Simulation done on Einstein’s general theory of relativity may lead to answer why universe expands?

pic 1
The gravitational waves generated during the formation of structures in the universe is shown. The structures (distribution of masses) are shown as bright dots, gravitational waves by ellipses. the sizes of the ellipse is proportional to the amplitude of the wave and its orientation represents its polarization.

‘Universe is constantly expanding’, a statement that I hope all the astrophysicists and the cosmologists are familiar with. But the fascinating question lies in how does our universe evolve? We know that Universe merges everything that comes its way, but the topic of ‘evolution of universe’ is still a very enigmatic point in the vast field of cosmology.

But, with the discovery of Gravitational waves, all new kinds of coded simulation is going on in order to fully understand the formation of structures of the Universe. One such success is recently achieved by the physicists from the University of Geneva, where based on Einstein’s equations, they integrated the space-time rotation into their calculations and calculate the amplitude of gravitational waves, thus providing a new code of numerical simulation that offers a glimpse of the complex process of the formation of structures in the Universe.

Before the discovery of the gravitational waves, physicists studied the
formation of large-scale cosmological structures based on Newtonian gravitation. The principal of these codes hypothesizes that space itself does not change, it is said to be motionless, while time goes on. Thus, the Newtonian-based codes were applicable when the matter of the particles was moving very slowly (say about 300km per second).
However, the code failed to show accurate calculations when the speed of the matters was quite high. Moreover, the Newtonian numerical simulation does not describe dark energy’s fluctuations. Constituting 70% of the total energy of the Universe, it does not doubt that dark energy is responsible for the accelerated expansion of the Universe. Therefore, it was essential to find a new way to simulate the establishment of cosmological structures and sanction the study of these two phenomena.

Thus, Physicists from the University of Geneva successfully generated a code, named evolution and simulated the numerical codes based on Einstein’s theory of relativity. Unlike the Newtonian theory, the theory of relativity suggests that space and time are constantly changing. The most important advantage of this simulation is that now scientists can accurately calculate the fast-moving particles in space. The aim was to forecast the amplitude and the impact of gravitational waves and space-time’s rotation induced by the formation of cosmological structures.

To generate the code, the physicists analyzed a cubic part in space, consisting of 60 billion zones with each containing a particle. Thorough analyzing of particles was done with respect to their neighbors using an LATfield2 library which solves nonlinear partial differential equations. A supercomputer was also used to detect the motion of particles and calculate the metric (the measure of distances and time between two galaxies in the Universe) using Einstein’s equations. The calculations were then analyzed and compared to the Newtonian’s numerical simulation results. Finally, the effect of frame-dragging (the rotation of space-time) and gravitational waves was introduced by the formation of structure in the Universe.

It is the first time that frame-dragging and gravitational waves were being included in a numerical cosmological simulation. This operation opened a new way of testing the general theory of relativity as well as unlocking the mysteries behind Universe’s expansion.

NOTE: The above picture is copyrighted by Mr.Ruth Durrer of UNIGE.

Advertisements

Black Holes ejects matter into Cosmic abysses

pic 1

Cosmos is a complicated subject with a multitude of fascinating objects ranging from carbonaceous dust grains to quasars, but that don’t stop the cosmologists’ curiosity to stop thinking and researching about the most abysmal concepts of the Universe. We all live in a universe subjugated by unseen matters such as baryons, CMB photons, Cold Dark Matter (CDM), Dark Energy and all these species of the universe are concentrated into filaments that expanse around the brink of colossal voids.

Thought to be almost void until now, a group of scientists have come to conclusions that dark holes could contain as much as 20% of the ‘normal’ matter in the cosmos and that galaxies make up only 1/500th of the volume of the universe. Observing the cosmic microwave radiation and analyzing it, modern satellite observatories like COBE, WMAP and Planck have advanced our understanding of the universe’s composition. Current measurements suggest that ‘normal’ matter (i.e. the matter that makes up stars, planets, baryons, gas and dust) combine almost 4.9% of the total universe, whereas mysterious and unseen ‘dark’ matter join 26.8% and mysterious ‘dark energy’ constitute 68.3% of the universe.

