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Category: cosmology – Page 271

At the heart of almost every sufficiently massive galaxy there is a black hole whose gravitational field, although very intense, affects only a small region around the center of the galaxy. Even though these objects are thousands of millions of times smaller than their host galaxies, our current view is that the Universe can be understood only if the evolution of galaxies is regulated by the activity of these black holes, because without them the observed properties of the galaxies cannot be explained.

Theoretical predictions suggest that as these black holes grow they generate sufficient energy to heat up and drive out the gas within to great distances. Observing and describing the mechanism by which this energy interacts with galaxies and modifies their is therefore a basic question in present day Astrophysics.

With this aim in mind, a study led by Ignacio Martín Navarro, a researcher at the Instituto de Astrofísica de Canarias (IAC), has gone a step further and has tried to see whether the matter and energy emitted from around these black holes can alter the evolution, not only of the host galaxy, but also of the satellite galaxies around it, at even greater distances. To do this, the team has used the Sloan Digital Sky Survey, which allowed them to analyze the properties of the galaxies in thousands of groups and clusters. The conclusions of this study, started during Navarro’s stay at the Max Planck Institute for Astrophysics, are published today in Nature magazine.

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A ball of gas around the Milky Way’s black hole has sparked a new debate. Could it be a massive puff of dark matter?

The orbit of S2 and its stellar companions indicated that they were circling around a massive object, about 4 million times the mass of the Sun. Although astronomers could not directly see the object, they knew it could only be one thing.

By 1974, the object, eventually dubbed Sagittarius A*, was more or less solidified as your own local supermassive black hole. Since then, scientists have made several follow-up observations to reestablish the existence of this dark, lurking beast in the Milky Way — even turning one of the largest virtual telescopes in the world on it.

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When a massive star dies, first there is a supernova explosion. Then, what’s left over becomes either a black hole or a neutron star.

That neutron star is the densest celestial body that astronomers can observe, with a mass about 1.4 times the size of the sun. However, there is still little known about these impressive objects. Now, a Florida State University researcher has published a piece[1] in Physical Review Letters arguing that new measurements related to the neutron skin of a lead nucleus may require scientists to rethink theories regarding the overall size of neutron stars.

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Smashing together lead particles at 99.9999991 percent the speed of light, scientists have recreated the first matter that appeared after the Big Bang.

Out of the wreck came a primordial type of matter known as quark-gluon plasma, or QGP. It only lasted a fraction of a second, but for the first time, scientists were able to probe the plasma’s liquid-like characteristics – finding it to have less resistance to flow than any other known substance – and determine how it evolved in the first moments in the early Universe.

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New research is helping to explain one of the big questions that has perplexed astrophysicists for the past 30 years — what causes the changing brightness of distant stars called magnetars.

Magnetars were formed from stellar explosions or supernova e and they have extremely strong magnetic field s, estimated to be around 100 million, million times greater than the magnetic field found on earth.

The magnetic field on each magnetar generates intense heat and x-rays. It is so strong it affects the physical properties of matter, most notably the way that heat is co nducted through the crust of the star and across its surface, creating the variations in brightness which has puzzled astrophysicists and astronomers.

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A team at Stony Brook University used ORNL’s Summit supercomputer to model x-ray burst flames spreading across the surface of dense neutron stars.

At the heart of some of the smallest and densest stars in the universe lies nuclear matter that might exist in never-before-observed exotic phases. Neutron stars, which form when the cores of massive stars collapse in a luminous supernova explosion, are thought to contain matter at energies greater than what can be achieved in particle accelerator experiments, such as the ones at the Large Hadron Collider and the Relativistic Heavy Ion Collider.

Although scientists cannot recreate these extreme conditions on Earth, they can use neutron stars as ready-made laboratories to better understand exotic matter. Simulating neutron stars, many of which are only 12.5 miles in diameter but boast around 1.4 to 2 times the mass of our sun, can provide insight into the matter that might exist in their interiors and give clues as to how it behaves at such densities.

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