The name Mn4 is taken from an asteroid that will come very close to earth in 2029.
No panic, it will miss, but may be visible with the naked eye and is being tracked by Nasa.
  Mn4 Nasa News

RadaRefine the Future Motion of Asteroid 2004 MN4
Paul Chodas, Steve Chesley, Jon Giorgini and Don Yeomans
NASA's Near Earth Object Program Office
February 3, 2005

Radar observations taken at the Arecibo Observatory in Puerto Rico on January 27, 29, and 30 have significantly improved our estimate for the orbit of asteroid 2004 MN4 and changed the circumstances of the Earth close approach in 2029. On April 13, 2029, the predicted trajectory now passes within 5.7 Earth radii (36,350 km or 22,600 miles) of the Earth's center - just below the altitude of geosynchronous Earth satellites. However, an Earth collision in 2029 is still ruled out. The asteroid's motion subsequent to the 2029 Earth close approach is very sensitive to the circumstances of the close approach itself and a number of future Earth close approaches will be monitored as additional observations are received. However, our current risk analysis for 2004 MN4 indicates that no subCloseup Viewsequent Earth encounters in the 21st century are of concern. 

The passage of the asteroid by the Earth in 2029 alters its subsequent trajectory and causes its position uncertainty region to expand rapidly as it moves away from Earth (i.e., the line of white dots increases in extent). As a result, the asteroid's motion is much less predictable after the 2029 close Earth approach. Even so, the asteroid's uncertainty region is not large enough to extend to the moon as it passes by, and so a lunar impact is not possible.

Former Apollo astronaut Rusty Schweickart explains the potential impact risk posed by 2004 MN4 during his talk at the 2005 International Space Development Conference in Washington. (click here)