New Kind Of Astronomical Object Around Black Hole: Living Fossil

The tight cluster of stars surrounding a supermassive black hole after it has been violently kicked out of a galaxy represents a new kind of astronomical object and a fossil record of the kick.

A paper published in the July 10 in sciencedaily.com issue of The Astrophysical Journal discusses the theoretical properties of “hypercompact stellar systems” and suggests that hundreds of these faint star clusters might be detected at optical wavelengths in our immediate cosmic environment. Some of these objects may already have been picked up in astronomical surveys, reports David Merritt, from Rochester Institute of Technology, Jeremy Schnittman, from Johns Hopkins University, and Stefanie Komossa, from the Max-Planck-Institut for Extraterrestrial Physics in Germany.

Hypercompact stellar systems result when a supermassive black hole is violently ejected from a galaxy, following a merger with another supermassive black hole. The evicted black hole rips stars from the galaxy as it is thrown out. The stars closest to the black hole move in tandem with the massive object and become a permanent record of the velocity at which the kick occurred.

“You can measure how big the kick was by measuring how fast the stars are moving around the black hole,” says Merritt, professor of physics at RIT. “Only stars orbiting faster than the kick velocity remain attached to the black hole after the kick. These stars carry with them a kind of fossil record of the kick, even after the black hole has slowed down. In principle, you can reconstruct the properties of the kick, which is nice because there would be no other way to do it.”

“Finding these objects would be like discovering DNA from a long-extinct species,” adds Komossa.

The best place to find hypercompact stellar systems, the authors argued, is in cluster of galaxies like the nearby Coma and Virgo clusters. These dense regions of space contain thousands of galaxies that have been merging for a long time. Merging galaxies result in merging black holes, which is a prerequisite for the kicks.

“Even if the black hole gets kicked out of one galaxy, it’s still going to be gravitationally bound to the whole cluster of galaxies,” Merritt says. “The total gravity of all the galaxies is acting on that black hole. If it was ever produced, it’s still going to be there somewhere in that cluster.”

Merritt and his co-authors think that scientists may have already seen hypercompact stellar systems and not realized it. These objects would be easy to mistake for common star systems like globular clusters. The key signature making hypercompact stellar systems unique is a high internal velocity. This is detectable only by measuring the velocities of stars moving around the black hole, a difficult measurement that would require a long time exposure on a large telescope.

From time to time, a hypercompact stellar system will make its presence known in a much more dramatic way, when one of the stars is tidally disrupted by the supermassive black hole. In this case, gravity stretches the star and sucks it into the black hole. The star is torn apart, causing a beacon-like flare that signals a black hole. The possibility of detecting one of these “recoil flares” was first discussed in an August 2008 paper by co-authors Merritt and Komossa.

“The only contact of these floating black holes with the rest of the universe is through their armada of stars,” Merritt says, “with an occasional display of stellar fireworks to signal ‘here we are.’”

Window collects light and illuminates room !!

Imagine windows that not only provide a clear view and illuminate rooms, but also efficiently help power the building. MIT engineers report a new approach to harnessing the sun's energy that could allow just that.

The work involves creating a ‘solar concentrator’.

"Light is collected over a large area [like a window] and gathered or concentrated, at the edges," explains Marc A Baldo, leader of the work and the Esther and Harold E Edgerton Career Development Associate Professor of Electrical Engineering.

As a result, rather than covering a roof with solar cells, the cells only need to be around the edges of a flat glass panel. In addition, the focused light increases the electrical power obtained from each solar cell "by a factor of over 40," Baldo says.

Because the system is simple to manufacture, the team believes that it could be implemented within three years — even added onto existing solar-panel systems to increase their efficiency by 50%.

In addition to Baldo, the researchers involved are Michael Currie, Jon Mapel and Timothy Heidel, all graduate students in the Department of Electrical Engineering and Computer Science, and Shalom Goffri, a postdoctoral associate in MIT's Research Laboratory of Electronics.