Some fundamental research work mapped the positions of galaxies and their allied dark matter over large volumes, showing that they are in strings that make up a ‘cosmic web’. The scientific team explored it further, using data from the Illustris project, which is a large computer simulation of the evolution and formation of galaxies, used to measure the mass and volume of these strings and the galaxies within them.

Illustris simulates a cube of space in the universe, computing some 350 million light years on each side. It took the first variable as the age of a young universe, just 12 million years old, and the second variable was a small fraction of its current age. The data’s were simulated and the gravity and flow of matter changing the structure of the cosmos up to the present day were analysed. The simulation compacts with both normal and dark matter, with the most important effect being the gravitational pull of the dark matter.

After analyzing the data, the scientists concluded that 50% of the total mass of the universe is in the places where galaxies exist in, trampled into a volume of 0.2% of the universe we see, and a further 44% is in the enveloping strings. Just 6% is in the voids, which make up 80% of the volume.

pic 2

The most surprising thing that caught scientists’ attention were the 20% fraction of ‘normal’ matter filling up the voids. Super-massive black holes found at the center of galaxies are the reason behind this. Matters fall into the holes, thus getting converted into energy. The energy is then delivered into the surrounding gases and leads to enormous outflows of matter, expanding for hundreds of thousands of light years from the black holes, reaching far beyond the size of their host galaxies.

The result will not only help us to know about how voids with more ‘normal’ matter are filled than expected but might also explain the missing baryon problem, where astronomers do not see the amount of normal matter predicted by their models.

Further simulations using Illustris have been done, and the results are expected to come within few months, which will give us an auxiliary understanding of black holes and confirm the output. Whatever the outcome, it will be hard to see the matter in the voids, as this is likely to be fragile and too casual to emanate the X-rays that would make it detectable by satellites.

Galactic climate being affected by Black Holes

A prevailing galactic explosion produced by a giant black hole situated almost 26 million light years away from Earth has provoked a new leap in the field of cosmology. This is one of the nearest super-massive black holes to Earth and its frequent violent outbursts can somehow change the galactic climate is been proposed by a team of researchers led by Eric Schlegel, Professor of Physics at The University of Texas at San Antonio.

burping-black-hole
The inset image shows X-ray arcs that astronomers say are signs of galactic burping in the Messier 51 galaxy system

Schlegel’s team used NASA’s Earth-orbiting Chandra X-ray Observatory to locate the black hole blast in the famous Messier 51 system of galaxies. The Messier 51 system contains a large spiral galaxy, NGC 5194, colliding with a smaller companion galaxy, NGC 5195.

“Just as powerful storms here on Earth impact their environments, so too do the ones we see out in space,” Schlegel said. “This black hole is blasting hot gas and particles into its surroundings that must play an important role in the evolution of the galaxy.”

Schlegel and his colleagues, including Fisk University graduate student and UTSA alumna Laura Vega, detected two X-ray emission arcs near to the center of NGC 5195, where the super-massive black hole is located.

“We think these arcs represent artifacts from two enormous gusts when the black hole expelled material outward into the galaxy,” said co-author Christine Jones, astrophysicist, and lecturer at the Harvard-Smithsonian Center for Astrophysics. “We think this activity has had a big effect on the galactic landscape.”

The researchers detected a willowy region of hydrogen gas emission just beyond the outer arc, suggesting that X-ray emitting gas expatriate the hydrogen gas from the center of the galaxy.

Furthermore, the properties of the gas around the arcs propose that the outer arc has flounced up enough material to trigger the formation of new stars. This type of phenomenon, where a black hole affects its host galaxy, is called feedback. Continue reading