Wednesday, October 18, 2017

GW170817 - A truly great day in science

I am sure we have all heard about the astounding discovery revealed two days ago (if not here is a good YouTube vid about it).  

I also managed to find this interesting summary data slide on AMVA4NP . People are saying this is the beginning of "Multi-Messenger Astrophysics". 



This is a really busy slide - but as you can see on it, the neutron star coalescence was observed in a galaxy approx 150 MLY away.  This kind of event releases a lot of energy and its called a Kilonova.

The event generated a massive electromagnetic emission (Gamma Ray Burst, X-ray burst, UV etc...) . You can see what this looked like on various cameras (bottom). The big black spot is the galactic center - there are millions of stars emitting light in there. And the two black lines are where we see light from the kilonova event. You can see it is almost as intense as the galactic center in some images. This really brings out how much energy was released in this event. I am guessing it probably vaporized thousands of star systems in a 100+ LY ball around it.

There is going to be a lot of discussion around this in the months and years to come, but I want to bring up one point which you can all see in the top left part of the slide.

The Gravitational Waves (GW) arrived a full 14 seconds before Gamma Ray Burst (GRB). I am assuming that the time stamps on LIGO and the GRS are well aligned but as both GW and GRB travel at the speed of light, this implies that the space time distortion caused by the event predated the electromagnetic jetting phenomena (which is where a GRB arises) by about 12-14 seconds. The space time distortion peaked a full 2s before the GRB jet developed and escaped the surface of the coalesced stellar mass.

There is some amazing high energy density physics to be modeled here. We are going to learn a lot from the differences in time between these signals.

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