Asteroids sweep by Earth all the time but one is particularly attracting attention, given its size and how close it will be flying by the planet.

Called 2004 BL86, the asteroid is estimated to be about a third of a mile in diameter based on its reflected brightness. Coming in as close as 745,000 miles from Earth, equivalent to around three times the distance of the moon to the planet, 2004 BL86 will be making the closest flyby for an asteroid until 1999 AN10 whizzes past in 2027.

"Monday, January 26 will be the closest asteroid 2004 BL86 will get to Earth for at least the next 200 years. And while it 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," said Don Yeomans, former Near Earth Object Program Office manager from the Jet Propulsion Laboratory in California. Yeomans retired last Jan. 9.

One of the way NASA aims to learn more about the asteroid is to use microwaves to observe it. Puerto Rico's Arecibo Observatory and NASA's Deep Space Network antenna will be attempting to gather data and images generated by radar during the days 2004 BL86 is close to Earth.

Lance Benner, principal investigator for the Deep Space Network antenna, said that images received by radar will be the first detailed ones of the asteroid. Next to nothing is known about 2004 BL86 at this point so scientists are preparing for any and all surprises.

Amateur astronomers should be able to spot the asteroid using strong binoculars and small telescopes starting Jan. 26 in the evening, running into the morning of the next day. Peak brightness is expected at around magnitude 8.8 so it won't be visible to the naked eye.

Europe, North America, South America and Africa will have the best seats in the house for observing the flyby. Those in east Asia and Australia will have to look to the skies a few hours earlier, at a time when 2004 BL86 will not be at its brightest.

Moving around four degrees for every hour, the asteroid will be passing in front of the Leo, Cancer and Hydra constellations. That's fast, or at least faster than the moon, which moves at around half a degree for every hour.

Asteroid 2004 BL86 was discovered by the Lincoln Near-Earth Asteroid Research survey in 2004 in White Sands in New Mexico.

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