Sen— Excitement is growing over the approach of an asteroid that will make the closest ever flyby of Earth to have been predicted well in advance later this month.
The chunk of space rock, about 50 meters (150 ft) wide, will give us such a near miss that it will skim our planet inside the geosynchronous orbits of many TV and communications satellites on 15 February.
And despite its small size, it will become visible to amateur astronomers in binoculars and small telescopes, with its rapid motion across the starry background, covering an area of sky greater than the apparent width of the Moon every minute, being quite obvious.
The asteroid, which was discovered last year, is labelled 2012 DA14 and is known as a Near-Earth Object because its orbit makes it a potential impact threat at some time in its history. Fortunately, it will not hit us this time or at any date in the predictable future.
But NASA - and the eyes and cameras of amateur and professional observatories around the world - will be watching 2012 DA14 to record this unusual visitor and to try to find out more about it.
In December, a larger 5 km-wide (3 miles) asteroid called Toutatis sped by us at a distance of 7 million km (4.3 million miles) and was imaged by Chaina's Chang'e 2 space probe and by radar by radio telescopes on Earth.
2012 DA14 will fly less than 28,500 km (18,000 miles) above the surface of the Earth at about 19.25 UT on 15 February. Its close pass will be visible in a dark sky in regions stretching from Australia, through Asia to Europe. By the time darkness falls in the US, it will be much further away again and have faded to magnitude 11 or 12.
Orbital path of 2012 DA14 as it passes the Earth. Credit: NASA
The asteroid's trajectory will carry it from the far southern part of the sky past the constellation of Crux, the Southern Cross, through Virgo and through the Plough or Big Dipper. Because it will be relatively close, the exact positions depend on where on the Earth one is observing from but a chart for your own location can be found by registering at the website Heaven's Above.
Robin Scagell, of the UK-based Society for Popular Astronomy, told Sen: "It will be quite a tricky thing to see, because you'll have to know the sky quite well so that you look at exactly the right spot. But it'll be a unique chance to see such a close asteroid - I've never witnessed anything like it in many years of skywatching."
Asteroids like 2012 DA14 and Toutatis are of great interest to the new space mining companies that have recently sprung up to harvest such objects' resources. Experts believe that 2012 DA14 is probably made of stone rather than metal or ice.
Its size may not sound very great, but the energy produced in an impact means it would leave a sizeable scar if it were to strike our planet. An asteroid of a similar size blasted the famous Barringer Meteor Crater out of the ground in Arizona around 50,000 years ago.
NASA video about the close passage of 2012 DA14. Credit: NASA
Another similar-sized but more crumbly object exploded in the air over a remote region of Tunguska, Siberia, in 1908, flattening forests for hundreds of square miles around.
But to repeat, experts have 2012 DA14's orbit well-mapped and are quite clear that this asteroid flyby is not a danger.
Don Yeomans of NASA's Near Earth Object Program at the Jet Propulsion Laboratory in California, said. "This is a record-setting close approach. Since regular sky surveys began in the 1990s, we've never seen an object this big get so close to Earth."
He added: "2012 DA14 will definitely not hit Earth. The orbit of the asteroid is known well enough to rule out an impact."