blogtecaolivelli

ASTRONEWS

fonte: Internet

Astronews a cura di Massimiliano Razzano

• What Happens When Three Black Holes Collide?

The consequences of two black holes colliding may be huge,

 the energy produced by such a collision could even be 

detected by observatories here on Earth. Ripples in space-

time will wash over the Universe as gravitational waves

 and are predicted to be detected as they pass through

the Solar System. Taking this idea one step further, what

 would happen if three black holes collide? Sound like science

fiction? Well it's not, and there is observational evidence that

 three black holes can cluster together, possibly colliding after

 some highly complex orbits that can only be calculated by the

 most powerful computers available to researchers...

Back in January 2007, a quasar triplet was observed

 over 10 billion light years away. Quasars are generated

 by the supermassive black holes eating away at the

core of active galaxies. Using the powerful W. M. Keck

Observatory, researchers from Caltech were able to peer

 back in time (10 billion years) to see a period in the

 Universe's life when active galaxies and black hole

 mergers would have been fairly common events

 (when compared to the calmer Universe of today).

They observed three tightly packed quasars, an

unprecedented discovery.

Now, scientists Manuela Campanelli, Carlos Lousto and

Yosef Zlochower, all working at Rochester Institute of

 Technology's Center for Computational Relativity and

Gravitation, have simulated the highly complex mechanisms

behind three interacting and merging supermassive black

holes, much like the situation observed by Keck in 2007.

 The same group have worked on calculating the collision

of two black holes before and have written a code that is

 powerful enough to simulate the collision of up to 22 black

holes. However, 22 black holes probably wouldn't collide

 naturally, this simply demonstrates the stability of the code,

"Twenty-two is not going to happen in reality, but three or

 four can happen," says Yosef Zlochower, an assistant

professor. "We realized that the code itself really didn't

care how many black holes there were. As long as we

could specify where they were located - and had enough

 computer power - we could track them."

These simulations are of paramount importance to the

gravitational wave detectors such as the

 Laser Interferometer Gravitational-Wave Observatory (LIGO).

 So far there has been no firm evidence to come from

these detectors, but more time is needed, the LIGO

 detector requires several years of "exposure time"

to collect enough data and remove observational "noise".

 But what do gravitational wave astronomers look for?

This is the very reason many different cosmic scenarios

 are being simulated so the characteristics of events like

 two or three black holes mergers can be identified from

their gravitational wave signature.

• 09/04/2008 - A Case of MOND Over Dark Matter