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Thread: Neutron star merger question

  1. #1
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    Neutron star merger question

    I am a little confused. From what I have read here and online I was under the impression that we have already in the past seen the merge of 2 neutron stars but is the article below if makes it seems and though we have detected this this month for the first time ever.

    My question is have 2 neutron stars as the mentioned ever merged in the past or is this the first time it happens?

    https://www.google.ca/amp/s/phys.org...-telescope.amp

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    Well if I'm reading the table correctly in the Wikipedia article, then 2017 saw the first Neutron Star merger detected by LIGO and VIRGO (link to specific GW event article).

    https://en.wikipedia.org/wiki/List_o...e_observations

    There have been several neutron star mergers since.

    What makes you wonder if these NS mergers were a new type of GW event? The article doesn't say anything about it. It does say these neutron stars may be of a "potentially a new class of neutron star object".

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    Sorry that’s what I meant, it’s a new event that never happened. So what makes this new since universe has been around for 13.8 billion years. What is different about this,

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    Quote Originally Posted by Sinbad View Post
    Sorry thatís what I meant, itís a new event that never happened. So what makes this new since universe has been around for 13.8 billion years. What is different about this,
    Gravitational waves were predicted by Einstein but never observed until 2015. So these events have probably been occurring for billions of years but we just now have the instruments to observe the ripples in spacetime.

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    Does this not mean what I said potentially a new class of neutron star object".

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    Quote Originally Posted by Sinbad View Post
    I am a little confused. From what I have read here and online I was under the impression that we have already in the past seen the merge of 2 neutron stars but is the article below if makes it seems and though we have detected this this month for the first time ever.

    My question is have 2 neutron stars as the mentioned ever merged in the past or is this the first time it happens?

    https://www.google.ca/amp/s/phys.org...-telescope.amp
    The "a neutron star collision" in the article is the first detection of gravitational waves from merging neutron stars in 2017 by LIGO and Virgo. Then there is "In the past three weeks, another detection has been announced, with signals seeming to suggest a merger of two unexpectedly massive neutron starsópotentially a new class of neutron star object." which is the second neutron star merger detection by just the LIGO Livingstone detector (the other detector was offline and the signal was too weak for Virgo).

    Neutron star merger has another possible merger associated with a gamma-ray burst event.

    The second gravitational wave merger is interesting. We did not detect any gamma-ray signal from it when we did from the first. The total mass exceeds that of known galactic neutron star binaries at 3.4 solar masses. Neutron star mergers are thought to first form a massive neutron star which undergoes collapse and fusion to release gamma rays. Then a black hole is formed. It is possible that this merger went directly to a black hole.
    Did LIGO Just Discover Two Fundamentally Different Types Of Neutron Star Mergers?

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    So this is something new that never happened before. How far is this from earth?

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    Quote Originally Posted by Sinbad View Post
    So this is something new that never happened before. How far is this from earth?
    Something we haven't observed before. Doesn't mean it hasn't happened before... We've been successfully looking for gravitational waves for just a few years.
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    Ok how many light years from earth is this

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    Quote Originally Posted by Sinbad View Post
    So this is something new that never happened before. How far is this from earth?
    The detection is not new. Whether this is a new class of event is still not clear. If this is the first detection of a new class of event then that event has happened many times before.
    Did LIGO Just Discover Two Fundamentally Different Types Of Neutron Star Mergers?
    The first neutron star-neutron star merger had a slew of fascinating properties, but one thing that stands out is how remarkably close it was: just 130 million light-years away, close to the limits of what the LIGO detectors could see prior to the upgrade. The second such neutron star-neutron star merger event, seen less than 4 weeks after the start of the third data-taking run, was approximately four times as distant, occurring an estimated 518 million light-years away. The signal was too distant and faint to be seen by the Virgo detector, and just by chance only one of the LIGO detectors was operational at the time.

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    So is this a new event in the universe or a. Regular event that we just saw for the first time

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    It is definitely not a "new" event because we have seen a neutron star merger before. It may be a new class of event (neutron stars merging directly to a black hole) but the evidence is not clear. It this is a new class of event then it has happened before and we are just seeing it for the first time.

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    Quote Originally Posted by Sinbad View Post
    So is this a new event in the universe or a. Regular event that we just saw for the first time
    I suspect that this event is something much smaller like a large asteroid hitting neutron star or black hole a few thousand light years from here. The fact that the signal settled in 14 milliseconds says that this must be a physically small event that resolved quickly. This sort of thing might happens a few times per decade in our galaxy.
    Forming opinions as we speak

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    Not sure what you mean by small event that has happened. You see I am not sure what any of they are trying to say means. My understanding is that this is a extremely powerful event that they have detected that never happened before and formed something they have never seen before
    Last edited by Sinbad; 2020-Jan-16 at 12:53 AM.

