Neutron Star Collision was detected by LIGO

[T.G.G. Moogly]

Kilonovas - Another Round Goes to Einstein

Neutron Star merger produces gravity waves, Gold and Platinum

Scientists have detected the warping of space generated by the collision of two dead stars, or neutron stars.

They have confirmed that such mergers lead to the production of the gold and platinum that exists in the Universe.

The measurement of the gravitational waves given off by this cataclysmic event was made on 17 August by the LIGO-VIRGO Collaboration.
The discovery enabled telescopes all over the world to capture details of the merger as it unfolded.

How can stars that are dead act so alive? /snark

 

[Jimmy Higgins]

link

Looks like the rumors were true.

NASA's Fermi telescope, which detects gamma rays, sent out the first alarm. Then, 1.7 seconds later, gravity wave detectors in Louisiana and Washington state that are a part of the LIGO Laboratory , whose founders won a Nobel Prize earlier this month, detected the crash. It issued a worldwide alert to focus telescopes on what became the most well-observed astronomical event in history.

130 million light years away and the scientists were able to detect it via two independent methods, within 1.7 seconds of each other. The post collision event lasted a few weeks. An extraordinary find as the was observed post collision for a period of a few weeks!

 

[Tom Sawyer]

Well, that's embarrassing. A whole fucking universe of empty space, but the one time the two stars crash into each other, it's when someone is watching them.

 

[Underseer]

Well, that's embarrassing. A whole fucking universe of empty space, but the one time the two stars crash into each other, it's when someone is watching them.

But no one was watching them at the time the collision occurred, only now.

 

[Loren Pechtel]

Obviously God can't steer.

 

[DBT]

Good thing they weren't neighbors, could have done some serious damage.

 

[Loren Pechtel]

Question: I see neutron star collisions reported as a source of some heavy elements. I don't understand this.

The minimum mass for a neutron star is 1.4 solar masses. That means an impact is at least 2.8 solar masses. That's awfully close to black hole territory--how are the heavy elements being liberated if they are created?

 

[Jimmy Higgins]

Question: I see neutron star collisions reported as a source of some heavy elements. I don't understand this.

The minimum mass for a neutron star is 1.4 solar masses. That means an impact is at least 2.8 solar masses. That's awfully close to black hole territory--how are the heavy elements being liberated if they are created?

Well, that'd be the 1.4 and 1.4 solar masses colliding that'd do that.

 

[bilby]

Question: I see neutron star collisions reported as a source of some heavy elements. I don't understand this.

The minimum mass for a neutron star is 1.4 solar masses. That means an impact is at least 2.8 solar masses. That's awfully close to black hole territory--how are the heavy elements being liberated if they are created?

The same way that when you drop a MOAB it makes a HUGE hole, but for some reason, not all of the ejected debris falls back into the hole.

 

[repoman]

I wonder what the radial and tangential velocity of the two neutron stars were as they swirled around their barycenter at the point of impact.

 

[Loren Pechtel]

Question: I see neutron star collisions reported as a source of some heavy elements. I don't understand this.

The minimum mass for a neutron star is 1.4 solar masses. That means an impact is at least 2.8 solar masses. That's awfully close to black hole territory--how are the heavy elements being liberated if they are created?

The same way that when you drop a MOAB it makes a HUGE hole, but for some reason, not all of the ejected debris falls back into the hole.

A MOAB blast doesn't have an escape velocity that's almost lightspeed (or, if the stars are much above the minimum, an escape velocity above lightspeed.)

- - - Updated - - -

I wonder what the radial and tangential velocity of the two neutron stars were as they swirled around their barycenter at the point of impact.

The tangential velocity is a large fraction of lightspeed.

 

[bilby]

The same way that when you drop a MOAB it makes a HUGE hole, but for some reason, not all of the ejected debris falls back into the hole.

A MOAB blast doesn't have an escape velocity that's almost lightspeed (or, if the stars are much above the minimum, an escape velocity above lightspeed.)

Doesn't matter.

A MOAB blast doesn't accelerate debris to above escape velocity at all.

What it does do is accelerate some of the material in such a direction and at such a speed that it doesn't fall in the radius of the crater. (Okay, it's not a very good analogy; sorry)

When neutron stars collide, forming a black hole, a significant amount of material is outside the Schwarzschild radius, and being subjected to huge accelerations, at the time that the black hole starts to form; The hole will capture whatever is inside the new event horizon, plus a sizable fraction of whatever is outside; but the event horizon is far smaller than the radii of the two contributing stars, and so a big chunk of matter will be ejected at initial velocities far in excess of the local escape velocity (even where that escape velocity is a sizable fraction of c).

The high temperatures and pressures that make heavy element formation possible also make the escape of at least some of that material inevitable - and you don't need a particularly large percentage of a pair of neutron stars to make up enough heavy elements to build a good number of rocky planets. Rocky planets mass in the order of one millionth of the mass of even medium sized stars, and most of the mass of a planet like Earth or Venus is light elements (Iron or lighter). The fraction of the heavy element production of the collision that needs to escape is going to be in the order of a billionth or less of the total mass involved, if you want to make enough heavy stuff to mix with a lot of hydrogen in order to build a solar system like our own. After all, it's not like trans-ferric elements are particularly significant as a fraction of the total mass of the Solar System.

 

[lpetrich]

The two neutron stars likely spiraled into each other. As they did so, they got distorted into squashed American-football shapes, with one end pointing to the other and the other end pointing away. Thus, some of their substance would have gotten pulled off into the nearby space. It would then have expanded, pushing itself outward even more.

Its superabundance of neutrons means that some of them would decay into protons, producing very heavy nuclei. Including those of silver, gold, platinum, thorium, and uranium.

 Stellar nucleosynthesis shows which elements were likely produced by which sources.

 

[Tom Sawyer]

/mod

 

[repoman]

This is a very solid layman video about it if you want to explain it easily. Also many footnote links.