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New Superconductors Present New Mysteries, Possibilities
JohnsHopkinsUniversity researchers and colleagues in China have unlocked some of the secrets of newly discovered iron-based high-temperature superconductors, research that could result in the design of better superconductors for use in industry, medicine, transportation and energy generation.
Superconductors are materials that can carry electrical current without friction and as a result, don't waste electrical energy generating heat. (Imagine your laptop computer or PC not getting warm when it is turned on.) This means that an electrical current can flow in a loop of superconducting wire forever without a power source. Today, superconductors are used in hospital MRI machines, as filters in cell phone base stations and in high-speed magnetic levitating trains. Unfortunately, most of today's superconducting materials can only function and operate at extremely low temperatures, which means that they must be paired with expensive supercooling equipment. This presents researchers with a grand challenge: to find superconducting material that can operate at more "normal" temperatures.
"If superconductors could exist at room temperatures, the world energy crisis would be solved," Chen said.
Chen explains that though all metals contain mobile electrons which conduct electricity, a metal becomes a superconductor only when two electrons with opposite "spins" are paired. The superconductor energy "gap," which is the amount of energy that would be needed to break the bond between two electrons forming such a pair to release them from one another, determines the robustness or strength of the superconducting state. This energy gap is highest at low temperatures, but vanishes at the temperatures at which superconductivity ceases to exist.
"This gap -- its structure and temperature dependence -- reveal the 'soul' of the superconductor, and this is what was measured in our experiment," Chien said.
The team measured this gap and its temperature variation, revealing that the pairing mechanism in iron-based superconductors is different from the one in more traditional, copper-based, high-temperature superconductors. To the researchers' surprise, their results were incompatible with some of the newly proposed theories in this mushrooming field.
Hunt For Superearth Planets Underway
NASA's EPOXI mission, which uses the Deep Impact spacecraft, has begun its search for "super Earth" planets.
The EPOXI team has focused its attention on the star GJ436. This red dwarf star which is 32 light-years from Earth has a Neptune-sized planet that transits in front of the star. Spitzer observations have shown that this Neptune-sized planet has an oval shaped orbit (eccentric).
The orbital period of the “super Earth” is not precisely known, but the EPOXI team estimates it to be in the range from 20 to 30 days. EPOXI has been observing the system from May 5 – May 28. Deming and his team are in the process of analyzing the results of these data.
In addition to targeting the red dwarf star for study, EPOXI imaged the Earth over three 24-hour periods. EPOXI measured the Earth’s rotational light curve at visible wavelengths from the ultraviolet to the near-infrared. These observations will help to calibrate future observations of Earth-like exoplanets. EPOXI obtained a particularly interesting view of the Earth on May 29, when the Moon passed in front of the Earth as viewed from the spacecraft. This "transit" of the Moon is an event that may also be observed to occur for Earth-like exoplanets, and it may help us to deduce the nature of their surface features.
EPOXI is a combination of two separate science investigations. The investigations consist of the Extrasolar Planet Observations and Characterization (EPOCh), and the flyby of comet Hartley 2, called the Deep Impact eXtended Investigation (DIXI) which is lead by Dr. Michael A’hearn at the University of Maryland. Deming is the Principal Investigator on the EPOCh investigations. EPOCh observations began in January 2008. Professor A'Hearn is the Principal Investigator for the combined EPOXI mission.
