Silicates
Silicates have been observed in space, around evolved stars and planetary nebulae such as NGC 6302. They are found in both amorphous form and crystalline form, though the range of types that have been found is far smaller than those found on Earth.
A silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. This definition is broad enough to include species such as hexafluorosilicate ("fluorosilicate"), [SiF6]2?, but the silicate species that are encountered most often consist of silicon with oxygen as the ligand. Silicate anions, with a negative net electrical charge, must have that charge balanced by other cations to make an electrically neutral compound.
Silica, or silicon dioxide, SiO2, is sometimes considered a silicate, although it is the special case with no negative charge and no need for counter-ions. Silica is found in nature as the mineral quartz, and its polymorphs.
Wikipedia - Silicates (http://en.wikipedia.org/wiki/Silicates)
Sand - silica - Silicon dioxide
The chemical compound silicon dioxide, also known as silica ... Silica is most commonly found in nature as sand or quartz, as well as in the cell walls of diatoms. It is a principal component of most types of glass and substances such as concrete. Silica is the most abundant mineral in the earth's crust.
Wikipedia - Sand - Silica - Silicon dioxide (http://en.wikipedia.org/wiki/Silicates)
Forsterite is destroyed quickly in normal galaxies by radiation, so it must be continually produced to be detected by Spitzer.
NASA
This plot of data captured by NASA's Spitzer Space Telescope reveals dust entrained in the winds rushing away from a quasar, or growing black hole. The quasar, called PG2112+059, is located deep inside a galaxy 8 billion light-years away. Astronomers believe the dust might have been forged in the winds, which would help explain where dust in the very early universe came from.
The data were captured by Spitzer's infrared spectrograph, an instrument that splits apart light from the quasar into a spectrum that reveals telltale signs of different minerals. Each type of mineral, or dust grain, has a unique signature, as can be seen in the graph, or spectrum, above.
The strongest features are from the mineral amorphous olivine, or glass (purple); the mineral forsterite found in sand (blue); and the mineral corundum found in rubies (light blue). The detection of forsterite and corundum is highly unusual in galaxies without quasars. Therefore, their presence is a key clue that these grains might have been created in the quasar winds and not by dying stars as they are in our Milky Way galaxy. Forsterite is destroyed quickly in normal galaxies by radiation, so it must be continually produced to be detected by Spitzer.
Corundum is hard, and provides a seed that softer, more common minerals usually cover up. As a result, corundum is usually not seen in spectra of galaxies. Since Spitzer did detect the mineral, it is probably forming in a clumpy environment, which is expected in quasar winds. All together, the signatures of the unusual minerals in this spectrum point towards dust grains forming in the winds blowing away from quasars.
NASA's Spitzer Space Telescope (http://www.spitzer.caltech.edu/Media/releases/ssc2007-16/ssc2007-16a.shtml)
Black hole spews water vapour
The vapour is thought to be present in a jet ejected from a supermassive black hole at the centre of a galaxy that is billions of light-years away.
The vapour is observed as a "maser", in which molecules in the gas amplify and emit beams of microwave radiation.
"We have been observing the water maser every month since the detection and seen a steady signal with no apparent change in the velocity of the water vapour in the data we've obtained so far," said Dr John McKean of the Netherlands Institute for Radio Astronomy.
"This backs up our prediction that the water is found in the jet from the supermassive black hole, rather than the rotating disc of gas that surrounds it."
The researchers said it was likely there were many more galaxies like this one in the early Universe. But surveys of nearby - and hence younger - galaxies show that only about 5% have powerful water masers associated with active galactic nuclei.
In addition, studies show that very powerful water masers are extremely rare compared with their less luminous counterparts. "We found a signal from a really powerful water maser in the first system that we looked at using the gravitational lensing technique," said Dr McKean.
If these phenomena were just as rare in the early Universe as they are today, he said, the chances of detecting one would have been vanishingly small - about one in a million, in fact.
"This means that the abundance of powerful water masers must be much higher in the distant Universe than found locally because I'm sure we are just not that lucky," he added.
