The galaxy NGC 6240 has a unique feature: a massive cloud of gas shaped like a butterfly. Unlike the relatively tidy disk of the Milky Way, jets and bubbles of gas shoot off from NGC 6240 giving the galaxy the appearance of a butterfly in flight.

Galaxy With Two Supermassive Black Holes At The Center

Most known galaxies tend to have only one supermassive black hole at the center but the galaxy NGC 6240 is different in a way that it contains two. Scientists think these galaxies form from the merger of twin galaxies.

The two black holes also circle each other in a final stage of a merger. The merger process has triggered dramatic star formation and numerous supernova explosions. Scientists believe that the merger will be completed within tens to hundreds of millions of years.

Francisco Müller-Sánchez, from the University of Colorado Boulder, and colleagues took a closer look at NGC 6240 and discovered what causes the star formation in the galaxy to slow down.

Slowing Down Star Formation In NGC 6240

In their new study, which was published in the journal Nature on April 18, Müller-Sánchez and colleagues suggested that gases produced by the two spiraling black holes, along with the gases expelled by the stars in the galaxy, may have started to slow down NGC 6240's ability to produce new stars.

The researchers found that two different forces formed the nebula. The northwest corner of the butterfly is the products or stellar winds, the gases that stars emit. The northeast corner is dominated by a single cone of gas ejected by the two black holes as they gobble up massive amounts of galactic gas and dust during their merge.

"Here we report observations of dual outflows in the central region of the prototypical merger NGC 6240. We find a black-hole-driven outflow of [O III] to the northeast and a starburst-driven outflow of Hα to the northwest," the researchers wrote in their study.

Together, the two winds eject massive amounts of gases from the galaxy equivalent to about a hundred times the mass of the sun each year, which has implications for the galaxy. Clearing away gases needed for the formation of new stars slows down new star formation.

"It is forming stars intensely now, so it needs the extra strong kick of two winds to slow down that star formation and evolve into a less active galaxy," said study researcher Julie Comerford, from CU Boulder.