Page 18 - 2013 Annual Report

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From the big bang to neutron stars and black holes, Perimeter
research into strong gravity explores cosmic cataclysms powerful
enough to warp the fabric of spacetime. These areas of space where
gravity is extremely strong serve as a natural experiment where
researchers can theoretically “test” the validity of our current theory of
gravity (Einstein’s general relativity) and investigate alternative theories.
Perimeter researchers also seek to understand and characterize the
ways that curved or dynamical spacetimes are connected to other
fundamental questions of physics.
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research
Escape From the Black Hole
It is a cosmic monster of almost unfathomable power.
Gobbling up anything that dares come near it – even light – the black
hole at the centre of an elliptical galaxy called Messier 87 (M87)
never relinquishes a victim.
It is more than six billion times more massive than our sun. It is 50
million light years from Earth. Nothing that crosses its “point of no
return,” the event horizon, can escape its grasp.
Peering over this precipice with an enormous network of connected
telescopes, a team of international scientists including
Perimeter
Associate Faculty member Avery Broderick
has, for the first time
ever, measured the event horizon of a black hole outside of our
galaxy.
The team observed that the M87 black hole blasts collimated (that is,
narrow and extremely fast) jets of material at velocities approaching
the speed of light, dramatically altering the environment around it.
The observations – made by linking radio telescopes in Hawaii,
Arizona, and California to create a highly precise eye on the cosmos
called the Event Horizon Telescope – are the first to capture this jet-
launching region of a black hole.
Such measurements, combined with follow-up work that will link
even more radio telescopes worldwide, will provide crucial insights
into the origins, evolution, and fates of these voracious cosmic
giants.
On a Collision Course
Whereas Broderick and his international collaborators have tracked
the cataclysmic force of a massive black hole,
Perimeter Faculty
member Luis Lehner
has, in a sense, listened for the birth cries of
black holes.
Lehner and collaborators studied how two compact objects in a
binary system, such as black holes or neutron stars, combine to
create a single new entity.
In some cases, a neutron star orbiting a black hole gets swallowed
up by its neighbour’s gravitational pull; sometimes, two neutron stars
spiral ever closer to one another before violently colliding to create
a new black hole.
The gravitational force behind both events is tremendously
powerful, packing masses equivalent to that of the sun into spheres
smaller than most cities; electromagnetic forces create powerful
electromagnetic signals.
Strong Gravity
Credit: ESO/L. Calçada