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Exploding Stars
Speaking today (Friday) at the RAS National Astronomy Meeting at Leicester, Professor Mike Bode of Liverpool John Moores University and Dr Tim O'Brien of Jodrell Bank Observatory will present the latest results which are shedding new light on what happens when stars explode. RS Oph is just over 5,000 light years away from Earth. It consists of a white dwarf star (the super-dense core of a star, about the size of the Earth, that has reached the end of its main hydrogen-burning phase of evolution and shed its outer layers) in close orbit with a much larger red giant star. The two stars are so close together that hydrogen-rich gas from the outer layers of the red giant is continuously pulled onto the dwarf by its high gravity. After around 20 years, enough gas has been accreted that a runaway thermonuclear explosion occurs on the white dwarf's surface. In less than a day, its energy output increases to over 100,000 times that of the Sun, and the accreted gas (several times the mass of the Earth) is ejected into space at......... Posted by: Brooke Permalink Source Interstellar Chemical Tamed in The Lab
Interstellar molecules in a bottle at UCR
The finding of their paper, titled Cyclopropenylidenes: From Interstellar Space to an Isolated Derivative in the Laboratory are being released recently in Science Express a precursor to its publication in the journal Science. The co-authors are Vincent Lavallo, Yves Canac and Bruno Donnadieu who work in the laboratory of Distinguished Professor of Chemistry Guy Bertrand at UCR; and Chemistry Professor Wolfgang W. Schoeller of Gera number of's Universität Bielefeld. "This is about a compound that is very abundant in deep space, which was supposed to not be able to exist in the laboratory, and we found a way to slightly modify it and make it stable," said Bertrand. The new molecule belongs to a family of compounds known as carbenes, very few of which are stable. However, carbenes are now widely used to prepare catalysts that have a number of applications in industries such as pharmaceuticals, plastics and other petrochemicals. The cyclopropenylidene that exists naturally in space is made of three carbon atoms arranged in a triangle with two hydrogen atoms attached. The UCR scientists synthesized a more stable version by replacing the hydrogen with two nitrogen atoms. Because of its unique shape and size, the new carbene prepared at UCR might lead to even more powerful catalysts......... Posted by: Sarah Permalink Source Lunar Rocks Suggest Meteorite Shower
The idea that meteorites have hammered the moon's surface isn't news to scientists. The lunar surface is pock-marked with large craters carved out by the impact of crashing asteroids and meteorites, said Robert Duncan, a professor and associate dean in the College of Oceanic and Atmospheric Sciences at Oregon State University. But the narrow range of the impact dates suggests to scientists that a large spike in meteorite activity took place during a 100-million year interval - possibly the result of collisions in the asteroid belt with comets coming from just beyond our solar system. Results of the study are being published in Geochimica et Cosmochimica Acta, the journal of the international Meteoritical Society. Co-authors with Duncan are Marc Norman of the Australian National University and John Huard, also an oceanographer at OSU. The study was funded by NASA. Tiny melted fragments from the lunar rocks were dated at the noble gas geochronology laboratory at Oregon State. Duncan and Huard were able to use radiometric dating techniques to determine when the rocks had melted after being struck by meteorites. What is especially intriguing, Duncan says, is that this apparent spike in meteorite activity took place about 3.8 to 4 billion years ago - an era that roughly coincides with when researchers believe life first began on Earth, as evidenced by the fossil record of primitive one-cell bacteria......... Posted by: Brooke Permalink Source Nature Can Help Reduce Greenhouse Gas
