First Light from a Gravitational Wave Event (GW170817)

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Re: First Light from a Gravitational Wave Event (GW170817)

Post by BDanielMayfield » Thu Dec 21, 2017 10:23 pm

Thank you for sharing that Art. Never mind then. It was just Gamow gamesmanship. Proves you just can't trust them dang scientists! :lol2:
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CXC: Neutron-Star Merger Yields New Puzzle for Astrophysicists

Post by bystander » Thu Jan 18, 2018 7:11 pm

Neutron-Star Merger Yields New Puzzle for Astrophysicists
NASA | Chandra X-ray Observatory | McGill University | 2018 Jan 18

Afterglow from cosmic smash-up continues to brighten, confounding expectations
[c][imghover=http://chandra.si.edu/press/18_releases/gw.jpg]http://chandra.si.edu/press/18_releases/gw_label.jpg[/imghover]Credit: NASA/CXC/McGill/J.Ruan et al.[/c][hr][/hr]
The afterglow from the distant neutron-star merger detected last August has continued to brighten – much to the surprise of astrophysicists studying the aftermath of the massive collision that took place about 138 million light years away and sent gravitational waves rippling through the universe.

New observations from NASA's orbiting Chandra X-ray Observatory, reported in Astrophysical Journal Letters, indicate that the gamma ray burst unleashed by the collision is more complex than scientists initially imagined.

"Usually when we see a short gamma-ray burst, the jet emission generated gets bright for a short time as it smashes into the surrounding medium – then fades as the system stops injecting energy into the outflow," says McGill University astrophysicist Daryl Haggard, whose research group led the new study. "This one is different; it's definitely not a simple, plain-Jane narrow jet." ...

Brightening X-Ray Emission from GW170817/GRB 170817A: Further Evidence for an Outflow - John J. Ruan et al
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Gravitational Wave Event Likely Signaled Creation of a Black Hole (GW170817)

Post by bystander » Sat Jun 02, 2018 2:59 pm

Gravitational Wave Event Likely Signaled Creation of a Black Hole
NASA | MSFC | SAO | Chandra X-ray Observatory | 2018 May 31
The spectacular merger of two neutron stars that generated gravitational waves announced last fall likely did something else: birthed a black hole. This newly spawned black hole would be the lowest mass black hole ever found, as described in our latest press release.

After two separate stars underwent supernova explosions, two ultra-dense cores (that is, neutron stars) were left behind. These two neutron stars were so close that gravitational wave radiation pulled them together until they merged and collapsed into a black hole. The artist's illustration shows a key part of the process that created this new black hole, as the two neutron stars spin around each other while merging. The purple material depicts debris from the merger. An additional illustration shows the black hole that resulted from the merger, along with a disk of infalling matter and a jet of high-energy particles.

A new study analyzed data from NASA's Chandra X-ray Observatory taken in the days, weeks, and months after the detection of gravitational waves by the Laser Interferometer Gravitational Wave Observatory (LIGO) and gamma rays by NASA's Fermi mission on August 17, 2017.

X-rays from Chandra are critical for understanding what happened after the two neutron stars collided. The question is: did the merged neutron star form a larger, heavier neutron star or a black hole? ...

GW170817 Most Likely Made a Black Hole - David Pooley et al
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Re: First Light from a Gravitational Wave Event (GW170817)

Post by neufer » Sat Jun 02, 2018 3:56 pm

https://en.wikipedia.org/wiki/Rotating_black_hole wrote: <<A rotating black hole is a black hole that possesses angular momentum. In particular, it rotates about one of its axes of symmetry. Rotating black holes are formed in the gravitational collapse of a massive spinning star or from the collapse of a collection of stars or gas with a total non-zero angular momentum. As most stars rotate it is expected that most black holes in nature are rotating black holes.

In late 2006, astronomers reported estimates of the spin rates of black holes in The Astrophysical Journal. A black hole in the Milky Way, GRS 1915+105, may rotate 1,150 times per second (i.e., C# : two octives above middle C), approaching the theoretical upper limit.

The formation of a rotating black hole by a collapsar is thought to be observed as the emission of gamma ray bursts.

