In April 1993, the ASCA satellite observed X-rays from a supernova in the
galaxy M81 (which is also called NGC 3031). Scientists gave the source
the name "SN 1993J", which means that it was the 10th supernova
observed to occur in the year 1993. The source is clearly seen showing up a
few arcminutes away from the center, or core, of M81, where the X-rays from
the relatively faint 'active nucleus' (or a micro-quasar) can be seen. The
observations were made only 10 days after the supernova explosion occurred.
Also seen in the movie is the image of an X-ray binary near the supernova.
They are clearly separated, even though they are a close 1 arcminute apart
on the sky (the real distance between the two is, well, astronomical!).
This shows the excellent spatial resolution of the ASCA instruments.