Black hole discovered firing jets at neighboring galaxy

With the help of citizen scientists, a team of astronomers has discovered a unique black hole spewing a fiery jet into another galaxy.

The black hole is housed in a galaxy about a billion light-years from Earth called RAD12. The work was published in Monthly Notices of the Royal Astronomical Society: Letters.

Galaxies are typically divided into two main classes based on their morphology: spiral and elliptical. The spirals have optically blue-looking spiral arms with abundant cool gas and dust. In spiral galaxies, new stars form at an average rate of one Sun-like star per year. In contrast, elliptical galaxies appear yellowish and lack distinctive features such as spiral arms.

Star formation in elliptical galaxies is very rare. It is still a mystery to astronomers why the elliptical galaxies we see today have not been forming new stars for billions of years. Evidence suggests that supermassive black holes or “monsters” are responsible. These “monstrous” black holes spew giant jets made of electrons moving at very high speeds into other galaxies, depleting the fuel needed for future star formation: cold gas and dust.

The unique nature of RAD12 was observed in 2013 using optical data from the Sloan Digitized Sky Survey (SDSS) and radio data from the Very Large Array (FIRST Survey). However, a follow-up observation with the Giant VHF Radio Telescope (GMRT) in India was required to confirm its truly exotic nature: the black hole in RAD12 appears to be jetting only toward a neighboring galaxy, called RAD12-B. In all cases, the jets are expelled in pairs, moving in opposite directions at relativistic speeds. Why only one jet is visible from RAD12 remains a puzzle to astronomers.

A conical stalk of young plasma is seen being ejected from the center and reaches far beyond RAD12’s visible stars. GMRT observations revealed that the older, fainter plasma extends well beyond the central conical stalk and flares out like a mushroom cap (seen in red in the tricolor image). The entire structure is 440,000 light-years across, which is much larger than the host galaxy itself.

RAD12 is unlike anything known before; this is the first time a jet has been observed colliding with a large galaxy like RAD12-B. Astronomers are now one step closer to understanding the impact of such interactions on elliptical galaxies, which may leave them with little cool gas for future star formation.

Research leader Dr Ananda Hota says in a statement: “We are excited to have detected a rare system that helps us understand the feedback of radio jets from supermassive black holes on the formation of stars from galaxies during mergers. Observations with the GMRT and data from several other telescopes, such as the MeerKAT radio telescope, strongly suggest that the radio jet in RAD12 is colliding with the companion galaxy. An equally important aspect of this research is the demonstration of public involvement in making discoveries through the RAD@home citizen science research collaborative.