Back in November, the asteroid 2005 YU55 passed inside of 202,000 miles of the Earth -- or just inside of the Moon's orbit. It is one of the many space rocks and objects that travel through our Solar System and pass relatively near the Earth. Although projections are not precise as yet (gravity being what it is, there is an uncertainty region built into trajectory calculations), it is believed that 2005 YU55 just might impact the Earth in less than a century. Another large planetoid speeding through space on a near-Earth trajectory, 2011 AG5, recently prompted discussion in Vienna, Austria, at the 49th session of the Scientific and Technical Subcommittee of the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS). Why? Because there is the very real fear that 2011 AG5 could possibly be on a collision course with Earth by 2040.
The meeting of COPUOS and the near-Earth orbital path chartings of the space rock -- it is about 140 meters (460 feet) wide -- have triggered calls for scientists to meet to discuss ways of deflecting the object, according to Space.com.
The object's mass and composition are as yet unknown. Still, given its size, it could still do considerable damage, depending upon where on Earth it were to impact.
Dr. Jay Melosh at Purdue University estimated that the aforementioned 2005 YU55, which was 400 meters (1312 feet or one-quarter mile) wide, could, if it were to strike land, produce an impact crater nearly 4 miles wide and 518 meters (1,699 feet) deep. It would also generate a 7 magnitude seismic event. If it were to land in the ocean, it could produce a tsunami 70 feet high within 60 miles of the crash zone.
2011 AG5 is just over one-third the size of 2005 YU55, which was described as being the size of an aircraft carrier. However, depending upon its mass and composition, 2011 AG5, which could be compared to being nearly the size of a destroyer (in keeping with the naval ship size comparisons) could be every bit as devastating upon impact.
Still, little is known about the massive space rock and that paucity of information will continue due to its position in the sky, which makes it difficult to observe. But in September 2013 it will be 91 million miles from Earth and more can be learned from its passage. Another passage in 2015 will allow for an even more accurate trajectory projection.
At present, 2011 AG5 is the most likely near-Earth object to realize an actual impact with the Earth. According to Donald Yeomans, head of the Near-Earth Object Observations Program at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., the space rock has a 1 in 625 chance of colliding with the Earth on Feb. 4, 2040.
2005 YU55 is currently projected to make a pass by the Earth in 2041 that will bring it within 9.5 million miles of Earth.
Talk of deflection might be premature because of the limited time in which the object has been observed (it was discovered in January 2011). But if the trajectory path is deemed to be accurate and threatening, there would be time to mount a deflection exercise by the time of its next close passage, which would be in 2023. It will at that time pass within 0.02 astronomical units of Earth, or just under 1.9 million miles.
"Again, it is important to note that with additional observations next year the odds will change and we expect them to change in Earth's favor," said Yeomans, according to PhysOrg.com.
It is estimated, according to a NASA study conducted using the Wide-Field Infrared Survey Explorer, that there are some 19,500 mid-size near-Earth objects (between 330 and 3,300 feet wide and large enough to destroy a city) traveling through our Solar neighborhood. 2011 AG5 was only discovered a year ago. The study, which concluded in September, also estimated that 10 percent of all near-Earth Objects have yet to be found, including about 70 asteroids in the "killer" class that ranges between 1 kilometer and larger.
(photo credit: MagicKnight94, Wikimedia Commons)