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Earth to be buzzed by asteroid

Radar image of asteroid 2005 YU55

This radar image of asteroid 2005 YU55 was generated from data taken in April of 2010 by the Arecibo Radar Telescope in Puerto Rico. The 400-metre-wide space rock will zip past Earth on November 9 (Sydney time).

EARTH IS GOING TO BUZZED by a 400-metre-wide asteroid next week, in a near miss that will bring the space rock to within a distance closer than the Moon.

NASA scientists will track the object, known as 2005 YU55, with antennae of the agency’s Deep Space Network at Goldstone, California, as it flies past Earth on November 9 (Sydney time).

Scientists are treating the flyby as a ‘target of opportunity’, giving instruments on ‘spacecraft Earth’ the chance to scan it during the close pass.

Tracking of the aircraft carrier-sized asteroid will begin on November 4 using Goldstone’s huge 70-metre-wide Deep Space Network antenna, and last for about two hours. Goldstone will continue to track the asteroid for at least four hours each day through to November 10.

Radar observations from the Arecibo Planetary Radar Facility in Puerto Rico will begin on November 8, with the asteroid due to make its closest approach to Earth at 10:38am on November 9, Sydney time.

No danger

The trajectory of asteroid 2005 YU55 is well understood. At the point of closest approach, it will be no closer than 324,600 kilometres or 0.85 the distance from the moon to Earth.

The gravitational influence of the asteroid will have no detectable effect on anything here on Earth, including our planet’s tides or tectonic plates.

Although 2005 YU55 is in an orbit that regularly brings it to the vicinity of Earth (and Venus and Mars), the 2011 encounter with Earth is the closest this space rock has come for at least the last 200 years.

Goldstone and Arecibo dishes

NASA's 70-metre-wide dish at Goldstone in California (left) and the US National Science Foundation's 305-metre-wide dish at Arecibo Observatory in Puerto Rico, will track the asteroid as it passes Earth.

During tracking, scientists will use the Goldstone and Arecibo antennas to bounce radio waves off the space rock. Radar echoes returned will be collected and analysed.

NASA scientists hope to obtain images of the asteroid from Goldstone as fine as about 2 metres per pixel. This should reveal a wealth of detail about the asteroid’s surface features, shape, dimensions and other physical properties (see “Radar Love”).

Arecibo radar observations of asteroid 2005 YU55 made in 2010 show it to be approximately spherical in shape. It is slowly spinning, with a rotation period of about 18 hours. The asteroid’s surface is darker than charcoal at optical wavelengths.


The last time a space rock as big came as close to Earth was in 1976, although astronomers did not know about the flyby at the time. The next known approach of an asteroid this large will be in 2028.

NASA detects, tracks and characterises asteroids and comets passing close to Earth using both ground- and space-based telescopes. The Near-Earth Object Observations Program, commonly called “Spaceguard,” discovers these objects, characterises a subset of them, and plots their orbits to determine if any could be potentially hazardous to our planet.

More information about asteroids and near-Earth objects.

More information about asteroid radar research.

More information about the Deep Space Network.

Adapted from information issued by NASA / JPL. Images courtesy NASA / Cornell / Arecibo, and H. Schweiker / WIYN and NOAO / AURA / NSF.

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