Rare & dying: Giant radio galaxy found 9mn light yrs away from Earth

Astronomers in India have discovered a giant radio galaxy located 9 billion light years away, which emits radio waves that extend a whopping 4 million light years. But the rare galaxy won't always have such an incredible reach, because it's dying.

The galaxy, known as J021659-044920, was found by a team of astronomers working at the National Center for Radio Astrophysics (NCRA) in Pune, India. Located towards the constellation Cetus, the galaxy was discovered using the Giant Metrewave Radio Telescope (GMRT) – the world's largest radio telescope facility operating at low radio frequencies.

While discovering a galaxy that spans 100,000 light years is certainly an accomplishment in itself, it didn't take the astronomers long to realize there was something even more extraordinary about their finding.

When the scientists looked at J021659-044920 in the radio spectrum, they saw giant lobes of radio emissions which stretched 4 million light years. This indicated that they had discovered a giant radio galaxy, an extremely rare occurrence.

The findings were published in the journal Monthly Notices of the Royal Astronomical Society.

The galaxy's ability to emit radio waves stems from a supermassive black hole at its center. As the black hole draw material toward it, the materials fall into its spiral. The motion of the charged material creates electromagnetic forces which can accelerate material away from the black hole at nearly the speed of light. Jets of hot plasma blasting away from the black hole in opposite directions create huge lobes of radio emissions.

But the astronomers won't be given much further opportunity to observe J021659-044920 in action, because it was discovered just as it was dying.

Radio galaxies die when the black hole stops producing the radio jet. The radio lobes then fade away within a few million years, due to lack of replenishment. The galaxy was at this end phase when the astronomers discovered it.

Although smaller radio galaxies spanning less than a million light years are somewhat common, only a few giant radio galaxies have ever been found.