Archive for July 8, 2013

New Knowledge About Early Galaxies

The early galaxies of the universe were very different from today’s galaxies. Using new detailed studies carried out with the ESO Very Large Telescope and the Hubble Space Telescope, researchers, including members from the Niels Bohr Institute, have studied an early galaxy in unprecedented detail and determined a number of important properties such as size, mass, content of elements and have determined how quickly the galaxy forms new stars. The results are published in the scientific journal, Monthly Notices of the Royal Astronomical Society.

“Galaxies are deeply fascinating objects. The seeds of galaxies are quantum fluctuations in the very early universe and thus, understanding of galaxies links the largest scales in the universe with the smallest. It is only within galaxies that gas can become cold and dense enough to form stars and galaxies are therefore the cradles of starsbirths”, explains Johan Fynbo, professor at the Dark Cosmology Centre at the Niels Bohr Institute at the University of Copenhagen.

In today’s galaxies, we have a lot of stars and less gas. In the early galaxies, there was a lot of gas and fewer stars.

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Blitzars: Fast Radio Bursts From Supramassive Rotating Neutron Stars

Image Credit: Nasa

Image Credit: Nasa

Radio telescopes have picked up some bright radio flashes that appear for only a brief moment on the sky and do not repeat (Thornton et al. 2013, Science). So, what causes these unusual radio signals? We suggest in a recent paper (Falcke & Rezzolla 2013, that this could be the final farewell greetings of a supramassive rotating neutron star (SURON) collapsing into a black hole and shedding its magnetic field.

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Cosmic Dust Belts Without Dust

Planets and asteroids, red giants and brown dwarfs – there are all kinds of objects in our Universe. Debris disks are among them. These are belts consisting of countless dust particles and planetesimals, circling around one central star. “At least one fifth of stars are surrounded by dust belts like these,” Prof. Dr. Alexander Krivov from the Friedrich-Schiller-University Jena explains. “They are the remains of the formation of planets, in which the unused, building materials are collected,” the astrophysicist points out. Therefore debris disks are an important piece in the puzzle to be able to better understand the variety of planetary systems.

For astronomers like Alexander Krivov debris disks are actually nothing new. Our sun is also orbited by such dust belts: the Asteroid Belt and the Kuiper Belt with Pluto being perhaps the most well-known object in it. However, the Jena astrophysicist, accompanied by an international team of scientists, has observed six stars similar to the sun with extraordinary dust belts: The newly discovered debris disks are not only bigger than the Kuiper Belt. Above all they are extremely cold. With a temperature of about minus 250 °C they are the coldest debris disks known so far. The scientists report on it in the science journal ‘The Astrophysical Journal’, which is already online and will be available in a print version from 20 July. “We were surprised that such cold debris disks exist at all,” Alexander Krivov, the lead author of the new study, says. By way of comparison: The Kuiper Belt is about 70 °C degree warmer, some of the dust disks even reach room temperature.

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Using The Sun To Illuminate A Basic Mystery Of Matter

While antiparticles can be created and then detected with costly and complex particle-accelerator experiments, such particles are otherwise very difficult to study. However, Fleishman and the two co-researchers have reported the first remote detection of relativistic antiparticles — positrons — produced in nuclear interactions of accelerated ions in solar flares through the analysis of readily available microwave and magnetic-field data obtained from solar-dedicated facilities and spacecraft. That such particles are created in solar flares is not a surprise, but this is the first time their immediate effects have been detected.

The results of this research have far-reaching implications for gaining valuable knowledge through remote detection of relativistic antiparticles at the Sun and, potentially, other astrophysical objects by means of radio-telescope observations. The ability to detect these antiparticles in an astrophysical source promises to enhance our understanding of the basic structure of matter and high-energy processes such as solar flares, which regularly have a widespread and disruptive terrestrial impact, but also offer a natural laboratory to address the most fundamental mysteries of the universe we live in.

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Cosmic Radio Bursts Point To Cataclysmic Origins In The Distant Universe

Mysterious bursts of radio waves have been detected that appear to have originated from billions of light years away. They have left scientists pondering what may have caused them. An international team of researchers including scientists from the Max Planck Institute for Radio Astronomy in Bonn could rule out any terrestrial origin for the four discovered fast radio bursts. Their brightness and distance estimates indicate that the bursts originated at cosmological distances, when the Universe was just 6 to 9 billion years old. The emission process for these bursts is not known yet.

Four Fast Radio Bursts or FRBs with durations of only a few milliseconds were detected at high Galactic latitudes in the southern sky.

The extremely short duration of the bursts and the inferred great distance imply that they have been caused by some cataclysmic cosmological event, such as two merging neutron stars or a star dying or being swallowed by a black hole.

The results point to some of the most extreme events in astrophysics involving large amounts of mass or energy as the source of the radio bursts. “A single burst of radio emission of unknown origin was detected outside our galaxy about six years ago but no one was certain what it was or even if it was real, so we have spent the last four years searching for more of these explosive, short-duration radio bursts”, says Dan Thornton, the University of Manchester and Commonwealth Scientific and Industrial Research Organisation PhD student who led the study. “This paper describes four more bursts, removing any doubt that they are real. And the furthest one we detected after a light travelling time of about 8 billion years.”

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