My name is Dr. Jess McIver.
I'm a senior postdoc here at Caltech
working for the LIGO laboratory.
So I think about gravitational wave astrophysics
and I also think about the noise in the LIGO detectors.
So you have these two compact objects — black holes, neutron stars — and they're orbiting around each other
and they're radiating energy away 
in the form of gravitational waves.
And as they do this, their orbit decreases
So that sound — the pitch, the frequency — is increasing until they merge.
Well, there's more than one kind of chirp!
It could go ...woooooooop...
or it could go ...woop...
so I sort of mimic from a low-mass system
We call it the chirp mass, so it's some function of the product of the two masses and
the sum of the two component masses,  the two
objects that are spinning around coalescing.
And that governs the evolution of the chirp over time
and it's that signature that we can use to
infer what the masses are
and once we know what the masses are, we can use that to infer what the objects are.
General relativity predicts the form
that these waves should have,
So if I have two black holes or two neutron stars, 
then I can use general relativity
to calculate exactly what that wave form
should look like.
And what's really cool about gravitational waves is, unlike light where you expect a light to be
interfered with by dust or other lights,
gravitational waves will propagate largely unaffected
through very vast distance. 
So we can tell that a signal is liklely to be
a neutron star - black hole, or 
two neutron stars merging,
or two black holes merging because
the signature of the masses of these objects is imprinted on the waves.
