Text on screen - 'NASA Astrophysics.' Shot of stars twinkling in space. Suddenly one multiplies in size, emitting a massive burst of light.
NARRATOR:
Every day or two, on average, satellites detect a massive explosion somewhere in the sky. These are gamma ray bursts, the brightest blasts in the universe. They're thought to be caused by jets of matter moving near the speed of light associated with the birth of black holes. Gamma ray bursts that last longer than two seconds are the most common and are thought to result from the death of a massive star. Shorter bursts prove much more elusive. In fact, even some of their basic properties were unknown until NASA's Swift satellite began work in 2004. Astronomers suspected that crashing neutron stars could explain short bursts. A neutron star is what remains when a star several times the mass of the sun collapses and explodes. With more than the sun's mass packed into a sphere less than 18 miles across, these objects are incredibly dense. Just a sugar cube-sized piece of neutron star can weigh as much as all the water in The Great Lakes. When two orbiting neutron stars collide, they merge and form a black hole, releasing enormous amounts of energy in the process.
A computer-generated model shows two yellow stars circling each other, then colliding. An orange and red explosion swirls outwards. A dense white ball remains in the centre labelled 'Black Hole'.
NARRATOR:
Armed with state-of-the-art super-computer models, scientists have shown that colliding neutron stars can produce the energetic jet required for a gamma ray burst. Earlier simulations demonstrated that mergers can make black holes. Others had shown that the high-speed particle jets needed to make a gamma ray burst would continue if placed in the swirling wreckage of a recent merger.
The computer-generated model shows two yellow stars colliding again, and merging. Bands form around the merged stars and pulsate outwards, forcing red-coloured matter to explode and swirl into space.
NARRATOR:
Now the simulations reveal the middle step of the process, how the merging star's magnetic field organises itself into outwardly directed components capable of forming a jet. The Damiana super-computer at Germany's Max Planck Institute for Gravitational Physics needed six weeks to reveal the details of a process that unfolds in just 35 thousandths of a second.
The Damiana super-computer's model of two stars colliding and forming a black hole plays. On the left side, a swirling red cloud becomes denser and denser. On the right, yellow explodes out with blue swirling around it.
NARRATOR:
The new simulation shows two neutron stars merging to form a black hole surrounded by super-hot plasma. On the left is a map of the density of the stars as they scramble their matter into a dense hot cloud of swirling debris. On the right is a map of the magnetic fields with blue representing a magnetic strength a billion times greater than the sun's.
Another simulation plays. This time the stars are represented by yellow balls with circular white squiggles inside. The two stars collide and the squiggles fragment and twist around each other, then form dense, tangled branches up and down from the centre, jetting out into space.
NARRATOR:
The simulation shows the same disorderly behaviour of the matter and magnetic fields. Both structures gradually become more organised, but what's important here is the white magnetic field. Amidst this incredible turmoil, the white field has taken on the character of a jet, although no matter is flowing through it when the simulation ends. Showing that chaotic magnetic fields suddenly become organised as jets provides scientists with the missing link. It confirms that merging neutron stars can indeed produce short gamma ray bursts. At this moment, somewhere across the cosmos, it's about to happen again.
Text on screen - 'NASA Goddard Space Flight Center. www.nasa.gov/goddard'