Astronomers unravel a blast that sent ripples in space-time | Hacker News Reader

Astronomers unravel a blast that sent ripples in space-time

delta.tudelft.nl

43 pointskartikkumar25 comments

>"During such events, massive amounts of heavy metals are formed. This collision, for instance, produced a lump of gold with the mass of our planet in just a split second."

We need to find a localized wormhole and go mine that.

Yeah and watch inflation sky-rocket: https://en.wikipedia.org/wiki/Price_revolution

yeah but you still get to sell it even as your yields decrease

death spirals are still profitable for the issuer

Lowering price of materials allow the creation of new and more goods, so it's always a good thing

How is gold created out of the collision of stars composed of neutrons?

If you smash proton and neutron clumps the size of stars together you get fragments that are gold-sized.

That makes a little more sense. The original quote suggests that a single very large lump of gold was created, not a very large number of separate gold atoms.

This raises the question of why gold tends to be found near other gold on Earth.

Is there an answer to that question? And, why is the distribution of matter not random? Maybe some sort of gravitational grouping? (eg earth's iron core, centrifugal enrichment of uranium). Or affinity for some orientation relative to field states, magnetism/diamagnetism etc.?

Like attracts?

As I understand it, the distribution was decided when the earth was still hot. So the mechanics you're interested in are those of high-temperature solutions containing liquid gold, which I don't understand that much. There's other interesting phenomena too, like gold frequently occurs in quartz rocks[0].

[0] https://www.quora.com/Why-is-gold-frequently-located-in-quar...

I'm not a geologist at all, but when you freeze soda you tend to get water ice infused with veins of high-sugar soda concentrate. I wouldn't be surprised if similar mechanisms tend to lump matter with similar melting points together in molten rock.

> This raises the question of why gold tends to be found near other gold on Earth.

When you spin a combination of stuff that is "loose enough" at sufficient speeds, the centrifugal force acts on the constituent masses differently. As a result similar masses coalesce.

This is the same principle used to separate and concentrate (enrich) all kinds of stuff in centrifuges.

Deep in the earth matter tends to clump together by density, just as oil separates from water due to density. There is still some dynamism though so temporary mixing does occur.

Gold at earth's surface tends to be found in deposits where water with gold particles in it was flowing through a crack for an extended period of time.

Over time some of the gold is deposited on the sides of the crack, essentially concentrating it through evaporation and deposition.

These cracks then become what miners call 'veins'. Other metals and minerals have similar stories.

TLDR: water from deep in the earth carries gold particles upward. Cracks form consistent flows which concentrate deposits over time.

Materials separate by MACROSCOPIC density. However, heavy elements can be chemically bound in light materials. Uranium, for example, is highly concentrated in the Earth's crust compared to the mantle.

Good point, although I believe gold is usually found in its elemental form (although sometimes alloyed with other metals).

I didn't know that fact about U, thanks.

Gold is a siderophile element, chemically favoring to bind with iron metal, and preferentially went into the Earth's iron core when the planet differentiated.

This is why mining asteroids for siderophiles (like gold, but also platinum group elements) has been a staple of space advocacy.

>How is gold created out of the collision of stars composed of neutrons?

They are composed predominantly out of neutrons. Some percentage of their composition is still electrons and assorted atomic nuclei, which is a non-trivial amount of matter considering the common range of density they tend to have.

I would imagine all kinds of interesting(strange?) interactions take place when such dense and energetic objects collide.

Neutronium (degenerate neutron fluid) is only stable at immense pressure.

Relieve that pressure -- by flinging bits into space in a collision or explosion -- and it reverts to neutrons + protons + electrons + antineutrinos, forming first ultramassive nuclei, which rapidly decay to stable elements, many being heavy elements well above iron in atomic number.

The nuclei mar be formed by r-capture (rapid capture), or perhaps devolve from dense neutronium clumps.

https://www.nature.com/articles/nature04807

https://en.wikipedia.org/wiki/Neutronium

"The vision of VLBI is so sharp that if people were playing table tennis on the Moon we would see the moves of the ping pong ball. "

I was under the impression that a radio telescope could only take a single pixel image. Are they using a different kind of receiver that can create a complete image? If so, how can they still increase resolution using interference?

It's a raster scan. Larger images are built one pixel at a time.

I think he was talking about angular resolution. EM wave arrives at different antennas at slightly different time. The phase difference allows for very high resolution of the direction the wave is coming from. [VLBI](https://en.m.wikipedia.org/wiki/Very-long-baseline_interfero...) effectively produces an antenna with an aperture the size of the Earth. To make it work one needs extremely accurate time synchronization and spatial location. In the interview he talked about continental drift of several millimeters per year. Those are the things they need to compensate for.

A sibling comment mentions raster scanning: building up an image one pixel at a time. That is largely true for a single telescope (though it is possible to have an array of receivers taking multiple pixels at the same time).

However, VLBI is an array of telescopes. Using interferometry - measuring the interference pattern of the signals of each pair of telescopes - we get simultaneous data on a variety of angular scales and orientations. As the Earth turns, the sky appears to turn, and more points in the UV plane can be measured. Once you have enough data, you can essentially get an image by doing a Fourier transform of the data.

Kudos to the scientists, astronomers and engineers who made this possible. This is so amazing. The reference to being able to see Ping balls on moon is unbelievable. We have such brilliant people in our midst!

To add another moon reference, a cell phone on the moon would be the third brightest radio source in the sky.

To add another moon reference: A normal cell phone on the moon would be the third brightest radio source in the sky.

"In 2015 gravitational waves were detected that resulted from a collision of supermassive black holes."

"The 2015 discovery was an event of another physical nature, much more powerful than the 2017 one, as it included the collision of supermassive black holes, each of the order of 100 millions of solar masses"

This is not true. GW150914 was from the collision of two black holes of ~30 solar masses each.

Reply on news.ycombinator.com