Mysterious dying radio galaxy discovered by Pune astronomersNov 9(AZINS) Ghost of a rare giant radio galaxy was discovered by Indian astronomers from the National Centre for Radio Astrophysics (NCRA, TIFR) in Pune have discovered, using the Giant Metrewave Radio Telescope (GMRT).

The galaxy, J021659-044920, is 9 billion light years away from Earth making it one of the oldest galaxies ever discovered. What makes this one special is that it is a dying galaxy.

Radio galaxies discharge strong massive radio waves that are very different from the optical signals of similar galaxies. The gigantic radio galaxies are rare and this one emits radio signals that are equivalent to an extent of four million light years.

The strange thing about J021659-044920 is that it is only a few hundred thousand light years in optical size (pretty small for a galaxy in cosmic terms) and yet somehow generates multi-million light years worth of radio waves.

Experts theorise the presence of a giant black hole at the centre that is shooting out jets of hot plasma in opposite directions which produce huge 'lobes' of radio emissions.

Under some special circumstances, the central black hole may stop producing the radio jet, and then the bright radio lobes fade away, within a few million years, due to lack of replenishment.  This dying phase is where the radio jet appears to have switched off and the radio lobes have started fading.

Because J021659-044920 is so far away, its radio lobes probably faded out long ago, but their light is only now reaching Earth.

Prathamesh Tamhane, a student at the Indian Institute of Science Education and Research, and his colleagues published their discovery in the Monthly Notices of the Royal Astronomical Society.