sentences:  (Jansky's peak radio source, one of the brightest in the sky, was designated Sagittarius A in the 1950s and, instead of being galactic "gas and dust", was later hypothesized to be emitted by electrons in a strong magnetic field.Current thinking is that these are ions in orbit around a massive Black hole at the center of the galaxy at a point now designated as Sagitarius A*.The asterisk indicates that the particles at Sagitarius A are ionized.)