The authors, including Bruce Hungate of Northern Arizona University and lead author Kees-Jan van Groenigen of UC Davis, discovered that plants are limited in their impact on global warming because of their dependence on nitrogen and other trace elements. These elements are essential to photosynthesis, whereby plants remove carbon dioxide, a greenhouse gas, from the air and transfer carbon back into the soil. "What our paper shows is that in order for soils to lock away more carbon as carbon dioxide rises, there has to be quite a bit of extra nitrogen available--far more than what is normally available in most ecosystems," said Hungate of NAU's Merriam-Powell Center for Environmental Research. The paper notes that various plants can pump nitrogen from the air into soils, and some scientists expected rising carbon dioxide to speed up this natural nitrogen pump, providing the nitrogen needed to store soil carbon. However, the research team found that this process, called nitrogen fixation, cannot keep up with increasing carbon dioxide unless other essential nutrients, such as potassium, phosphorus and molybdenum, are added as fertilizers......... Posted by: Brooke Permalink Source Happy Face On MarsThese images, taken by the High Resolution Stereo Camera (HRSC) on board ESA's Mars Express spacecraft, show the Galle Crater, an impact crater located on the eastern rim of the Argyre Planitia impact basin on Mars.The HRSC obtained these images during orbits 445, 2383, 2438, 2460 and 2493 with a ground resolution ranging between 10-20 metres per pixel, depending on location within the image strip. The images show Crater Galle lying to the east of the Argyre Planitia impact basin and south west of the Wirtz and Helmholtz craters, at 51 degree South and 329 degree East. The images of the 230 km diameter impact crater are mosaics created from five individual HRSC nadir and colour strips, each tens of kilometres wide. A large stack of layered sediments forms an outcrop in the southern part of the crater. Several parallel gullies, possible evidence for liquid water on the Martian surface, originate at the inner crater walls of the southern rim. Crater Galle, named after the German astronomer J.G. Galle (1812-1910), is informally known as the 'happy face' crater. The 'face' was first pointed out in images taken during NASA's Viking Orbiter 1 mission. Its interior shows a surface which is shaped by 'aeolian' (wind-caused) activity as seen in numerous dunes and dark dust devil tracks which removed the bright dusty surface coating......... Posted by: Brooke Permalink Source View Of Earth From Space: Iceberg
This animation, comprised of images acquired by Envisat's Advanced Synthetic Aperture Radar (ASAR), shows the iceberg and the ice tongue before and after the collision. On 26 March, C-16 was pinned at the southern edge of the ice tongue but had started migrating by 27 March. The collision on 30 March shows the ice tongue breaking off, and the final image on 1 April captures C-16 and the new iceberg swinging to the other side of the ice tongue. Mark Drinkwater of ESA's Ocean and Ice Unit said: "During its passage to the coastal foot of the Drygalski Ice Tongue, C-16, which measures 18.5 kilometres by 55 kilometres, looped into and around McMurdo Sound before being carried quickly to the north. "The surface ocean currents appear to have predominantly steered the iceberg, not the winds, thus telling us about important aspects of the adjustment in the ocean circulation since the departure of large grounded icebergs off Ross Island." The floating Drygalski Ice Tongue, which protrudes 80 kilometres into the ocean, is connected to the David Glacier. If it were to break loose, researchers fear it could alter ocean currents and change the region's climate......... Posted by: Brooke Permalink Source "A" ring contains more debris
Caption: The image is a false-color ultraviolet view of Saturn's B ring (center) and A ring (right), separated by a large gap known as the Cassini Division and showing a bright horizontal streak created by a series of time-lapse images involving the star, 26 Taurus. The image was made over a nine-hour period as the star drifted behind the rings. The opacity of the outer A ring is most pronounced on its inner edge, indicating more ring debris is present there. The Encke Gap, much smaller than the Cassini Division, is visible near the outer edge of the A ring. The B ring is significantly more opaque than the A ring, indicating a greater density of ring material when imaged from above. The sky behind the rings glows red in the UV wavelengths from the hydrogen gas that fills the solar system. The images were processed by a CU-Boulder team from data taken by the UVIS instrument aboard the Cassini spacecraft in May 2005.
