Indian astronomers discover rare giant radio galaxy

When Prathamesh Tamhane, a student at the Indian Institute of Science Education and Research, and his colleagues looked at J021659-044920 in the radio spectrum, they saw giant lobes of radio emissions, stretching 4 million light years from end to end.

A low-frequency radio telescope like NCRA’s Giant Metrewave Radio Telescope is ideal for mapping dying radio galaxies.

“There are multiple reasons that make this galaxy so rare”.

The Galaxy was discovered using the Giant Metre Wave Radio Telescope (GMRT) which has an array of 30 fully steerable antennas which have a diameter of about 45 meters.

Those jets of hot plasma, blasting away from the black hole in opposite directions, produce huge lobes of radio emissions that can span much greater distances than the galaxy’s visible light. This then raises questions of how such an optically-sized galaxy generates multi-million light years worth of radio waves. Wadadekar said, “When we see the sun, it is a mere eight light minutes away, while the discovered galaxy is nine billion light years away”. Scientists have argued that the presence of a super massive black hole at the center of the galaxy must be fueling the large radio lobes which have been spotted.

The fading of the lobes is brought on by their dropping power in two methods, one, by emitting radio waves which present up as the large radio lobes and two, by transferring power to photons from the cosmic microwave background by way of a course of referred to as inverse Compton scattering. When this happens, the illuminating radio lobes fade away within millions of years because of inadequate resumption. Hence, it is called a giant radio galaxy.

The researchers further added that in the scientific terms all such galaxies which have an enormous radio size are known as radio galaxies.

In a new paper on J021659-044920, published this week in the Monthly Notices of Royal Astronomical Society, researchers say they’ve identified a giant radio galaxy in decline.

The recent discovery of the J021659-044920 is something extraordinary because the astronomers were able to catch it during its dying stage. Such dying radio objects are best studied using a low frequency radio telescope such as the GMRT.

The GMRT was built and is operated by National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research and has been in operation since 2002.

The device which helped spot this rare galaxy, the GMRT, is the world’s largest radio telescope facility.