Archive for June 27, 2013

Spiral Galaxies Like Milky Way Bigger Than Thought Says CU-Boulder Study

Image courtesy NASA

Image courtesy NASA

Let’s all fist bump: Spiral galaxies like our own Milky Way appear to be much larger and more massive than previously believed, according to a new University of Colorado Boulder study by researchers using the Hubble Space Telescope.

CU-Boulder Professor John Stocke, study leader, said new observations with Hubble’s $70 million Cosmic Origins Spectrograph, or COS, designed by CU-Boulder show that normal spiral galaxies are surrounded by halos of gas that can extend to over 1 million light-years in diameter. The current estimated diameter of the Milky Way, for example, is about 100,000 light-years. One light-year is roughly 6 trillion miles.

The material for galaxy halos detected by the CU-Boulder team originally was ejected from galaxies by exploding stars known as supernovae, a product of the star formation process, said Stocke of CU-Boulder’s astrophysical and planetary sciences department. “This gas is stored and then recycled through an extended galaxy halo, falling back onto the galaxies to reinvigorate a new generation of star formation,” he said. “In many ways this is the ‘missing link’ in galaxy evolution that we need to understand in detail in order to have a complete picture of the process.”

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Revealed The Mystery Of The Gigantic Storm On Saturn

We now understand the nature of the giant storms on Saturn. Through the analysis of images sent from the Cassini space probe belonging to the North American and European space agencies (NASA and ESA respectively), as well as the computer models of the storms and the examination of the clouds therein, the Planetary Sciences Group of the University of the Basque Country has managed to explain the behaviour of these storms for the very first time. The article explaining the discovery, the lead author being Enrique García Melendo, researcher at the Fundació Observatori Esteve Duran – Institut de Ciències de l’Espai, of Catalonia, was published in Nature Geosciences.

Approximately once every Saturnian year – equivalent to 30 Earth years – an enormous storm is produced on the ringed planet and which affects the aspect of its atmosphere on a global scale. These gigantic storms are known as Great White Spots, due to the appearance they have on the atmosphere of the planet. The first observation of one of these was made in 1876; the Great White Spot of 2010 was the sixth one to be observed. On this occasion the Cassini space vehicle was able to obtain very high resolution images of this great meteorological structure.

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The Violent Birth Of Neutron Stars

A team of researchers at the Max Planck Institute for Astrophysics conducted the most expensive and most elaborate computer simulations so far to study the formation of neutron stars at the center of collapsing stars with unprecedented accuracy. These worldwide first three-dimensional models with a detailed treatment of all important physical effects confirm that extremely violent, hugely asymmetric sloshing and spiral motions occur when the stellar matter falls towards the center. The results of the simulations thus lend support to basic perceptions of the dynamical processes that are involved when a star explodes as supernova.

Stars with more than eight to ten times the mass of our Sun end their lives in a gigantic explosion, in which the stellar gas is expelled into the surrounding space with enormous power. Such supernovae belong to the most energetic and brightest phenomena in the universe and can outshine a whole galaxy for weeks. They are the cosmic origin of chemical elements like carbon, oxygen, silicon, and iron, of which the Earth and our bodies are made of, and which are bred in massive stars over millions of years or freshly fused in the stellar explosion.

Supernovae are also the birth places of neutron stars, those extraordinarily exotic, compact stellar remnants, in which about 1.5 times the mass of our Sun is compressed to a sphere with the diameter of Munich. This happens within fractions of a second when the stellar core implodes due to the strong gravity of its own mass. The catastrophic collapse is stopped only when the density of atomic nuclei – gargantuan 300 million tons in a sugar cube – is exceeded.

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G1.9+0.3: The Remarkable Remains Of A Recent Supernova

Credit: X-ray (NASA/CXC/NCSU/K. Borkowski et al.); Optical (DSS)

Credit: X-ray (NASA/CXC/NCSU/K. Borkowski et al.); Optical (DSS)

Astronomers estimate that a star explodes as a supernova in our Galaxy, on average, about twice per century. In 2008, a team of scientists announced they discovered the remains of a supernova that is the most recent, in Earth’s time frame, known to have occurred in the Milky Way.

The explosion would have been visible from Earth a little more than a hundred years ago if it had not been heavily obscured by dust and gas. Its likely location is about 28,000 light years from Earth near the center of the Milky Way. A long observation equivalent to more than 11 days of observations of its debris field, now known as the supernova remnant G1.9+0.3, with NASA’s Chandra X-ray Observatory is providing new details about this important event.

The source of G1.9+0.3 was most likely a white dwarf star that underwent a thermonuclear detonation and was destroyed after merging with another white dwarf, or pulling material from an orbiting companion star. This is a particular class of supernova explosions (known as Type Ia) that are used as distance indicators in cosmology because they are so consistent in brightness and incredibly luminous.

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First Transiting Planets In A Star Cluster Discovered

All stars begin their lives in groups. Most stars, including our Sun, are born in small, benign groups that quickly fall apart. Others form in huge, dense swarms that survive for billions of years as stellar clusters. Within such rich and dense clusters, stars jostle for room with thousands of neighbors while strong radiation and harsh stellar winds scour interstellar space, stripping planet-forming materials from nearby stars.

It would thus seem an unlikely place to find alien worlds. Yet 3,000 light-years from Earth, in the star cluster NGC 6811, astronomers have found two planets smaller than Neptune orbiting Sun-like stars. The discovery, published in the journal Nature, shows that planets can develop even in crowded clusters jam-packed with stars.

“Old clusters represent a stellar environment much different than the birthplace of the Sun and other planet-hosting field stars,” says lead author Soren Meibom of the Harvard-Smithsonian Center for Astrophysics (CfA). “And we thought maybe planets couldn’t easily form and survive in the stressful environments of dense clusters, in part because for a long time we couldn’t find them.”

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