Close encounters with Asteriod 2005 YU55

Goldstone radar image of asteroid 2005 YU55 taken November 7, 2011

If I’m not mistaken, sometime this morning, an asteroid named 2005 YU55 made its closest recorded approach to the Earth.

Discovered on December 28, 2005 by Robert S. McMillan of the Spacewatch Program at the Steward Observatory in Kitt Peak, near Tucson, Arizona, asteroid 2005 YU55 was expected to have passed by the earth (8 November 2011 at 23:28 UT) from a lunar distance of 0.85 (324,600 kilometers or 201,700 miles). This is said to be the closest known approach by an asteroid with an absolute magnitude this bright since asteroid 2010 XC15 passed by within 0.5 lunar distances way back in 1976.

Early last year 2005 YU55 was rated 1 on the Torino Scale signifying that its passing near the Earth would pose no high level of threat. Greatly accurate radar targeting by the Arecibo radio telescope on the same year erased any likelihood of an Earth impact in the next 100 years. It has since then been removed from the Sentry Risk Table and has a current rating of 0 on the Torino Scale.

Trajectory of asteroid 2005 YU55 compared to the orbits of the Earth and the Moon on 8–9 November 2011

Measured approximately 400 meters across, asteroid 2005 YU55 is relatively bigger than an aircraft carrier. According to Professor Jay Melosh who specializes in Earth and atmospheric sciences at Purdue University, if it were to hit land, he estimates the asteroid shall form a crater four miles wide or 6.3 kilometers across and 1,700 feet (518m meters) deep, and would generate a 7.0 magnitude earthquake and 70-foot-high tsunami waves.

Famous flybys of Near-Earth objects

The next time a known asteroid this size shall come this near to the Earth (that we expect in advance) will be in 2028 when asteroid (153814) 2001 WN5 passes 0.00166 AU (248,000 km; 154,000 mi) or within 0.6 lunar distances from the Earth.

Roughly spherical and spinning slowly, 2005 YU55 was examined to be darker than charcoal, according to NASA’s radar observations. Categorized as a C-type asteroid, it is believed to be rich in carbon-based molecules, life’s building blocks here on our planet. Billions of years ago, when the solar system was still in its infancy, asteroids like 2005 YU55 likely fell on Earth almost on a regular basis carrying organic carbon-based materials forming primeval soups of life.

It is said that many asteroids often pass this close, but most are relatively minute. Moreover, these cosmic objects while numbering in the thousands plunge into the atmosphere every day, but consequently burn up posing no danger to man.

In its present condition, I wouldn’t have probably seen it anyway even if it was evening here in the Philippines. At its brightest, it is said to appear like a magnitude 11 star, which is about a hundred times dimmer than the limit of human vision if a person was looking at the night sky from a dark place and in clear weather. Amateur astronomers may be able to spot it slowly moving against the stellar background that is if their telescopes have a very wide aperture.

May this near-Earth object’s passage serve as a strong wake up call to the countries of the world that we need to work together and at least PLAN what to do if some asteroid in the future seems to be in a collision course with our planetary home.

For now, 2005 YU55 disappears into the void, following an elliptical orbit that will bring it near to the sun as Venus and as far away as Mars.