Due to the interest sparked by the upcoming flyby of 2012 DA14, I thought it would be helpful to place its flyby in an historic perspective. To do so, I put together a visualization of all the flybys of known asteroids in the 21st century:
This “Flyby Clock” illustrates the close-approach distance (both of the nominal “best fit” orbit, and of the range of orbits allowed by current measurement uncertainties) of the closest-passing known asteroids as arrayed on the face of a clock spanning the years 2000 through 2100. Also illustrated are the approximate relative sizes of each asteroid.
The illustration shows a region centered on the Earth, and spans an area three times the radius of the Moon’s orbit. The Moon’s orbit itself is drawn for scale, as is the location of the orbits of geosynchronous satellites (approximately 42,164 km). The largest asteroid which passes within the boundaries of this plot over the 2000 – 2100 timespan is 1997 XF11, and it is approximately a mile across.
One striking feature of this illustration is that before 2013 there appears to be many more flybys per year than after 2013. This is due to the fact that because these asteroids are so small and faint, our current facilities often only detect them during their close flybys. In other words, there are many, many more flybys that will occur in the 21st century but are not yet illustrated on this figure, simply because we have not discovered those asteroids yet. To the observatories!
There is a lot of information in this illustration, so the full version is linked here as a pdf (which allows zooming to see the finer details and names of each asteroid).