Figure 8. Main picture: A MERLIN+VLA radio image of the central region of the nearby starburst galaxy M82 made at a wavelength of 20cm and with the LT in MERLIN. The bright spots are remnants of supernova explosions which took place within the last few hundred years. The diffuse emission is th esum of older remnants which have long since expanded and lost their recognisable shapes.

Inset, bottom left: Images of one of the supernova remnants in M82 made with the EVN in 1986 and 1997. The later image is of high quality and clearly shows the expected shell-like shape; a comparison of these images reveals that the shell is expanding at a speed of ~10,000 km/sec, implying that the remnant is about 30 years old.

Inset, bottom right: A MERLIN image of a much larger, more diffuse remnant than the one shown at left, made at a wavelength of 6cm. It also shows the characteristic centre-darkened structure. The LT cannot currently contribute to MERLIN at 6cm wavelength and hence the signal-to-noise ratio is limited. Nevertheless, MERLIN has revealed that many of the compact sources in M82 have shell-like structures.