The asteroid 2005 YU55 came within the Moon’s orbit on November 8, 2011. It is 1,300 feet wide and came to within 201,700 miles of the Earth. This is 0.85 lunar distances, 319,000 kilometers, or 0.00217 AU. AU is an astronomical Unit, which is the distance from the Earth to the Sun. It is moving away from Earth now at the speed of 29,000 miles per hour. It had not happened for 35 years (1976). An asteroid is not expected to come close to Earth again until the year 2028.
The asteroid was discovered on December 28, 2005 by Robert McMillan at the Lunar And Planetary Laboratory of the University of Arizona during the Spacewatch survey. Many instruments took pictures of the giant rock, including the radio telescope at Arecibo Observatory in Puerto Rico and NASA’s Deep Space Network Facility in Goldstone, California. They are trying to get data about its size, physical features, and orbit. The asteroid orbits the Earth every fifteen months.
The Clay Center Observatory in Massachusetts and the online telescope service Slooh provided live online broadcasts of its close approach. It came close to the star Altair. The asteroid cannot be seen without the aid of a telescope. Its current location can be found at JPL’s Solar System Dynamics website. A radar movie of the asteroid was taken by NASA’s Goldstone Solar System Radar on November 7, 2011. It is a giant rock that is steadily revolving on its axis. The Jet Propulsion Laboratory distributed some information about the asteroid.
Comet Elenin (also called C/2010 X1), discovered in December 2010 by Russian astronomer Elenin, was also predicted to come close to the Earth on November 7, 2011, just one day before asteroid 2005 YU55. It was feared that the two bodies might collide with each other and cause one or both to hit the Earth. But the comet’s dust was detected on about October 21, 2011 by the team of observers at the Remanzacco Observatory in Italy. They study small bodies in the solar system using telescopes.
Similar to the asteroid, the first known Earth Trojan (2010 TK7) discovered might come very close to the Earth in about ten years. A Trojan is an asteroid that shares the Earth’s orbit, meaning it intersects it at times. It was discovered by NASA’s WISE Mission using NEOWISE. Lagrange points are used to track the asteroid. NASA’s wide-field infrared Survey Explorer found that there are only 20,500 asteroids larger than 100 meters compared to the 36,000 predicted before.
The asteroid Icarus (asteroid 1566) will also come close to the Earth on June 16, 2015, although the predicted distance is 5 million miles from the Earth. Icarus was discovered in 1949 by Walter Baade. It came within 16 lunar distances or 4 million miles on June 14, 1968. It is classified as a Mercury/Venus/Mars crossover asteroid. Icarus orbits the Sun in about 1.12 years.