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WASHINGTON, July 27 (Xinhua) -- Astronomers studying observations taken by NASA's Wide-field Infrared Survey Explorer (WISE) mission have discovered the first known "Trojan" asteroid orbiting the sun along with Earth, the U.S. National Aeronautics and Space Administration (NASA) announced Wednesday in a statement.Trojans are asteroids that share an orbit with a planet near stable points in front of or behind the planet. Because they constantly lead or follow in the same orbit as the planet, they never can collide with it. In our solar system, Trojans also share orbits with Neptune, Mars and Jupiter. Two of Saturn's moons share orbits with Trojans.Scientists had predicted Earth should have Trojans, but they have been difficult to find because they are relatively small and appear near the sun from Earth's point of view."These asteroids dwell mostly in the daylight, making them very hard to see," said Martin Connors of Athabasca University in Canada, lead author of a new paper on the discovery to be published Thursday in the journal Nature. "But we finally found one, because the object has an unusual orbit that takes it farther away from the sun than what is typical for Trojans. WISE was a game-changer, giving us a point of view difficult to have at Earth 's surface."The WISE telescope scanned the entire sky in infrared light from January 2010 to February 2011. Connors and his team began their search for an Earth Trojan using data from NEOWISE, an addition to the WISE mission that focused in part on near-Earth objects, or NEOs, such as asteroids and comets. NEOs are bodies that pass within 28 million miles (45 million kilometers) of Earth 's path around the sun. The NEOWISE project observed more than 155, 000 asteroids in the main belt between Mars and Jupiter, and more than 500 NEOs, discovering 132 that were previously unknown.The team's hunt resulted in two Trojan candidates. One called 2010 TK7 was confirmed as an Earth Trojan after follow-up observations with the Canada-France-Hawaii Telescope on Mauna Kea in Hawaii.The asteroid is roughly 1,000 feet (300 meters) in diameter. It has an unusual orbit that traces a complex motion near a stable point in the plane of Earth's orbit, although the asteroid also moves above and below the plane. The object is about 50 million miles (80 million kilometers) from Earth. The asteroid's orbit is well-defined and for at least the next 100 years, it will not come closer to Earth than 15 million miles (24 million kilometers).

LOS ANGELES, July 18 (Xinhua) -- The spacecraft Dawn of the National Aeronautics and Space Administration (NASA) has returned the first close-up image of the giant asteroid Vesta after entering its orbit for the first time last week, the Jet Propulsion Laboratory (JPL) announced on Monday.The image taken for navigation purposes shows Vesta in greater detail than ever before, said JPL in Pasadena, California.On July 15, Dawn became the first probe to enter orbit around an object in the main asteroid belt between Mars and Jupiter.When Vesta captured Dawn into its orbit, there were approximately 9,900 miles (about 16,000 kilometers) between the spacecraft and the asteroid.Vesta is 330 miles (about 530 kilometers) in diameter and the second most massive object in the asteroid belt.NASA's Dawn spacecraft obtained this image with its framing camera on July 17, 2011. It was taken from a distance of about 9,500 miles (15,000 kilometers) away from the protoplanet Vesta. Each pixel in the image corresponds to roughly 0.88 miles (1.4 kilometers). Ground- and space-based telescopes have obtained images of Vesta for about two centuries, but they have not been able to see much detail on its surface."We are beginning the study of arguably the oldest extant primordial surface in the solar system," said Dawn principal investigator Christopher Russell from the University of California, Los Angeles, which is responsible for Dawn's mission science. " This region of space has been ignored for far too long. So far, the images received to date reveal a complex surface that seems to have preserved some of the earliest events in Vesta's history, as well as logging the onslaught that Vesta has suffered in the intervening eons."Vesta is thought to be the source of a large number of meteorites that fall to Earth. Vesta and its new NASA neighbor, Dawn, are currently approximately 117 million miles (about 188 million kilometers) away from Earth. The Dawn team will begin gathering science data in August.Observations will provide unprecedented data to help scientists understand the earliest chapter of the solar system and pave the way for future human space missions, according to JPL."Dawn slipped gently into orbit with the same grace it has displayed during its years of ion thrusting through interplanetary space," said Marc Rayman, Dawn chief engineer and mission manager at NASA's JPL. "It is fantastically exciting that we will begin providing humankind its first detailed views of one of the last unexplored worlds in the inner solar system."Although orbit capture is complete, the approach phase will continue for about three weeks. During approach, the Dawn team will continue a search for possible moons around the asteroid; obtain more images for navigation; observe Vesta's physical properties; and obtain calibration data.In addition, navigators will measure the strength of Vesta's gravitational tug on the spacecraft to compute the asteroid's mass with much greater accuracy than has been previously available, according to JPL.Dawn will spend one year orbiting Vesta, then travel to a second destination, the dwarf planet Ceres, arriving in February 2015. The mission to Vesta and Ceres is managed by JPL for the agency's Science Mission Directorate in Washington.Dawn is a project of the directorate's Discovery Program, which is managed by NASA's Marshall Space Flight Center in Huntsville, Alaska.

BEIJING, Sept. 2 (Xinhuanet) -- Insomnia costs average U.S. worker 11.3 days, or 2,280 dollars, in lost productivity each year, according to a new study published in journal Sleep.The total cost to the nation is 63.2 billion dollars annually, the study said.Researchers analyzed information about sleep habits and work performance from 7,428 workers taking part in Harvard Medical School's American Insomnia Study survey in 2008-09.As a result, 23.2 percent of the participants suffered insomnia, characterized by a hard time falling or staying asleep.Moreover, insomnia rates were 19.9 percent for those with less than a high school education and 21.5 percent for college graduates."We were shocked by the enormous impact insomnia has on the average person's life," said Ronald C. Kessler, a lead author and a psychiatric epidemiologist at Harvard Medical School."It's an underappreciated problem. Americans are not missing work because of insomnia. They are still going to their jobs but accomplishing less because they're tired," Kessler noted.Employers usually ignore the consequences of insomnia because it's not considered an illness resulting in workers' absenteeism.But the high cost of lost sleep identified in this study indicates that employers need to take it more seriously.

SAN FRANCISCO, Aug. 15 (Xinhua) -- Facebook and Yahoo on Monday started to test "six degrees of separation," an iconic social experiment in the 1960s that showed everyone is on average approximately six steps away from any other person on earth.The current Facebook-Yahoo "small world" experiment, based on more than 750 million active Facebook users, is expected to determine the social path length between two strangers.Anyone with a Facebook account can participate by going to smallworld.sandbox.yahoo.com and will be assigned a "target person. " The participant will be asked to select one of his or her Facebook friends, whom will be forwarded a message and then pass the message from friend to friend so that the participant will get a message to the "target person" in as few steps as possible.The study is intended as academic social research and will be published in peer-reviews scientific journal, Duncan Watts, Yahoo' s principal research scientist who is leading the experiment, told San Jose Mercury News.In the 1960s, American social psychologist Stanley Milgram and other researchers conducted several experiments to examine the average path length for social networks of people in the United States, suggesting that human society is a small world type network by around 5.5 people steps or about six people on average.It is now currently accepted that there were potential flaws in the so-called "small world experiment" because the conclusions were based on relatively small number of research samples.

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