[ RadSafe ] Hebrew University Team Uncovers Origin of Heavy Elements in the Universe

[Brennan, Mike (DOH)]

An article I read a while ago pointed out that neutron star collisions undoubtedly happen, but that direct hits are much more unlikely than gravitational capture, followed by a "death spiral" in which the two bodies move faster and faster the closer they get to common center of mass.  Such large masses accelerating like that would have interesting effects on local space-time.

Of even bigger interest is when the super-massive black holes at the center of galaxies collide.  The article said that there is one such event occurring/has occurred (tense is hard when talking about something billions of light years away).  The two black hole are now circling at less than a year per revolution, and moving at a speed between "fast" and "my goodness!".  Calculations are that they will collide/merge/implode/something in about 20 years.  Astrophysicist admit that there models do not predict what will happen, and some of them whimper and cringe when asked to do so.  On the bright side, we don't have to worry about it ending the universe, because if it does there is nothing we can do about it.

-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of KARAM, PHILIP
Sent: Monday, December 14, 2015 7:07 AM
To: The International Radiation Protection (Health Physics) Mailing List
Subject: Re: [ RadSafe ] Hebrew University Team Uncovers Origin of Heavy Elements in the Universe

Interesting piece, and it adds a bit to the existing thinking by adding a new source of Pu-244. But it still seems likely that a great deal of Pu-244 is formed in supernovae, with the binary neutron star mergers adding to the supernova-produced material.

One thing, too, to consider is that the Solar System is in a "superbubble" - an area of space in which cosmic gas and dust concentrations are much lower than is typical in our galaxy. One line of thinking is that this superbubble was carved out by a series of supernovae a few tens of millions of years ago - the shock waves from the supernovae are thought to have propelled the gas and dust from this area. So one reason for the paucity of Pu-244 that was mentioned could well be the Solar System's presence in a part of space that is abnormally clear of debris. 

The reason for the early Solar System containing a bunch of Pu-244 (as mentioned in this piece) could be that the dust cloud from which the Solar System formed was, itself, supernovae debris and the impetus for it to begin collapsing into the Sun and planets was most likely being struck by the shock wave from another supernova. So it's not surprising that the earliest Solar System would have elevated levels of this nuclide.

Anyhow - it seems most reasonable to think that Pu-244 is formed in supernovae AND in binary star mergers; the supernovae would provide the "background" Pu-244 and the binary star mergers would punctuate that with occasional injections of larger amounts. 

Andy


P. Andrew Karam, PhD, CHP
NYPD Counterterrorism
One Police Plaza, Room 1109
New York, NY 10038
(718) 615-7055 (desk)
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-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of ROY HERREN
Sent: Sunday, December 13, 2015 6:15 AM
To: radsafe
Subject: [ RadSafe ] Hebrew University Team Uncovers Origin of Heavy Elements in the Universe

http://new.huji.ac.il/en/article/28210
Hebrew University Team Uncovers Origin of Heavy Elements in the Universe _______________________________________________
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