[ExI] Gravitational waves made by colliding neutron stars found

[John Clark]

The rumors were true. On Aug 17 at 8:41 a.m. Eastern Daylight Time (Aug 18
12:41: Universal Time) LIGO and VIRGO detected a Gravitational Wave coming
from the collision of 2 neutron stars  of 1.1 and 1.6 solar
masses. LIGO/VIRGO immediately alerted other astronomers to look at the
region around galaxy NGC 4993 130 million light years away for anything
unusual, but the orbiting Chandra X-ray Observatory had already found a
short gamma ray burst from NGC 4993. Soon after that optical astronomers in
Chile and the  Hubble Space Telescope saw blue spot in NGC 4993 that wasn't
there just days before, radio telescopes also saw unusual stuff.

This time the gravitational wave lasted about 100 seconds, the Black Hole
collisions they saw before only lasted  about a second; at the start of
that 100 seconds the 2 stars were orbiting only 200 miles apart. It's not
clear if the merged object is a Black Hole or a larger Neutron star, the
transition between the 2 is thought to be between 2.5 and 4 solar masses
but the exact
​transition ​
point is not known.
​ ​But it is thought
 that the event synthesized and ejected 40 to 100 earth masses of Gold and
10 to 30 earth masses of Uranium.

Astronomers were very lucky, all 3 gravitational detectors were online at
the same time for only a few weeks but that's when this event happened, and
its the closest short gamma ray burst ever found.

https://www.ligo.caltech.edu/page/press-release-gw170817

John K Clark
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