We compare recent observations of the supernova remnant G11.2 - 0.3 taken with the VLA during 2001 - 02 with images from VLA archives ( 1984 - 85 ) to detect and measure the amount of expansion that has occurred during 17 years .
The bright , circular outer shell shows a mean expansion of ( 0.71 \pm 0.15 ) % and ( 0.50 \pm 0.17 ) % , from 20- and 6-cm data , respectively , which corresponds to a rate of 0 \farcs 057 \pm 0 \farcs 012 /yr at 20 cm and 0 \farcs 040 \pm 0 \farcs 013 /yr at 6 cm .
From this result , we estimate the age of the remnant to be roughly between 960 and 3400 years old , according to theoretical models of supernova evolution .
This is highly inconsistent with the 24000 yr characteristic age of PSR J1811 - 1925 , located at the remnant ’ s center , but , rather , is consistent with the time since the historical supernova observed in 386 AD .
We also predict that G11.2 - 0.3 is currently in a pre-Sedov evolutionary state , and set constraints on the distance to the remnant based on Chandra X-ray spectral results .