Discovery of a black hole firing jets at the nearby galaxy

With the help of citizen scientists, a team of astronomers has discovered a unique black hole spewing a jet of fire towards another galaxy. The black hole is hosted by a galaxy about a billion light-years from Earth named RAD12. The book was published today in Royal Astronomical Society monthly notices (letters).

Galaxies are generally divided into two major classes based on their morphology: spirals and ellipticals. The spirals have optically blue spiral arms with an abundance of cold gas and dust. In spiral galaxies, new stars form at the average rate of one Sun-like star per year. In contrast, elliptical galaxies appear yellowish and lack distinct features such as spiral arms.

Star formation in elliptical galaxies is very rare; it’s still a mystery to astronomers why the elliptical galaxies we see today haven’t formed new stars for billions of years. Evidence suggests that supermassive or “monstrous” black holes are responsible. These “monstrous” black holes spit out gigantic jets of electrons moving at very high speed towards other galaxies, depleting the fuel necessary for the future formation of stars: 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 needed to confirm its truly exotic nature: the black hole in RAD12 appears to eject the jet only towards a nearby galaxy, named RAD12-B. In all cases, the jets are ejected in pairs, moving in opposite directions at relativistic speeds. Why a single jet is seen from RAD12 remains a mystery to astronomers.

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

RAD12 is unlike anything known so far; it is the first time that a jet has collided with a large galaxy like RAD12-B. Astronomers are now on the verge of understanding the impact of such interactions on elliptical galaxies, which could leave them with little cold gas for future star formation.

Dr Ananda Hota, lead researcher, says: “We are delighted to have spotted a rare system that helps us understand the feedback of radio jets from supermassive black holes on the star formation of galaxies during mergers. Observations with the GMRT and data from various other telescopes such as the MeerKAT radio telescope strongly suggest that RAD12’s radio jet is colliding with the companion galaxy. An equally important aspect of this research is the demonstration of public participation in making discoveries through the [email protected] Citizen Science Research Collaborative.”

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Materials provided by Royal Astronomical Society. Note: Content may be edited for style and length.