The newly discovered object, officially designated 2011 CQ1, is shown in this image from Tzec Maun Observatory in New Mexico. G. Sostero & E. Guido/Remanzacco Observatory
Trajectory of Asteroid 2011 CQ1 - February 4, 2011, Source: NASA JPL
From Don Yeomans and Paul Chodas at JPL...
Asteroid 2011 CQ1 was discovered by the Catalina Sky Survey on February 4 and made a record close Earth approach 14 hours later on February 4 at 19:39 UT (14:39 EST). It passed to within 0.85 Earth radii (5480 km) of the Earth's surface over a region in the mid-Pacific. This object, only about one meter in diameter, is the closest non-impacting object in our asteroid catalog to date. Prior to the Earth close approach, this object was in a so-called Apollo-class orbit that was mostly outside the Earth's orbit. Following the close approach, the Earth's gravitational attraction modified the object's orbit to an Aten-class orbit where the asteroid spends almost all of its time inside the Earth's orbit.
As is evident from the diagram, the close Earth approach changed the asteroid's flight path by about 60 degrees. Because of their small size, object's of this size are difficult to discover but there is likely to be nearly a billion objects of this size and larger in near-Earth space and one would expect one to strike Earth's atmosphere every few weeks on average. Upon striking the atmosphere, small objects of this size create visually impressive fireball events but only rarely do even a few small fragments reach the ground.
Link: NASA JPL NEO page post ("Very Small Asteroid Makes Close Earth Approach on February 4, 2011")
From the Scientific American post (also space.com article) on Asteroid 2011 CQ1...
The solar system is littered with natural debris—asteroids, comets and pieces of the same that occasionally wind up in the steamrolling path of one of the planets. When a piece of debris encounters the friction of Earth's atmosphere, it flares up as a meteor, or shooting star, and pieces of the object may survive the heat of reentry to reach the surface as meteorites.
Many more objects whiz past Earth without striking the atmosphere, perhaps returning for another pass some years later. Many of those go undetected, especially the small asteroids that are harder to spot with the relatively modest telescopes that keep watch for near-Earth objects.
But sky monitors did spot one small asteroid, called 2011 CQ1, less than a day before it buzzed Earth at the smallest distance ever recorded. On February 4, the meter-size rock flew over the Pacific at an altitude of about 5,500 kilometers—about one-seventieth the distance between Earth and the moon and well below the orbit of some high-flying satellites.
But even though 2011 CQ1 skirted immolation in Earth's atmosphere, it did not escape from the encounter unmolested. Earth's gravity gave the asteroid a good tweak, redirecting its trajectory by about 60 degrees in much the same way that interplanetary spacecraft use the gravity of the planets for course corrections or speed adjustments. "Prior to the Earth close approach, this object was in a so-called Apollo-class orbit that was mostly outside the Earth's orbit," asteroid trackers Don Yeomans and Paul Chodas wrote on the NASA Near-Earth Object Program Web site. "Following the close approach, the Earth's gravitational attraction modified the object's orbit to an Aten-class orbit where the asteroid spends almost all of its time inside the Earth's orbit."
Just what is in store for the tiny asteroid is unclear—faint as 2011 CQ1 is, it was visible only briefly, when it was very close to Earth, and its newly adjusted orbit is not well understood.
Link: Scientific American post ("Record-setting "near miss" of Earth dramatically shifted tiny asteroid's orbit")
