Thanks everybody for your contributions.
    Last edited: Oct 21, 2017
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