In Focus

NASA's WISE finds Earth's first 'Trojan' asteroid

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.

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 in the July 28 issue of 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 kilometres) 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 metres) 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 kilometres).

"It's as though Earth is playing follow the leader," said Amy Mainzer, the principal investigator of NEOWISE at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Earth always is chasing this asteroid around."

A handful of other asteroids also have orbits similar to Earth. Such objects could make excellent candidates for future robotic or human exploration.

Asteroid 2010 TK7 is not a good target because it travels too far above and below the plane of Earth's orbit, which would require large amounts of fuel to reach it.

"This observation illustrates why NASA's NEO Observation programme funded the mission enhancement to process data collected by WISE," said Lindley Johnson, NEOWISE program executive at NASA Headquarters in Washington. "We believed there was great potential to find objects in near-Earth space that had not been seen before."

NEOWISE data on orbits from the hundreds of thousands of asteroids and comets it observed are available through the NASA-funded International Astronomical Union's Minor Planet Center at the Smithsonian Astrophysical Observatory in Cambridge, Mass.

ScienceDaily

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History

1. Who were the original inhabitants of Rome that were driven away in 275 B.C?

2. During which wars were the powerful rivals of Rome defeated by the Romans?

3. Who introduced the Feudal system to Britain?

4. The Mongols never had permanent homes. They lived in large circular tent-like homes .What were they called?

5. What is the ' Domes Day Book' and by what other names was it called?

6. How were hieroglypics understood?

7. World War I was the first mechanised war in the history of mankind.True/false?

8. Horses were introduced to American Indians during the 5th century when Europeans who came to America brought horses with them .True/False?

9. Who built the hanging Gardens of Babylon and why?

10. In which year did Mao-Tse Tung proclaim the establisment of the Chinese People's Republic?

11. In which year did Chiang Kei Sheck set up a Nationalist Republic in Formosa which was later known as Taiwan?

12.When did the American's enter WW2 which involved nearly 60 nations?

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[Answers]

History

1. The Etruscans.

2. During the Punic Wars (261-146B.C)

3. The Normans .Under this systyem the king owned all the land and others could hold land in exchange of providing services to the king.

4. The homes of the Mongols were known as Yurts. They were made of felt that were fastened over light wooden frames. The whole structure could be dismantled and carried by horses. The Mongols carried their homes with them during migration and invasion.

5. The ' Domes Day Book' was also known as the 'Winchester Roll' and The King's Book'.In AD 1085 Norwegian king, William I ordered a survey of land in England.

The findings were written in two volumes in Latin. It was completed in 1806.

The book listed every single town,village,farm owners,properties and assests. The value of each property was also entered so that taxes could be imposed.

6. Hieroglypics were a system of writing used by the ancient Egyptians around 3000 B.C.They had a pictorial script. It was the discovery of the 'Rosetla Stone'that helped to understand the complicated pictures.

7. True.Aircrafts were used for the first time to observe the enemy and locate targets for long-range artillery fighting.Planes were used to shoot down the spotters introducing aerial warfare .Airships were used as bombers.The most terrifying new weapon used by both sides was the poison gas. Tanks also made their appearance in WW2

8.True.

9. It was built under the insructions of King Nebuchadnessar. He married a Mede princess who was homesick for the greenery in her native land, so the king had the garden built as a gesture of love and afffection.

10. On October 1,1949.

11. In 1950.

12. In 1941.