BBC News (http://news.bbc.co.uk/2/hi/science/nature/8012501.stm)
Water found on the sun
WATERLOO, Ont. - Water has been discovered on the surface of the sun in sunspots where it causes a sort of "stellar greenhouse effect" that affects the sunspot's energy output.
"There's a perception that the sun is too hot to form water on its surface, but we have proved that it exists in sunspots because they are cooler," said Peter Bernath, a chemistry professor at the University of Waterloo.
Scientists from UW and the National Optical Astronomy Observatories in Tucson, Ariz., recorded evidence of water - - not in liquid form because the sun is too hot, but as vapor or steam -- in dark sunspots.
The discovery is of fundamental importance for understanding the atmospheres of the sun and stars. Hot water molecules are the most important absorbers of infrared radiation in the atmospheres of cool stars, such as "variable red giants." Studying the physical effects of hot water in these red giant stars may be central to determining the rate at which they evolve and eject material into space.
Dark sunspots can be 2,000 degrees C cooler than the surrounding bright surface of the sun, allowing detailed studies of regions that mimic the surfaces of red giant stars. Sunspots are caused by magnetic fields that float to the surface of the sun and locally suppress energy flow from the core.
Bernath, an expert in molecular astronomy, said it is surprising to find water vapor on the sun because its surface temperature of 5,700 degrees C causes it to break into atoms of hydrogen and oxygen. Since sunspots are cooler, the atoms can recombine to form water vapor that can absorb escaping infrared radiation.
"This formation of water vapor affects the energy flow from sunspots, creating a kind of stellar greenhouse effect," he said. Bernath believes, however, this has no effect on climate on earth.
Astronomers Lloyd Wallace, William Livingston and Kenneth Hinkle of the Arizona-based observatories worked with collaborators to obtain infrared spectra that reveal a large number of water absorption features originating on the sun.
The lab research, in which the team recorded an infrared emission spectrum of hot water at 1,550 degrees C, supported the results obtained from the telescope measurements. By comparing the lab spectrum with the sunspot spectrum, it proved for the first time that hot water vapor is present on the sun, Bernath said.
"Since the temperatures of cool stars are very difficult to produce in the laboratory, these results are unique and show that current theory is not adequate to model these spectra and that a basic understanding of the behavior of water must be explored further by scientists," he said.
Bernath said the spectrum of hot water is also important here on earth. "For example, the exhaust of a rocket contains hot water vapor. This rocket plume provides a signature that can be used to identify the type of rocket. The spectrum of water also serves as a continuing challenge to theoreticians. New theoretical techniques in spectroscopy are often tested using the water spectrum."
University of Waterloo News Bureau (http://newsrelease.uwaterloo.ca/news.php?id=396)
NASA's Spitzer Space Telescope has discovered an enormous ring around Saturn -- by far the largest of the giant planet's many rings.
The new belt lies at the far reaches of the Saturnian system, with an orbit tilted 27 degrees from the main ring plane. The bulk of its material starts about six million kilometers (3.7 million miles) away from the planet and extends outward roughly another 12 million kilometers (7.4 million miles). One of Saturn's farthest moons, Phoebe, circles within the newfound ring, and is likely the source of its material.
Saturn's newest halo is thick, too -- its vertical height is about 20 times the diameter of the planet. It would take about one billion Earths stacked together to fill the ring.
NASA's Spitzer Space Telescope Discovers Largest Ring Around Saturn - sciencedaily .com (http://www.sciencedaily.com/releases/2009/10/091006205610.htm)
The discovery may help solve an age-old riddle of one of Saturn's moons. Iapetus has a strange appearance -- one side is bright and the other is really dark, in a pattern that resembles the yin-yang symbol...
Saturn's newest addition could explain how Cassini Regio came to be. The ring is circling in the same direction as Phoebe, while Iapetus, the other rings and most of Saturn's moons are all going the opposite way. According to the scientists, some of the dark and dusty material from the outer ring moves inward toward Iapetus, slamming the icy moon like bugs on a windshield.
