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Posts Tagged ‘Galaxies

Interview with Lucio Mayer on world’s first realistic simulation of the formation of Milky Way

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First glimpse into birth of the Milky Way – For almost 20 years astrophysicists have been trying to recreate the formation of spiral galaxies such as our Milky Way realistically. Now astrophysicists from the University of Zurich present the world’s first realistic simulation of the formation of our home galaxy together with astronomers from the University of California at Santa Cruz. The new results were partly calculated on the computer of the Swiss National Supercomputing Center (CSCS) and show, for instance, that there has to be stars on the outer edge of the Milky Way.

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August 30, 2011 at 6:25 pm

Step Up to the Barred Spiral Galaxy

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The Canada-France-Hawaii Telescope in Hawaii sees the barred spiral galaxy NGC 2903 almost face-on in this photograph. The central bulge glows yellow with older stars, while the spiral arms contain younger stars as determined by their blue color, and star formation regions of red.
http://www.space.com/34-image-day.html

Written by physicsgg

August 30, 2011 at 5:30 pm

Posted in ASTRONOMY

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ERIS: World’s first realistic simulation of the formation of the Milky Way

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— After nine months of number-crunching on a powerful supercomputer, a beautiful spiral galaxy matching our own Milky Way emerged from a computer simulation of the physics involved in galaxy formation and evolution. The simulation by researchers at the University of California, Santa Cruz, and the Institute for Theoretical Physics in Zurich solves a longstanding problem that had led some to question the prevailing cosmological model of the universe.

This image of the Eris simulation shows the stars in the galaxy as observers would see it. Blue colors are regions of recent star formation, while redder regions are associated with older stars. The spiral arms are typically star-forming, and the central bulge is basically "red and dead."

“Previous efforts to form a massive disk galaxy like the Milky Way had failed, because the simulated galaxies ended up with huge central bulges compared to the size of the disk,” said Javiera Guedes, a graduate student in astronomy and astrophysics at UC Santa Cruz and first author of a paper on the new simulation, called “Eris.” The paper has been accepted for publication in the Astrophysical Journal.

The Eris galaxy is a massive spiral galaxy with a central “bar” of bright stars and other structural properties consistent with galaxies like the Milky Way. Its brightness profile, bulge-to-disk ratio, stellar content, and other key features are all within the range of observations of the Milky Way and other galaxies of the same type. “We dissected the galaxy in many different ways to confirm that it fits with observations,” Guedes said…. Read the rest of this entry »

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August 30, 2011 at 12:45 am

Galaxies Are Running out of Gas: Why the Lights Are Going out in the Universe

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A CSIRO study has shown why the lights are going out in the Universe. The Universe forms fewer stars than it used to, and a CSIRO study has now shown why: the galaxies are running out of gas.

A star-forming region in a nearby galaxy, imaged by the Hubble Space Telescope

Dr Robert Braun (CSIRO Astronomy and Space Science) and his colleagues used CSIRO’s Mopra radio telescope near Coonabarabran, NSW, to study far-off galaxies and compare them with nearby ones.

Light (and radio waves) from the distant galaxies has taken time to travel to us, so we see the galaxies as they were between three and five billion years ago.

Galaxies at this stage of the Universe’s life appear to contain considerably more molecular hydrogen gas than comparable galaxies in today’s Universe, the research team found.

Stars form from clouds of molecular hydrogen. The less molecular hydrogen there is, the fewer stars will form.

The research team’s paper is in press in Monthly Notices of the Royal Astronomical Society.

Astronomers have known for at least 15 years that the rate of star formation peaked when the Universe was only a few billion years old and has declined steeply ever since.

“Our result helps us understand why the lights are going out,” Dr Braun said.

“Star formation has used up most of the available molecular hydrogen gas.”

After stars form, they shed gas during various stages of their lives, or in dramatic events such as explosions (supernovae).

This returns some gas to space to contribute to further star formation.