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    Quote Originally Posted by Sinbad View Post
    Not sure what you mean by small event that has happened. You see I am not sure what any of they are trying to say means. My understanding is that this is a extremely powerful event that they have detected that never happened before and formed something they have never seen before
    GW S200114f is an event that was observed yesterday. It lasted 14 milliseconds and did not have the usual ringing before the chirp. If you follow the link at the beginning of this post, you can see the public data about it. You can also look up a nice short summary in wikipedia. This event is very powerful by terrestrial standards, but compared to other Gravitational Wave events is likely very tiny, and only observed by us because it was close (in our galaxy instead of billions of light years away). We have never previously seen this type of GW event, but that's because we've only been looking for about 3 years. That doesn't make it rare. So far that means about 1% of events we see are this type, and 2% are neutron star-neutron star mergers. Nothing written about this event says that it must be as large or larger than other GW events. I'm not sure where you got that impression. At the moment, the equipment is not great for getting details. I understand that in five years or so, we will have an upgrade that will let us see more detail, and detect smaller and more distant events. AT the moment, when an event is detected an alert goes out and various systems look for other evidence of transients (Gamma Ray Bursts, XRay flares, optical wavelength brightenings, neutrinos, etc) Usually these come up empty, but when something is spotted, it tells us new precious details. We are still at the beginning of learning how to observe these things.
    Forming opinions as we speak

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    Quote Originally Posted by Sinbad View Post
    So this is something new that never happened before. How far is this from earth?
    Again, you're worrying yourself about something that is nothing to worry about. Neutron star mergers have definitely happened many times in the past, but we didn't have instruments to look at them. In fact, it is believed that neutron star mergers, along with supernova explosions, are partly responsible for our existence, as they created the elements heavier than iron.
    As above, so below

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    Quote Originally Posted by Sinbad View Post
    Ok how many light years from earth is this
    About 140 million light years. So very, very far away.
    As above, so below

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    GW19042 is the event I was referring to fro January 6

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    GW19042 is the event I was referring to fro January 6

    https://www.ligo.org/detections/GW190425.php

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    GW19042 is the event I was referring to fro January 6

    https://www.ligo.org/detections/GW190425.php

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    Quote Originally Posted by Sinbad View Post
    GW19042 is the event I was referring to fro January 6

    https://www.ligo.org/detections/GW190425.php
    The fact sheet from that page says the event was 287 to 744 million light-years away.

    https://dcc.ligo.org/public/0165/G20..._Factsheet.pdf

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    I understand but my question was this one and the one from January 6 we’re said to be completely different. My questions is what makes them difference and also the one from January 6 was very powerful the article said. Is that the most powerful ever or just more powerful that the April events.

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    Quote Originally Posted by Jens View Post
    Again, you're worrying yourself about something that is nothing to worry about. Neutron star mergers have definitely happened many times in the past, but we didn't have instruments to look at them.
    We had the instruments. Eyes.
    In the previous millennium, we saw 3 white dwarf mergers/type I supernovae. SN 1006 Lupi, magnitude -7,5, SN 1572 Cassiopeiae, magnitude -4, SN 1604 Ophiuchi, magnitude -3.
    What is the ratio of frequency of neutron star mergers/kilonovae to white dwarf mergers/type I supernovae? For the statistical guess of 30 type I supernovae within 10 000 lightyears of Sun within last 10 000 years, how many kilonovae should have happened in the same region?
    How bright would a kilonova at 10 000 lightyears be?

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    I apologize if I sound stupid with my comments. I just do not understand the lingo and am trying to. The way I read the article is that something happened that has never happened before. I am probably wrong that’s why I am here lol

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    Quote Originally Posted by Sinbad View Post
    I apologize if I sound stupid with my comments. I just do not understand the lingo and am trying to. The way I read the article is that something happened that has never happened before. I am probably wrong that’s why I am here lol
    I think you are falling into a booby trap created by one of my pet peeves, which is saying "new type of object or event" when they mean "newly discovered or observed type of object or event." What never happened before is having instruments capable of observing these events. Our best theory now is that much of the gold on Planet Earth was produced by neutron star mergers right here in this galaxy billions of years ago.

    While I am at it, let's make some analogies. The event antoniseb is interpreting as a relatively small and nearby event could be analogous to hearing a firecracker across the street. The one that appears to be a superheavyweight neutron star merger at a vast distance could be analogous to hearing a large naval gun that is fired 20 miles away. I have heard both and they are distinctly different.
    Last edited by Hornblower; 2020-Jan-16 at 04:21 PM.

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    Quote Originally Posted by Hornblower View Post
    I think you are falling into a booby trap created by one of my pet peeves, which is saying "new type of object or event" when they mean "newly discovered or observed type of object or event." What never happened before is having instruments capable of observing these events.
    I repeat, we always had eyes.
    And a small correction: of the white dwarf mergers, SN1885, in Andromeda, at +5,9, also could be called "seen".

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    Thank you all

  28. #28
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    Quote Originally Posted by chornedsnorkack View Post
    I repeat, we always had eyes.
    And a small correction: of the white dwarf mergers, SN1885, in Andromeda, at +5,9, also could be called "seen".
    I was referring to detection of gravitational waves from these merger events.

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