Credit: NASA/JPL/University of Colorado Prior observations with the Voyager spacecraft in the early part of 1980s found the ring was more transparent, indicating less material, said Joshua Colwell of CU-Boulder's Laboratory for Atmospheric and Space Physics. But new calculations based on May 2005 observations with Cassini's Ultraviolet Imaging Spectrograph, or UVIS, indicates the opacity of the ring is up to 35 percent higher than previously reported. Because of the uneven distribution of the ring particles - which range in size from dust grains to school buses - the transparency of the rings depends on the angle from which they are viewed, he said. The particles are arranged essentially parallel in long stringy clumps as large as 60 feet across, 16 feet thick and 160 feet long, as per models produced from observation data, said Colwell. A paper on the subject by Colwell, Larry Esposito and Miodrag Sremcevic of CU-Boulder's LASP appears in the April 1 issue of Geophysical Research Letters, or GRL. Esposito is science team leader for UVIS, a $12.5 million instrument designed and built at CU-Boulder by LASP that is riding on the Cassini spacecraft......... Posted by: Brooke Permalink Source More Evidence Chicxulub Was Too Early
The Chixculub Impact is suspected to be responsible for the mass extinction of many floral and faunal species, including the large dinosaurs, that marked the end of the Cretaceous period.Image courtesy of www.wa.gov.au A careful geochemical fingerprinting of glass spherules found in multiple layers of sediments from northeast Mexico, Texas, Guatemala, Belize and Haiti all point back to Chicxulub as their source. But the analysis places the impact at about 300,000 years before the infamous extinctions that mark the boundary between the Cretaceous and Tertiary periods, a.k.a. the K-T boundary. Using an array of electron microscopy techniques, Markus Harting of the University of Utrecht in the Netherlands has found that chemical compositions of the spherules all match what would be expected of rocks melted at the Chicxulub impact. The spherules are now found in several layers because after they originally hit the ground, they were "reworked" by erosion to create later layers of sediments, he said. It's this reworking long after the impact that has misplaced some of the spherules into sediments that, based on the fossils in the same sediments, are misleadingly close to the K-T boundary. Harting is scheduled to present his latest findings on Monday, 3 April Backbone of the Americas-Patagonia to Alaska. The meeting is co-convened by the Geological Society of America and the Asociacion Geologica Argentina, with collaboration of the Sociedad Geologica de Chile. The meeting takes place 3-7 April in Mendoza, Argentina......... Posted by: William Permalink Source Understanding Sun's Corona
"It was even more fabulous than we expected," said Jay Pasachoff, professor of astronomy at Williams College (in Williamstown, Mass.) who observed his 42nd solar eclipse. "All the technical equipment worked perfectly, the corona shone brightly, and the activity around sunspots on the eastern edge of the Sun provided an even more dramatic show than predicted." Chair of the International Astronomical Union's Working Group on Eclipses, Pasachoff led an expedition of dozens of researchers and students to record images from the rare, three-minute event. They are capturing data over a number of eclipses to understand better why the Sun's corona, the outer halo of million-degree gas, shines hotter than the Sun itself. Most of the corona is visible from Earth only for the fleeting time that the Moon totally blocks the Sun's direct rays. Tourists and residents, who had packed the tiny island's harbor-side, cheered at the appearance of the "diamond ring" effect that brought the total eclipse to a close while ships blew their horns in celebration. Two of the group's experiments involved taking rapid series of images, ten times per second, with new electronic cameras through specially designed filters. One filter passes a narrowly defined color in the green portion of the light spectrum and the other passes a narrowly defined color in the red......... Posted by: Brooke Permalink Source Football-field Sized Moonlets In Saturn's A Ring
New observations of propeller-shaped disturbances in Saturn's A ring indicate the presence of four small, embedded moons -- and most likely millions more, Cornell University astronomers report. This is the first evidence of the existence of moonlets bridging the gap in size between the larger ring moons Pan and Daphnis (several miles each in diameter) and the much smaller ice particles that comprise the bulk of the rings. The discovery could lead to a better understanding of the origin and formation of Saturn's rings and the solar system as a whole. Matthew Tiscareno, a Cornell research associate, is lead author of a paper describing the discovery in the March 30 issue of the journal Nature. The four disturbances, which appear as pairs of slightly offset bright horizontal streaks in an otherwise bland region of the ring, were captured in two images taken in 2004 by NASA's Cassini spacecraft. Astronomers say the streaks are indicators of orbiting moons about 100 meters (328 feet) in diameter: about the length of a football field, but still too small for even Cassini's highly sensitive Imaging Science Subsystem (ISS) to see directly, but large enough to exert an observable gravitational pull on the particles around them. "The discovery of these intermediate-sized particles tells us that Pan and Daphnis are probably just the largest members of the ring population, rather than interlopers from somewhere else," said Tiscareno......... Posted by: Brooke Permalink Source |
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