A rotating black hole can produce large amounts of energy at the expense of its rotational energy. This happens through the Penrose process in the black hole's ergosphere, an area just outside its event horizon. In that case a rotating black hole gradually reduces to a Schwarzschild black hole, the minimum configuration from which no further energy can be extracted.>>
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Re: First Light from a Gravitational Wave Event (GW170817)

Post by MarkBour » Mon Jun 04, 2018 3:20 am

BDanielMayfield wrote:
Thu Oct 19, 2017 3:28 pm
This was and is a great confirmation of expectations as to the site of heavy element production in the universe.

Recipe for making gold, uranium, etc.:
  • (1) Condense two close orbiting massive stars out of interstellar medium.
    (2) Allow cores of two stars to cook light elements up to iron.
    (3) Return excess gas and light elements back to interstellar medium via core collapse supernovae, producing binary neutron star pair.
    (4) Allow orbital decay to bring two neutron stars into contact, producing kilonova.
Alchemy is easy, if you have enough time and material.

Bruce
And what element is the neutron star itself? Atomic number 0, apparently. This element has many stable isotopes, ranging from

1E+570Z . . . to . . . 4E+570Z . . . :-)
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Re: First Light from a Gravitational Wave Event (GW170817)

Post by BDanielMayfield » Tue Jun 05, 2018 2:12 pm

MarkBour wrote:And what element is the neutron star itself? Atomic number 0, apparently. This element has many stable isotopes, ranging from

1E+570Z . . . to . . . 4E+570Z . . . :-)
Neutronium, of course. :ssmile: But only stable under the extreme conditions inside neutron stars. If the entire star was nothing but neutrons they couldn't be so magnetic. :idea:

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ESA: Cosmic Blast Takes Rest at Last (GW170817)

Post by bystander » Tue Jun 05, 2018 2:55 pm

Cosmic Blast Takes Rest at Last
ESA Science & Technology | XMM-Newton | 2018 May 31

Last year, the first detection of gravitational waves linked to a gamma-ray burst triggered a vast follow-up campaign with ground and space telescopes to study the aftermath of the neutron star merger that gave rise to the explosion. ESA's XMM-Newton observations, obtained a few months after the discovery, caught the moment when its X-ray emission stopped increasing, opening new questions about the nature of this peculiar source.

The Evolution of the X-ray Afterglow Emission of GW 170817 / GRB 170817A in XMM-Newton Observations - P. D'Avanzo et al
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Re: First Light from a Gravitational Wave Event (GW170817)

Post by MarkBour » Tue Jun 05, 2018 3:48 pm

What are the odds that a neutron star collision produces a neutron star, as opposed to a black hole? Is it close to 50% ?

Is there a known/expected distribution of sizes for neutron stars? And perhaps they don't get much chance to interact beyond a single pair that may have formed as a binary ... still, in a globular cluster or a galactic center, perhaps there are lots of them in proximity. Presumably if they have a combined mass of about 4 Sols, they will have enough mass that their product will form a black hole, rather than a larger neutron star. How different would that event appear to LIGO ?
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Re: First Light from a Gravitational Wave Event (GW170817)

Post by neufer » Tue Jun 05, 2018 3:52 pm

BDanielMayfield wrote:
Tue Jun 05, 2018 2:12 pm
MarkBour wrote:
And what element is the neutron star itself? Atomic number 0, apparently. This element has many stable isotopes, ranging from

1E+570Z . . . to . . . 4E+570Z . . . :-)
Neutronium, of course. :ssmile: But only stable under the extreme conditions inside neutron stars. If the entire star was nothing but neutrons they couldn't be so magnetic. :idea:
https://en.wikipedia.org/wiki/Neutronium wrote:

