Monday, October 16, 2017

Kilonovas: Now the Evidence

Nature of Science 
History of Science

WaPo's Sarah Kaplan and Ben Guarino report on the collision of two collapsed stars that happened only recently when one thinks of time in terms of the universe. A mere 130 million years ago (mya). Like yesterday.

The result was a "kilonova," a merger of two neutron stars and is the first time this event has ever been observed, the "first cosmic event in history to be observed via both traditional telescopes...and gravitational wave detectors...". Unitl this event, kilonovas have been theoretical (This event demonstrates the power of a robust theoretical framework.). Neutron stars are composed of neutral particles and the collisons are the source of heavy elements such as gold, platinum and silver.

Julie McEnery, a NASA astrophysicist at Goddard Space Flight Center (Greenbelt, Md.) involved in this work is noted that this find is "transformational," and now scientists will be "able to combine dramatically different ways of viewing the universe, and I think our level of understanding is going to leap forward as a result." This new science is called "multimessenger astrophysics."

Kaplan and Guarino describe the fascination and excitement of the race to find the source of the signal. Scientists studying such events are constrained by the mechanics of the universe. First, it is a needle in a haystack event. Secondly, the haystack is on the move (as the universe races outward from us) so the signal grows more and more faint. There is a very short open window--about an hour--to observe this event before it disappears from view.

This place, the universe is big and fast.

Kaplan and Guarino  write that the "events... hewed closely to theories about the merger of neutraon stars based in nuclear physics, general relativity and research on the origins of elements." Ryan Foley, one of the scientists involved said that "'as a civilization (we) have been confined to the Earth, and almost all the information we've ever received from the universe has been through light. Yet we were able to predict...things as extreme as two neutron stars colliding when even the idea of neurtron stars was incredible.'"

McEnery put it this way. "While I'm not surprised that Einstein is right, it's always nice to see him pass another test." Here is the WaPo article which includes visualizations of the event.

Here are some of the numbers: 70 laboratories and telescopes around the world and ~ 4500 authors of the paper published in the Astrophysical Journal Letters. They represent 910 institutions.This is not the largest collaboration ever.

There is also another report from NPR with animations that include how "it actually looked to astronomers." I especially liked this view. I think the two reports, WaPo and NPR complement one another and that both deserve a look so please at least scan them if you want to know more.

Nell GreenfieldBoyce, the author of the NPR essay calls attention to one thing most of us might be interested in: the gold, the platinum and the silver produced resulting from this mash-up.

She writes "Now to the scale of the debris.'That debris is strange stuff,' according to theoretician Daniel Kasen.'It's gold and platinum but it's mixed in with what you'd call just regular radioactive waste, and there's this big radioactive wast cloud that just starts mushrooming out from the merger site. It starts out small, about the size of a small city, but it's moving so fast--a few tenths of the speed of light--that after a day it's a cloud the size of the solar system.'"

GreenfieldBoyce writes that "according to (Kasen's) estimates, this neutron star collision produced around 200 Earth masses of pure gold, and maybe 500 Earth masses of platinum." 'It's a ridiculously huge amount on human scale.' Kasen wears a platinum wedding ring and notes that 'it's crazy to think that these things that seem very far out and kind of exotic actually impact the world and us in kind of intimate ways.'"

Earth masses represent a lot of tons, way more than I'm prepared to calculate. Atlas would struggle. One Earth mass equals 5.972x10^24 kg. The ^ represents to the power of 24.

Calculate away at heart's content!

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