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	2004 MN4

These odds are changing on a day-to-day basis as new data is received. In all likelihood, the possibility of impact will eventually be eliminated as the asteroid continues to be tracked by astronomers around the world. On December 23, 2004, when this page was posted, the object was about 14 million km away from the Earth.

The odds of a collision have been updated (24^th Dec) to 1 in 60, a five-fold improvement. This corresponds to a rating of 4 on the ten-point Torino Scale,
and again (25th Dec) to 1 in 43
and again (26th Dec) to 1 in 37

UPDATE:

(4th Feb 2005)

	2004 MN4

An Earth collision in 2029 is 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 may influence a number of future Earth close approaches. The current risk analysis indicates that no subsequent Earth encounters in the 21st century are of concern.
Based on unpublished albedo constraints, the diameter of the object is about 320 meters. At the time of the closest approach, the asteroid will be a naked eye object (3.3 mag.) travelling rapidly at 42 degrees per hour, through the constellation of Cancer.
On average, one would expect a similarly close Earth approach by an asteroid of this size only every 1300 years or so.

The passage of the asteroid by the Earth in 2029 will alter its subsequent trajectory and causes its position uncertainty region to expand rapidly as it moves away from Earth. As a result, the asteroid's motion is much less predictable after the 2029 close Earth approach. 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.

UPDATE:

(28th Dec 2004)

"Sleep easy - this one is safe, for now"

to reach a level 2 (out of 10) on the Torino Scale. According to the Torino Scale, a rating of 2 indicates "a discovery, which may become routine with expanded searches, of an object making a somewhat close but not highly unusual pass near the Earth. . New telescopic observations very likely will lead to re-assignment to Level 0 [no hazard]." This asteroid should be easily observable throughout the coming months.
(updated to 4 , 26th Dec )
(updated to 0 , 28th Dec )

Most of this object's orbit lies within the Earth's orbit, and it approaches the sun almost as close as the orbit of Venus. 2004 MN4's orbital period about the sun is 323 days, placing it within the Aten class of NEAs, which have an orbital period less than one year. It has a low inclination with respect to the Earth's orbit and the asteroid crosses near the Earth's orbit twice on each of its passages about the sun.

The brightness of 2004 MN4 originally suggested that its diameter is roughly 380 meters and the current, but very uncertain, best estimate of the flyby distance in 2029 is about 390,000 km (about the distance of the moon).
If the orbit did coincide with the orbit of the Earth, then the speed and size would translate to an impact event of about 1,400 megatons of energy.

On average, an asteroid of this size would be expected to pass within 2 lunar distances of Earth every 5 years or so.

Many astronomers assume that the albedo - like comet albedos - is around four percent and have used that number to calculate diameters. If it's very dark, the mass could be quite a bit larger.
However, it must be said that results from the Spitzer Space Telescope survey of 30 Kuiper Belt Objects, that they reflects 18 % of their incident light and therefore 2004 MN4 maybe considerably smaller and more reflective than expected. (of course 2004 MN4 is not a KBO)

	Click to expand

Period : 1.2764 days
 for lightcurve file (PDF)
      

 Object (and name)    Date of encounter (TT)       Distance                
             JD          Calendar                  (AU)
2004 MN4     462240.44   2029 Apr. 13.94           0.0005379             
2004 MN4     462241.19   2029 Apr. 14.69           0.001375      

	N49B

On 18 December, the object was rediscovered from Australia by Gordon Garradd of the Siding Spring Survey, another NASA-funded NEA survey. Follow-up observations over the next several days allowed the connection to the June discovery to be made, at which point the possibility of impact in 2029 was realized by the automatic SENTRY system of NASA's Near-Earth Object Program Office. NEODyS, a similar automatic system at the University of Pisa and the University of Valladolid, Spain also detected the impact possibility and provided similar predictions.