<<Neutronium [Nu] is a hypothetical substance composed purely of neutrons. The word was coined by scientist Andreas von Antropoff in 1926 (before the discovery of the neutron) for the conjectured "element of atomic number zero" that he placed at the head of the periodic table. It was subsequently placed in the middle of several spiral representations of the periodic system for classifying the chemical elements, such as those of Charles Janet (1928), E. I. Emerson (1944), John D. Clark (1950) and in Philip Stewart's Chemical Galaxy (2005). However, the meaning of the term has changed over time, and from the last half of the 20th century onward it has been also used to refer to extremely dense substances resembling the neutron-degenerate matter theorized to exist in the cores of neutron stars; hereinafter "degenerate neutronium" will refer to this. The term "neutronium" has been popular in science fiction since at least the middle of the 20th century. It typically refers to an extremely dense, incredibly strong form of matter. While presumably inspired by the concept of neutron-degenerate matter in the cores of neutron stars, the material used in fiction bears at most only a superficial resemblance, usually depicted as an extremely strong solid under Earth-like conditions, or possessing exotic properties such as the ability to manipulate time and space. In contrast, all proposed forms of neutron star core material are fluids and are extremely unstable at pressures lower than that found in stellar cores. According to one analysis, a neutron star with a mass below about 0.2 solar masses would explode.

Although the term is not used in the scientific literature either for a condensed form of matter, or as an element, there have been reports that, besides the free neutron, there may exist two bound forms of neutrons without protons. If neutronium were considered to be an element, then these neutron clusters could be considered to be the isotopes of that element. However, these reports have not been further substantiated.
  • Mononeutron: An isolated neutron undergoes beta decay with a mean lifetime of approximately 15 minutes (half-life of approximately 10 minutes), becoming a proton (the nucleus of hydrogen), an electron and an antineutrino.

    Dineutron: The dineutron, containing two neutrons was unambiguously observed in the decay of beryllium-16, in 2012 by researchers at Michigan State University. It is not a bound particle, but had been proposed as an extremely short-lived state produced by nuclear reactions involving tritium. It has been suggested to have a transitory existence in nuclear reactions produced by helions (helium 3 nuclei, completely ionised)that result in the formation of a proton and a nucleus having the same atomic number as the target nucleus but a mass number two units greater. The dineutron hypothesis had been used in nuclear reactions with exotic nuclei for a long time. Several applications of the dineutron in nuclear reactions can be found in review papers. Its existence has been proven to be relevant for nuclear structure of exotic nuclei. A system made up of only two neutrons is not bound, though the attraction between them is very nearly enough to make them so. This has some consequences on nucleosynthesis and the abundance of the chemical elements.

    Tetraneutron: A tetraneutron is a hypothetical particle consisting of four bound neutrons. Reports of its existence have not been replicated.
Although not called "neutronium", the National Nuclear Data Center's Nuclear Wallet Cards lists as its first "isotope" an "element" with the symbol n and atomic number Z = 0 and mass number A = 1. This isotope is described as decaying to element H with a half life of 10.24±0.02 min. Due to the beta (β−) decay of mononeutron and extreme instability of aforementioned heavier "isotopes", neutron matter is not expected to be stable under ordinary pressures.>>
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Re: First Light from a Gravitational Wave Event (GW170817)

Post by neufer » Tue Jun 05, 2018 4:16 pm

MarkBour wrote:
Tue Jun 05, 2018 3:48 pm

What are the odds that a neutron star collision produces a neutron star, as opposed to a black hole? Is it close to 50% ?

Is there a known/expected distribution of sizes for neutron stars? And perhaps they don't get much chance to interact beyond a single pair that may have formed as a binary ... still, in a globular cluster or a galactic center, perhaps there are lots of them in proximity. Presumably if they have a combined mass of about 4 Sols, they will have enough mass that their product will form a black hole, rather than a larger neutron star. How different would that event appear to LIGO ?
https://en.wikipedia.org/wiki/GW170817 wrote:
<<GW170817 was a gravitational wave (GW) signal produced by the last minutes of two neutron stars spiralling closer to each other and finally merging. A hypermassive neutron star is believed to have formed initially and then collapsed into a black hole within milliseconds, as evidenced by:
  • the large amount of ejecta (much of which would have been swallowed by an immediately forming black hole) and