"Professor Baldo's project uses design to achieve superior solar conversion without optical tracking," says Dr Aravinda Kini, program manager in the Office of Basic Energy Sciences in the US Department of Energy's Office of Science, a sponsor of the work.

"This accomplishment demonstrates the importance of innovative basic research in bringing about advances in solar energy use."

Solar concentrators in use today "track the sun to generate high optical intensities, often by using large mobile mirrors that are expensive to deploy and maintain," Baldo says. Solar cells at the focal point of the mirrors must be cooled and the entire assembly wastes space around the perimeter to avoid shadowing neighbouring concentrators.

The concentrator is a mixture of two or more dyes, painted onto a pane of glass or plastic. The dyes work together to absorb light across a range of wavelengths, which is then re-emitted at a different wavelength and transported across the pane to waiting solar cells at the edges.

In the 1970s, similar solar concentrators were developed by impregnating dyes in plastic. But the idea was abandoned because, among other things, not enough of the collected light could reach the edges of the concentrator as much of it was lost en route.

The MIT engineers, experts in optical techniques developed for lasers and organic light-emitting diodes, realised that perhaps those same advances could be applied to solar concentrators. The result? A mixture of dyes in specific ratios, applied only to the surface of the glass, that allows some level of control over light absorption and emission.

"We made it so the light can travel a much longer distance," Mapel said.

"We were able to substantially reduce light transport losses, resulting in a tenfold increase in the amount of power converted by the solar cells."

Source: www.electroline.com

Converting Sunlight Into Electricity: European Project Breaks Efficiency Record

Scientists of the Commission-financed project FULLSPECTRUM have developed photovoltaic (PV) multi-junction (MJ) solar cells which are able to convert 39.7% of the energy of sun light into electricity. This is the highest percentage ever reached in Europe, according to researchers after their final workshop in El Escorial, Spain.
The main barrier to large-scale deployment of PV systems is the high production cost of electricity, due to the significant capital investment costs. Research is engaged to reduce manufacturing costs and to raise the efficiency of the cells. Today conventional PV cells made of silicon are converting only a fraction of the solar light spectrum around 17%.
FULLSPECTRUM's multi-junction solar cells are able to catch more sun light energy due to their composition of different materials, including gallium, phosphorus, indium and germanium. These multi-junction solar cells are expensive and have only been used for applications in space. However, the cost can be considerably reduced by arranging them in special panels which include lenses that focus a large amount of solar energy onto the cells. These concentrators can reach far above 1000 times the natural solar power flux and have also been the object of the project research.
FULLSPECTRUM is an integrated project involving 19 European public and industrial research centres from seven EU Member States, as well as Russia and Switzerland. It is coordinated by the Universidad Politécnica de Madrid, Instituto de Energía Solar and started in November 2003 with an overall budget of € 14,7 Million of with the European Commission financed € 8.4 Million.
From: Sciencedaily.com

