Novel Devices ♦ news digest Jacques Dordain, ESA’s Director General.
“It is down to the expertise of Europe’s space industry and scientific community that this next-generation mission is now well and truly on its way to making ground-breaking discoveries about our Milky Way.”
Repeatedly scanning the sky, Gaia will observe each of the billion stars an average of 70 times each over the five years. It will measure the position and key physical properties of each star, including its brightness, temperature and chemical composition.
By taking advantage of the slight change in perspective that occurs as Gaia orbits the Sun during a year, it will measure the stars’ distances and, by watching them patiently over the whole mission, their motions across the sky.
The position, motion and properties of each star provide clues about its history, and Gaia’s huge census will allow scientists to piece together a ‘family tree’ for our home Galaxy.
The motions of the stars can be put into ‘rewind’ to learn more about where they came from and how the Milky Way was assembled over billions of years from the merging of smaller galaxies, and into ‘fast forward’ to learn more about its ultimate fate.
“Gaia represents a dream of astronomers throughout history, right back to the pioneering observations of the ancient Greek astronomer Hipparchus, who catalogued the relative positions of around a thousand stars with only naked-eye observations and simple geometry,” says Alvaro Giménez, ESA’s Director of Science and Robotic Exploration.
“Over 2000 years later, Gaia will not only produce an unrivalled stellar census, but along the way has the potential to uncover new asteroids, planets and dying stars.”
By comparing its repeated scans of the sky, Gaia will also discover tens of thousands of supernovas, the death cries of stars as they reach the end of their lives and explode. And slight periodic wobbles in the positions of some stars should reveal the presence of planets in orbit around them, as they tug the stars from side to side.
Gaia will also uncover new asteroids in our Solar System and refine the orbits of those already known, and will make precise tests of Einstein’s famous theory of General Relativity.
After five years, the data archive will exceed 1 Petabyte or 1 million Gigabytes, equivalent to about 200 000 DVD’s worth of data. The task of processing and
analysing this mountain of data will fall to the Gaia Data Processing and Analysis Consortium, comprising more than 400 individuals across at scientific institutes across Europe.
“Where Hipparcos catalogued 120,000 stars, Gaia will survey almost 10,000 times as many and at roughly forty times higher precision,” says Timo Prusti, ESA’s Gaia project scientist.
“Along with tens of thousands of other celestial and planetary objects, this vast treasure trove will give us a new view of our cosmic neighbourhood and its history, allowing us to explore the fundamental properties of our Solar System and the Milky Way, and our place in the wider Universe.”
“After years of hard work and determination of everyone involved in the mission, we are delighted to see our Gaia discovery machine on the road to L2, where we will continue the noble European tradition of star charting to decipher the history of the Milky Way,” adds Giuseppe Sarri, ESA’s Gaia project manager.
The spacecraft was designed and built by Astrium, with a core team composed out of Astrium France, Germany and the United Kingdom.
Tiny Quantum Dots boost charge transfer in solar cells
A single-particle study identifies a possible path to improved conversion of sunlight to electricity in photovoltaic devices and LEDs
Quantum dots - tiny semiconductor crystals with diameters measured in billionths of a metre - have enormous potential for applications that make use of their ability to absorb or emit light and/or electric charges.
Examples include more vividly coloured LEDs, photovoltaic solar cells, nanoscale transistors, and biosensors. But because these applications have differing and sometimes opposite requirements, finding ways to control the dots’ optical and electronic properties is crucial to their success.
In a recent study in the journal Chemical Communications, scientists at the U.S. Department of Energy’s Brookhaven National Laboratory, Stony Brook University, and Syracuse University show that shrinking the core of a quantum dot can enhance the ability of a surrounding polymer to extract electric charges generated in the dot by the absorption of light.
January / February 2014
www.compoundsemiconductor.net 163
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