Mountain-size asteroid to fly by Earth on Jan 26-27

A relatively large asteroid, designated 2004 BL86, is going to fly by Earth at a very safe distance of 745,000 miles (1.2 million km).

This interplanetary visitor is roughly a third of a mile across and is the largest known space rock predicted to come this close to us until 2027 as by comparison, most near-Earth asteroids have diameters no larger than 50 to 100 feet.

Because it's relatively large, 2004 BL86 will brighten rapidly as it approaches Earth and astronomers predict it will become about 9th magnitude for several hours as it passes closest to us.

This is still much too faint to be seen by eye, and it is beyond the reach of most binoculars, but this object should be bright enough to follow with a 3- or 4-inch-diameter telescope as it moves among the stars.

Alan MacRobert, a senior editor at Sky and Telescope magazine, said that to track down the asteroid, people'll need a detailed star chart that shows the exact path of 2004 BL86 and their charts were specially prepared for this event.

Observers in the Americas, Europe, and Africa have the best seats for seeing this interloper during its brightest time: from 8 p.m. Eastern Standard Time on Monday evening, January 26th, until about 1 a.m. EST on the 27th and during this time 2004 BL86 will be heading northward through the dim constellation Cancer. It skims the eastern edge of a star cluster called the Beehive (or Messier 44) from about midnight to 12:30 a.m. EST.

Kelly Beatty, also a Sky and Telescope senior editor, said that one good technique for fast-movers like 2004 BL86 is to identify and lock onto a star along its path and then just watch at the time that the asteroid is predicted to pass by that particular star.