|P/2010 A2: Scales|
Caption: Changes in P/2010 A2 at four epochs, shown both as positive and negative versions, with direction and scale bars. Note that 24,000 km (the length of the scale bar in each panel) is about twice the diameter of the Earth. [Click on the figure to see larger versions of each panel].
The shrinkage of the tail to a thin line at later dates is due, in part, to the collapse of the dust back towards the orbit plane of A2. Exactly half way around the orbit (after 21 months from the dust ejection) the tail should all lie in the orbit plane. If the earth were in the orbit plane, too, the tail would appear as an infinitely thin line across the sky. This will happen in November of 2010, but A2 will be invisible then as a result of being at too small an angle from the Sun to be observed.