- On August 17th,
something special happened.
For the first time, we
detected gravitational waves
that were coming not from
the collision of black holes,
but from the collision
of two neutron stars.
A neutron star is what's left after a star
burns all of its fuel and
implodes under its own weight.
One hundred and thirty
five million years ago,
in a galaxy far, far away,
called NGC4993,
two neutron stars were inspiralling,
they were rotating around each other.
They got as close as the
distance between Atlanta
and Nashville when they started merging.
As they were spiraling faster and faster,
they were stretching
and squeezing spacetime.
They produced a gravitational wave signal
that kept traveling all the way
to us, and then they merged.
As they merged, they produced
a fireball of gamma radiation.
That light also traveled
all the way to us,
and the residual matter
that was left behind
started merging in nuclear reactions
in this process that's called a kilonova,
and they produce heavy
elements, such as iron and gold.
The gravitational waves
reached the two LIGO detectors
and the VIRGO detector.
They produced almost imperceptible
changes in the length
of the three detectors,
and that was detected
as a gravitational wave
signal by LIGO and VIRGO.
About two seconds after the
gravitational waves arrived
to LIGO and VIRGO, the Fermi
satellites detected a burst
of gamma radiation that was
coming from an area of the sky
that was consistent with
the gravitational waves.
Within about 40 minutes,
telescopes and satellites
all over the world were
alerted of this event,
and they started their followup campaign,
and this is gonna give us important clues
in where heavy elements are formed,
how matter as we know is
formed, and which processes.
This is very exciting, because
we are really making use
of both the gravitational wave
and the electromagnetic wave
information to learn new things.
We have really unlocked this
new window into the universe,
and we are making the
best use possible of it.
