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Language: en
due to the crazy technological
challenges that had to be overcome in
order to detect gravitational waves some
people were skeptical that scientists
had actually done it that they'd
actually seen gravitational waves from
black holes after all there was no
corroboration but after the discovery
this being announced today there can be
no more doubt because scientists have
detected the merging of two neutron
stars a hundred and thirty million light
years away this is the first ever
detection of gravitational waves from in
spiraling neutron stars and what's
really exciting about this detection is
that the same event has been observed
with telescopes in all areas of the
electromagnetic spectrum it all began on
August 17th at 8:41 a.m. Eastern Time
when LIGO interferometer --zz identified
a clear gravitational wave signal that
lasted about a hundred seconds which is
way longer than any previous detection
and it's consistent with theoretical
predictions for the signal from two
merging neutron stars around one point
seven seconds later NASA's Fermi
gamma-ray telescope identified a burst
of gamma rays for decades gamma-ray
bursts have been thought to come from
neutron star mergers but the evidence
has been lacking to know for sure that
these gravitational waves and the gamma
ray burst came from the same event the
key was to locate where in the sky this
neutron star merger occurred unlike a
merger of black holes neutron stars emit
light when they smash together and
continue emitting electromagnetic
radiation afterwards the Fermi gamma-ray
Space Telescope identified a large patch
of the sky roughly the size of six
thousand full moons using the European
Space Agency's integral gamma ray
satellite they were able to narrow down
that range now the gravitational waves
detected by LIGO allowed them to
identify two long strips in the sky one
of which overlapped with the existing
search area now interestingly Virgo
which is the newest gravitational wave
detector which is in Italy it was online
at the time and it should have easily
been able to detect these gravitational
waves in yet
it saw almost nothing and that was kind
of a key clue because it indicated that
the gravitational waves must be coming
from one of that detectors blind spots
every interferometer has some blind
spots where if the waves are coming at
that angle its symmetric
with respect to the two arms and so it
just can't be detected so this helped
further narrow the search area down to
the size of about 144 full moons now
within that area around fifty galaxies
were identified to be studied with
optical telescopes and just 11 hours
after the initial detection astronomers
located a bright spot in the galaxy NGC
for 993 you are seeing here pictures of
the light from two neutron stars that
merged 130 million years ago watch how
the color and brightness changes in the
aftermath of the collision so what are
neutron stars well they're the leftover
cores of big stars that have exploded
they've gone supernova
now those remaining cores are squeezed
down by gravity and if they're too big
say larger than two or three solar
masses well they will keep on getting
crushed until they collapse in on
themselves forever and become a black
hole but if those cores are a little
smaller say 1.1 and 1.6 times the mass
of our Sun as they were in this case
well then they get squeezed still and so
electrons merge with protons to form
neutrons and neutrinos and the neutrinos
take off and the neutrons are left in a
really really densely packed star and
the only reason the neutrons don't
combine with each other is because of a
quantum principle the Pauli exclusion
principle that basically says you can't
put two of these particles right on top
of each other and that's actually the
only thing holding that neutron star up
so if you have two of these neutron
stars and they are orbiting each other
well then they emit some of their energy
as gravitational waves and as they do
that they lose energy meaning they
spiral in closer to each other
and when they get really close to a few
hundred kilometers apart the
gravitational waves become intense
allowing us to detect them hundreds of
millions of light years away the
collision of neutron stars creates a
killer nova which spews debris out into
space
this is debris that glows allowing us to
observe what's been created and in fact
the new observations with light
telescopes have shown that heavy
elements like gold lead and platinum
were made in this event and that
helps us understand where a lot of the
heavy elements in our universe come from
in my view this event really shows us
that we're in a new age of astronomy we
can detect gravitational waves not just
from black holes but now from neutron
stars we can use that information to
locate places in the sky where that
occurred and we can validate that with
our other telescopes looking in all
parts of the electromagnetic spectrum so
now we really have more tools to
understand our universe and I just can't
wait for the questions that we're gonna
address next and all of the different
things we're gonna be able to study as
the gravitational wave observatory z'
get better and better it's a phenomenal
time to be studying the universe
you