"Astronomers have long suspected that there is a connection between Saturn's outer moon Phoebe and the dark material on Iapetus," said Hamilton. "This new ring provides convincing evidence of that relationship."
NASA's Spitzer Space Telescope Discovers Largest Ring Around Saturn - sciencedaily .com (http://www.sciencedaily.com/releases/2009/10/091006205610.htm)
NASA: Studies of two supernova remnants using the Japan-U.S. Suzaku observatory have revealed never-before-seen embers of the high-temperature fireballs that immediately followed the explosions. Even after thousands of years, gas within these stellar wrecks retain the imprint of temperatures 10,000 times hotter than the sun's surface.
"This is the first evidence of a new type of supernova remnant -- one that was heated right after the explosion," said Hiroya Yamaguchi at the Institute of Physical and Chemical Research in Japan.
A supernova remnant usually cools quickly due to rapid expansion following the explosion. Then, as it sweeps up tenuous interstellar gas over thousands of years, the remnant gradually heats up again.
Capitalizing on the sensitivity of the Suzaku satellite, a team led by Yamaguchi and Midori Ozawa, a graduate student at Kyoto University, detected unusual features in the X-ray spectrum of IC 443, better known to amateur astronomers as the Jellyfish Nebula.
The remnant, which lies some 5,000 light-years away in the constellation Gemini, formed about 4,000 years ago. The X-ray emission forms a roughly circular patch in the northern part of the visible nebulosity.
Suzaku's X-ray Imaging Spectrometers (XISs) separate X-rays by energy in much the same way as a prism separates light into a rainbow of colors. This allows astronomers to tease out the types of processes responsible for the radiation.
Some of the X-ray emission in the Jellyfish Nebula arises as fast-moving free electrons sweep near the nuclei of atoms. Their mutual attraction deflects the electrons, which then emit X-rays as they change course. The electrons have energies corresponding to a temperature of about 12 million degrees Fahrenheit (7 million degrees Celsius).
Several bumps in the Suzaku spectrum were more puzzling. "These structures indicate the presence of a large amount of silicon and sulfur atoms from which all electrons have been stripped away," Yamaguchi said. These "naked" nuclei produce X-rays as they recapture their lost electrons.
But removing all electrons from a silicon atom requires temperatures higher than about 30 million degrees F (17 million C); hotter still for sulfur atoms. "These ions cannot form in the present-day remnant," Yamaguchi explained. "Instead, we're seeing ions created by the enormous temperatures that immediately followed the supernova."
The team suggests that the supernova occurred in a relatively dense environment, perhaps in a cocoon of the star's own making. As a massive star ages, it sheds material in the form of an outflow called a stellar wind and creates a cocoon of gas and dust. When the star explodes, the blast wave traverses the dense cocoon and heats it to temperatures as high as 100 million degrees F (55 million C), or 10,000 times hotter than the sun's surface.
Eventually, the shock wave breaks out into true interstellar space, where the gas density can be as low as a single atom per cubic centimeter -- about the volume of a sugar cube. Once in this low-density environment, the young supernova remnant rapidly expands.
The expansion cools the electrons, but it also thins the remnant's gas so much that collisions between particles become rare events. Because an atom may take thousands of years to recapture an electron, the Jellyfish Nebula's hottest ions remain even today, the astronomers reported in the Nov. 1 issue of The Astrophysical Journal.
"Suzaku sees the Jellyfish's hot heart," Ozawa said.
The team has already identified another fossil fireball in the supernova remnant known as W49B, which lies 35,000 light-years away in the constellation Aquila. In the Nov. 20 edition of The Astrophysical Journal, Ozawa, Yamaguchi and colleagues report X-ray emission from iron atoms that are almost completely stripped of electrons. Forming these ions requires temperatures in excess of 55 million degrees F (30 million C)-- nearly twice the observed temperature of the remnant's electrons.