    the lack of evidence for emissions being powered by neutron star spin-down, which would occur for longer-surviving neutron stars.>>
A neutron star collision should produces a stable neutron star if:
the mass of the colliding neutron star minus the mass of the gravitational radiation is 3 M or less:
https://en.wikipedia.org/wiki/Neutron_star#Mass_and_temperature wrote:
<<A neutron star has a mass of at least 1.1 and perhaps up to 3 solar masses (M☉). The maximum observed mass of neutron stars is about 2.01 M. But in general, compact stars of less than 1.39 M (the Chandrasekhar limit) are white dwarfs, whereas compact stars with a mass between 1.4 M and 3 M (the Tolman–Oppenheimer–Volkoff limit) should be neutron stars (though there is an interval of a few tenths of a solar mass where the masses of low-mass neutron stars and high-mass white dwarfs can overlap). Between 3 M and 5 M, hypothetical intermediate-mass stars such as quark stars and electroweak stars have been proposed, but none have been shown to exist. Beyond 10 M the stellar remnant will overcome the neutron degeneracy pressure and gravitational collapse will usually occur to produce a black hole, though the smallest observed mass of a stellar black hole is about 5 M.

The temperature inside a newly formed neutron star is from around 1011 to 1012 kelvin. However, the huge number of neutrinos it emits carry away so much energy that the temperature of an isolated neutron star falls within a few years to around 106 kelvin. At this lower temperature, most of the light generated by a neutron star is in X-rays.>>
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Re: First Light from a Gravitational Wave Event (GW170817)

Post by BDanielMayfield » Tue Jun 05, 2018 4:44 pm

neufer wrote:
Tue Jun 05, 2018 4:16 pm
MarkBour wrote:
Tue Jun 05, 2018 3:48 pm

What are the odds that a neutron star collision produces a neutron star, as opposed to a black hole? Is it close to 50% ?

Is there a known/expected distribution of sizes for neutron stars? And perhaps they don't get much chance to interact beyond a single pair that may have formed as a binary ... still, in a globular cluster or a galactic center, perhaps there are lots of them in proximity. Presumably if they have a combined mass of about 4 Sols, they will have enough mass that their product will form a black hole, rather than a larger neutron star. How different would that event appear to LIGO ?
https://en.wikipedia.org/wiki/GW170817 wrote:
<<GW170817 was a gravitational wave (GW) signal produced by the last minutes of two neutron stars spiralling closer to each other and finally merging. A hypermassive neutron star is believed to have formed initially and then collapsed into a black hole within milliseconds, as evidenced by:
  • the large amount of ejecta (much of which would have been swallowed by an immediately forming black hole) and

    the lack of evidence for emissions being powered by neutron star spin-down, which would occur for longer-surviving neutron stars.>>
A neutron star collision should produces a stable neutron star if:
the mass of the colliding neutron star minus the mass of the gravitational radiation is 3 M or less:
https://en.wikipedia.org/wiki/Neutron_star#Mass_and_temperature wrote:
<<A neutron star has a mass of at least 1.1 and perhaps up to 3 solar masses (M☉). The maximum observed mass of neutron stars is about 2.01 M. But in general, compact stars of less than 1.39 M (the Chandrasekhar limit) are white dwarfs, whereas compact stars with a mass between 1.4 M and 3 M (the Tolman–Oppenheimer–Volkoff limit) should be neutron stars (though there is an interval of a few tenths of a solar mass where the masses of low-mass neutron stars and high-mass white dwarfs can overlap). Between 3 M and 5 M, hypothetical intermediate-mass stars such as quark stars and electroweak stars have been proposed, but none have been shown to exist. Beyond 10 M the stellar remnant will overcome the neutron degeneracy pressure and gravitational collapse will usually occur to produce a black hole, though the smallest observed mass of a stellar black hole is about 5 M.

The temperature inside a newly formed neutron star is from around 1011 to 1012 kelvin. However, the huge number of neutrinos it emits carry away so much energy that the temperature of an isolated neutron star falls within a few years to around 106 kelvin. At this lower temperature, most of the light generated by a neutron star is in X-rays.>>
Low mass double neutron star mergers (over billions of years) in which the end product isn't a black hole must be relatively common. Otherwise, the heavy elements only produced by them wouldn't be nearly as widespread as they apparently are.

Bruce
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