“But most of the original gas — about 70% — remains locked up, having been turned into things such as white dwarfs, neutron stars and planets,” Dr Braun said….. Read the rest of this entry »

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August 22, 2011 at 7:46 pm

Cosmic Exclamation Point

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VV 340, also known as Arp 302, provides a textbook example of colliding galaxies seen in the early stages of their interaction. The edge-on galaxy near the top of the image is VV 340 North and the face-on galaxy at the bottom of the image is VV 340 South. Millions of years later these two spirals will merge — much like the Milky Way and Andromeda will likely do billions of years from now. Data from NASA’s Chandra X-ray Observatory (purple) are shown here along with optical data from the Hubble Space Telescope (red, green, blue). VV 340 is located about 450 million light years from Earth.
http://www.nasa.gov

Written by physicsgg

August 12, 2011 at 2:33 pm

Posted in ASTRONOMY

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A Spiral in Leo

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This new picture from ESO’s Very Large Telescope shows NGC 3521, a spiral galaxy located about 35 million light years away in the constellation of Leo (The Lion). Spanning about 50 000 light-years, this spectacular object has a bright and compact nucleus, surrounded by richly detailed spiral structure.

The most distinctive features of the bright galaxy NGC 3521 are its long spiral arms that are dotted with star-forming regions and interspersed with veins of dust. The arms are rather irregular and patchy, making NGC 3521 a typical example of a flocculent spiral galaxy. These galaxies have “fluffy” spiral arms that contrast with the sweeping arms of grand-design spirals such as the famous Whirlpool galaxy or M 51, discovered by Charles Messier.

NGC 3521 is bright and relatively close-by, and can easily be seen with a small telescope such as the one used by Messier to catalogue a series of hazy and comet-like objects in the 1700s. Strangely, the French astronomer seems to have missed this flocculent spiral even though he identified several other galaxies of similar brightness in the constellation of Leo.

It was only in the year that Messier published the final version of his catalogue, 1784, that another famous astronomer, William Herschel, discovered NGC 3521 early on in his more detailed surveys of the northern skies.  Through his larger, 47-cm aperture, telescope, Herschel saw a “bright center surrounded by nebulosity,” according to his observation notes.

In this new VLT picture, colourful, yet ill defined, spiral arms replace Herschel’s “nebulosity”. Older stars dominate the reddish area in the centre while young, hot blue stars permeate the arms further away from the core.

Oleg Maliy, who participated ESO’s Hidden Treasures 2010 competition [1], selected the data from the FORS1 instrument on ESO’s VLT at the Paranal Observatory in Chile that were used to create this dramatic image. Exposures taken through three different filters that passed blue light (coloured blue), yellow/green light (coloured green), and near-infrared light (coloured red) have been combined to make this picture. The total exposure times were 300 seconds per filter. Oleg’s image of NGC 3521 was a highly ranked entry in the competition, which attracted almost 100 entries.

Notes

[1] ESO’s Hidden Treasures 2010 competition gave amateur astronomers the opportunity to search through ESO’s vast archives of astronomical data, hoping to find a well-hidden gem that needed polishing by the entrants. To find out more about Hidden Treasures, visit http://www.eso.org/public/outreach/hiddentreasures/.

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August 10, 2011 at 11:53 am

Posted in ASTRONOMY

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Triplet Galaxies Revealed by World’s Most Advanced Telescope

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The bright galaxies NGC 3628, M 65, and M 66 lie within the constellation Leo. Europe’s VLT Survey telescope’s 268-megapixel camera grabbed this wide angle image, expected to yield insight into dark matter and the odd behavior of galactic halos.

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July 27, 2011 at 7:56 pm

Posted in ASTRONOMY, COSMOLOGY

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Was the universe born spinning?

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This Hubble telescope image shows the spiral NGC 4414 galaxy, some 60 million light-years away. It is one of the many spiral galaxies that have a preferred spin axis. The new study carried out by Longo and colleagues found an excess of counter-clockwise rotating or "left-handed" spiral galaxies, compared to their right-handed counterparts. This, they claim, provides evidence that the universe does not have mirror symmetry

The universe was born spinning and continues to do so around a preferred axis – that is the bold conclusion of physicists in the US who have studied the rotation of more than 15,000 galaxies. While most cosmological theories have suggested that – on a large scale – the universe is the same in every direction, these recent findings suggest that the early universe was born spinning about a specific axis. If correct, this also means that the universe does not possess mirror symmetry, but rather has a preferred right or left “handedness”.

Led by Michael Longo from the University of Michigan, the team had set out to test whether mirror symmetry, also referred to as “parity”, was violated on the largest scales. If a particle violates parity, its mirror image would behave differently, and such particles can be described as right- or left-handed. Parity is violated in nuclear beta decays and there is a strong preference in nature for left-handed amino acids, rather than right-handed…. Read the rest of this entry »

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July 26, 2011 at 8:06 am

Posted in ASTRONOMY, COSMOLOGY

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