Suzaku finds 'fossil' fireballs from supernovae - onorbit .com (http://www.onorbit.com/node/1877)
...W49B is a barrel-shaped nebula located about 35,000 light years from Earth. The new data reveal bright infrared rings, like hoops around a barrel, and intense X-radiation from iron and nickel along the axis of the barrel.
"These results provide intriguing evidence that an extremely massive star exploded in two powerful, oppositely directed jets that were rich in iron," said Jonathan Keohane of NASA's Jet Propulsion Laboratory at a press conference at the American Astronomical Society meeting in Denver.
...According to the collapsar theory, gamma-ray bursts are produced when a massive star runs out of nuclear fuel and the star's core collapses to form a black hole surrounded by a disk of extremely hot, rapidly rotating, magnetized gas. Much of this gas is pulled into the black hole, but some is flung away in oppositely directed jets of gas traveling at near the speed of light.
...Chandra's image and spectral data show that the jets of multimillion-degree-Celsius gas extending along the axis of the barrel are rich in iron and nickel ions, consistent with their being ejected from the center of the star. This distinguishes the explosion from a conventional type II supernova in which most of the Fe and Ni goes into making the neutron star, and the outer part of the star is what is flung out. In contrast, in the collapsar model of gamma ray bursts iron and nickel from the center is ejected along the jet.
At the ends of the barrel, the X-ray emission flares out to make a hot cap. The X-ray cap is surrounded by a flattened cloud of hydrogen molecules detected in the infrared. These features indicate that the shock wave produced by the explosion has encountered a large, dense cloud of gas and dust.
...The observations of W49B may help to resolve a problem that has bedeviled the collapsar model for gamma-ray bursts. On the one hand, the model is based on the collapse of a massive star, which is normally formed from a dense cloud. On the other hand, observations of the afterglow of many gamma-ray bursts indicate that the explosion occurred in a low-density gas...
NASA Chandra Observation of Supernova W49B Supernova Points to Ancient Gamma Ray Burst - spaceref .com (http://www.spaceref.com/news/viewpr.html?pid=14325)
Explosive nucleosynthesis and stellar explosions. The rest W49B
The study of supernova remnants can obtain information on the mechanisms of supernova explosions and the processes of explosive nucleosynthesis...
In the context of a collaboration with DSM / DAPNIA / Service d'Astrophysique of CEA Saclay has been that we analyzed X-ray observation of W49B obtained with XMM-Newton satellite. The analysis allowed to study the spatial distribution of chemical and physical properties of the ejecta $ $ in this supernova remnant and to obtain important information on the dynamics of the explosion. The spatially resolved spectral analysis results show that W49B is a clear anisotropy of the ejecta in terms of temperature and chemical composition (see Figure 56). In every region of W49B, however, the abundances of Si, S, Ca, Ar, Mg and Fe are sovrasolari and this confirms that we are seeing elements synthesized during the life of the progenitor star and stages of his death (through the phenomenon of explosive nucleosynthesis).
...Note that, assuming aspherical explosion and bipolar, you must consider an anisotropic jet where the eastern arm is significantly longer, warmer and richer in Fe than the West. Note however that the presence of aspherical explosion does not necessarily produce a GRB, which is also required for the release of $ \ sim10 ^ (52) $ erg of energy, or un'hypernova.
To test the possibility that W49B is a remnant of GRBs, we compared the abundances found in the bar $ a $ with the predictions of numerical models of explosive nucleosynthesis in bipolar supernova explosions aspherical and developed by Maeda and Nomoto 2003. In particular, we compared the expected values and those observed (X / Xo) / (Fe / Feo), with X = Si, S, Ar, Ca, Cr, M and Ni. Neither model accurately reproduces the observed abundances...
In conclusion, our analysis showed that the association of W49B with a gamma-ray burst is not supported by clear observational evidence, but there are clear indications of aspherical explosion.
Explosive nucleosynthesis and stellar explosions. The rest W49B - astropa.inaf .it (http://www.astropa.inaf.it/Rapporto_Annuale/DOCOSS2006/HTML/node42.html)