New Power Line De-icing System Developed

ScienceDaily (Jan. 9, 2009)
The new proprietary technology is called a variable resistance cable (VRC) de-icing system. With only minor cable modifications plus some off-the-shelf electronics, the system switches the electrical resistance of a standard power line from low to high. The high resistance automatically creates heat to melt ice build-up or keep it from forming in the first place.
"The beauty of the VRC system is that it's fully customizable and is an affordable addition to the current manufacturing and installation process," said Gabriel Martinez, Ice Engineering's Vice President who studied under Professor Petrenko while earning his M.S. in engineering sciences from Dartmouth. "And it works without causing any service interruption whatsoever," he added.
"The technology builds on many years of research in materials science, power electronics, and ice physics with my colleagues at Dartmouth such as Professor Charles Sullivan, an expert in power electronics and a co-inventor of the VRC de-icer," said Petrenko who is founder, Chief Technology Officer and Chairman of the Board of Ice Engineering.
Ice Engineering plans to install and test a full-scale VRC system prototype on a section of power line in Orenburg, Russia, in late January 2009. The company is also currently negotiating full-scale installations of VRC in other regions of Russia and in China.
Martinez says the changes in manufacturing and installation required to implement the VRC system would result in a less than 10 percent increase in overall cost. Since utility companies normally replace 3 percent of their cables every year, the system could be installed as part of the regularly scheduled maintenance process and still achieve a significant portion of the installation by the time the next major storm hits.
Furthermore, the life span of the de-icing system would match or exceed the life-span of the utility cable, approximately 30–50 years. The system would pay for itself during the next storm by practically eliminating the cost of fixing downed cables and power outages due to ice and snow, according to Martinez.
Another benefit to the VRC system is that utility companies using the system would have full control over its functionality, says Martinez. Time, temperature, and location can all be adjusted manually or set and controlled automatically with electronic sensors.
Ice Engineering in Lebanon, N.H. develops and licenses technology and applications that enable products that interact with ice and snow to perform significantly better than ever before. Dartmouth engineering professor Victor Petrenko is the primary inventor of the technology. Ice Engineering was founded by Petrenko as a Delaware LLC in April of 2001 to commercialize the technology in specific industries.

New Plasma Transistor Could Create Sharper Displays

By integrating a solid-state electron emitter and a microcavity plasma device, researchers at the University of Illinois have created a plasma transistor that could be used to make lighter, less expensive and higher resolution flat-panel displays.
"The new device is capable of controlling both the plasma conduction current and the light emission with an emitter voltage of 5 volts or less," said Gary Eden, a professor of electrical and computer engineering, and director of the Laboratory for Optical Physics and Engineering at the U. of I.
At the heart of the plasma transistor is a microcavity plasma, an electronic-photonic device in which an electrically charged gas (a plasma) is contained within a microscopic cavity. Power is supplied by two electrodes at voltages of up to 200 volts.
Eden and graduate student Kuo-Feng (Kevin) Chen fabricated the plasma transistor from copper-clad laminate into which a microcavity 500 microns in diameter was produced by standard photolithographic techniques. The solid-state electron emitter was made from a silicon wafer, topped with a thin layer of silicon dioxide.
The microcavity is approximately the diameter of a human hair, and is filled with a small amount of gas. When excited by electrons, atoms in the plasma radiate light. The color of light depends on what gas is placed in the microcavity. Neon emits red light, for example, and argon emits blue light.
Around the plasma is a thin boundary layer called the sheath. Within the sheath, electrical current is carried not by negatively charged electrons, but instead by positively charged ions. Much heavier than electrons and therefore harder to accelerate, the ions require a large electric field generated by a large voltage drop across the sheath.
The intense electric field within the plasma sheath also promotes electron transport, said Eden, who also is a researcher at the university's Coordinated Science Laboratory and at the Micro and Nanotechnology Laboratory. "By injecting electrons from the emitter into the sheath, we can significantly increase the flow of electrons through the plasma, which increases the plasma's conductivity and light emission."
While the microcavity plasma still requires up to 200 volts to emit light and conduct current, the current and light emission can be controlled by an electron emitter operating at 5 volts or less, Eden said. The current that is sent through the sheath to the bulk plasma determines how much current is carried by the two electrodes driving the microplasma.
In previous work, Eden's team created flat-panel plasma lamps out of two sheets of aluminum foil separated by a thin dielectric layer of clear aluminum oxide. More than 250,000 lamps can be packed into a single panel. And, because microcavity plasmas operate at atmospheric pressure, thick pieces of glass are not needed to seal them. The lightweight plasma panels are less than 1 millimeter thick.
"Being able to control each microcavity plasma independently could turn our plasma panel into a less expensive and higher resolution plasma display," Eden said. "The plasma transistor also could be used in applications where you want to use a small voltage to control a great deal of power."
Eden and Chen described the plasma transistor in the journal Applied Physics Letters. The researchers have applied for a patent.
courtesy: scincedaily.com