PRESENTER: There was a new announcement from
LIGO, the Laser Interferometer Gravitational-Wave
Observatory, recently. Gravitational waves
were first predicted by Einstein. They’re
ripples in the fabric of space that move at
the speed of light, created by huge events
– like colliding stars or black holes. Despite
the magnitude of these events, Einstein thought
it would impossible to observe them. However,
100 years later, scientists did find them.
Two black holes collided, creating gravitation
waves that were picked up by LIGO. This week,
they announced a fifth detection. But this
one is different, as Astronomer Royal, Professor
Lord Martin Rees explained to Graihagh Jackson.
MARTIN: Well is more interesting because,
in this case, what was colliding was not two
black holes but two neutron stars. Neutron
stars are stars that weigh a bit more than
the Sun but are only about ten miles across,
so very very dense. They collide and splash
together rather like two black holes do. But
when black holes collide, you don’t see
anything else because a black hole is, essentially,
just much curved space. When two neutron stars
collide, you expect to see a lot of evidence
for this collision in other ways: optical
light, X rays, etc. What is exciting about
this event is that they detected the gravitational
wave from the merger but, less than two seconds
afterwards, a gamma ray flash was detected
from the same object. Since that time, about
70 different observatories have been looking
at the afterglow from this event to try to
understand what’s actually going on, and
it’s very complicated physics.
The announcement was made last Monday and
the lead paper has 3,000 authors which is,
I think, a record at least for astronomy,
and those are the 1300 authors involved in
the LIGO experiment and the gravitational
wave experiment called VIRGO in Italy. Plus
also the many hundreds involved in the other
observatories which have looked in all other
wavebands for evidence of this follow-up.
They’ve been observing this object, which
is in a galaxy about 100 million light years
away for the last couple of months – it
was actually detected on August 17th.
