Scientists led by Durham
University's Institute for Computational Cosmology ran the huge cosmological
simulations that can be used to predict the rate at which gravitational waves
caused by collisions between the monster black holes might be detected.
The amplitude and frequency of these
waves could reveal the initial mass of the seeds from which the first black
holes grew since they were formed 13 billion years ago and provide further
clues about what caused them and where they formed, the researchers said.
The research is being presented
today (Monday, June 27, 2016) at the Royal Astronomical Society's National
Astronomy Meeting in Nottingham, UK. It was funded by the Science and
Technology Facilities Council, the European Research Council and the Belgian
Interuniversity Attraction Poles Programme.
The study combined simulations from
the EAGLE project - which aims to create a realistic simulation of the known
Universe inside a computer - with a model to calculate gravitational wave
signals.
Two detections of gravitational
waves caused by collisions between supermassive black holes should be possible
each year using space-based instruments such as the Evolved Laser
Interferometer Space Antenna (eLISA) detector that is due to launch in 2034,
the researchers said.
In February the international LIGO
and Virgo collaborations announced that they had detected gravitational waves
for the first time using ground-based instruments and in June reported a second
detection.
As eLISA will be in space - and will
be at least 250,000 times larger than detectors on Earth - it should be able to
detect the much lower frequency gravitational waves caused by collisions
between supermassive black holes that are up to a million times the mass of our
sun.
Current theories suggest that the
seeds of these black holes were the result of either the growth and collapse of
the first generation of stars in the Universe; collisions between stars in
dense stellar clusters; or the direct collapse of extremely massive stars in
the early Universe.
As each of these theories predicts
different initial masses for the seeds of supermassive
black hole seeds, the collisions would produce different
gravitational wave signals.
This means that the potential
detections by eLISA could help pinpoint the mechanism that helped create
supermassive black holes and when in the history of the Universe they formed.
"These waves are caused by
massive collisions between objects with a mass far greater than our sun.
"By combining the detection of
gravitational waves with simulations we could ultimately work out when and how
the first seeds of supermassive black holes formed."
Co- author Professor Richard Bower,
of Durham University's Institute for Computational Cosmology, added:
"Black holes are fundamental to galaxy formation and are thought to sit at
the centre of most galaxies, including our very own Milky Way.
"Discovering how they came to
be where they are is one of the unsolved problems of cosmology and astronomy.
"Our research has shown how
space based detectors will provide new insights into the nature of supermassive
black
holes."
Gravitational waves were first
predicted 100 years ago by Albert Einstein as part of his Theory of General
Relativity.
The waves are concentric ripples
caused by violent events in the Universe that squeeze and stretch the fabric of
space time but most are so weak they cannot be detected.
LIGO detected gravitational waves
using ground-based instruments, called interferometers, that use laser beams to
pick up subtle disturbances caused by the waves.
eLISA will work in a similar way,
detecting the small changes in distances between three satellites that will
orbit the sun in a triangular pattern connected by beams from lasers in each
satellite.
In June it was reported that the
LISA Pathfinder, the forerunner to eLISA, had successfully demonstrated the
technology that opens the door to the development of a large space observatory
capable of detecting gravitational waves in space.
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