Sir, - Your correspondent, J.Connolly, reports in a somewhat exalted style about a celestial object, Galaxy Markarian 421, that scientists at UCD would have discovered to be of violent nature, as demonstrated by its extremely high energy emission at gamma rays (October 29th). Serious science journalism, however, should put such results in proper perspective.
Whereas this galaxy has produced a truly dramatic flare at such extremely high energies, it was by no means discovered as an outstanding object at this occasion, as The Irish Times report suggests. It has been well known since the 1970s, and observations at X rays and gamma rays have singled it out as abnormally active for the last 12 years or so.
Indeed, the still operational, high energy satellite observatory GRO has consistently drawn the attention to this remarkable object, preparing the ground for the Whipple Observatory measurements now in the news. These remarks obviously do not diminish in any way the value of the results obtained by UCD. - Yours, etc,
Director,
Dunsink Observatory, Castleknock, Dublin 15.