Big asteroid to zoom by Earth on Australia Day

A large asteroid about half a kilometre wide will zoom safely by Earth this month, and mark the planet's closest encounter with a space rock of its size until 2027.

The asteroid 2004 BL86 will fly by Earth on January 26, passing at a range of about 1.2 million kilometres, about three times the distance between the Earth and the moon.

It will be the asteroid's closest approach to Earth for the next 200 years, according to NASA scientists.

Asteroid 2004 BL86 is nearly 549 metres in diameter, but there is no risk of it hitting the Earth when it zips by.

The next asteroid of similar size to come near Earth will be the asteroid 1999 AN10, which will make its closest approach in 2027, according to the NASA statement.

"While 2004 BL86 poses no threat to Earth for the foreseeable future, it's a relatively close approach by a relatively large asteroid, so it provides us a unique opportunity to observe and learn more," Don Yeomans, of NASA's Near Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, California, said in a statement.

Astronomers will track asteroid 2004 BL86 with radar during its fly-by by using the massive dish-shaped antennas at NASA's Deep Space Network in Goldstone, California, and the Arecibo Observatory in Puerto Rico.


The 600-metre asteroid 2004 BL86 will make its closest approach to Earth for the next 200 years on January 26, 2015. This NASA graphic shows the position of the asteroid in relation to Earth. Photo: Supplied
The 600-metre asteroid 2004 BL86 will make its closest approach to Earth for the next 200 years on January 26, 2015. This NASA graphic shows the position of the asteroid in relation to Earth. Photo: Supplied

These radio dishes will beam microwave signals at the asteroid, which will then bounce off the target, and return to Earth.

The resulting radar 'echo' looks like a sonogram and can reveal details about the asteroid's three-dimensional shape, its rotation and even its internal density.

Although this method has detected echoes from about 200 near-Earth asteroidsbefore, no two are the same.

"At present, we know almost nothing about the asteroid, so there are bound to be surprises," said JPL astronomer Lance Benner, who is the principal investigator for the Goldstone observations of the asteroid.

Astronomers first detected the asteroid on January 30 in 2004, with the 1-meter LINEAR telescope in New Mexico.

"Asteroids are something special. Not only did asteroids provide Earth with the building blocks of life and much of its water, but in the future, they will become valuable resources for mineral ores and other vital natural resources," Mr Yeomans said.

"They will also become the fueling stops for humanity as we continue to explore our solar system. There is something about asteroids that makes me want to look up."

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