The runaway black hole riddle solved

El reciente hallazgo de unos investigadores del Instituto de Astrofísica de Canarias desmonta la interpretación original en donde un agujero negro supermasivo a la fuga habría dejado un rastro de estrellas a su paso

A study carried out by a research team from the Instituto de Astrofísica de Canarias (IAC) reveals that an unusual and thin star structure, recently discovered by the Hubble Space Telescope, could be a galaxy seen edge-on. The finding dismantles the original interpretation that a supermassive black hole on the run would have left a trail of stars in its wake. The results are published in the journal ‘Astronomy and Astrophysics Letters’.

A mysterious trail of stars formed eight billion years ago and recently discovered by the Hubble Space Telescope has kept numerous research teams in check. With a size similar to that of our Milky Way, this enormous and narrow structure has given rise to numerous speculations about its origin.

According to a first hypothesis, this trail of stars could be the result of the passage of a supermassive black hole through a huge cloud of gas. This assumption immediately fired the imagination of the astronomical community, as it requires a large number of very complex and exceptional circumstances to occur simultaneously. For this reason, different scientific teams have continued to explore different less exotic scenarios capable of explaining what has been observed.

In a recent work, IAC researchers have concluded that this unusual star structure can be interpreted as a bulgeless galaxy seen edge-on. These types of galaxies, also called thin or flat galaxies, are relatively common.

“The movements, size and number of stars match what has been seen in the galaxies of the local universe”, explains Jorge Sánchez Almeida, IAC researcher and first author of the article. “It’s a huge relief to have solved the mystery; the proposed new scenario is much simpler. In a sense it’s also a shame because we expect runaway black holes to exist, and this could have been the first to be observed.” , Add.

To support the galaxy hypothesis, the scientific team compared the enigmatic structure with a known local bulge galaxy, IC5249, which has a similar stellar mass, and found a striking agreement. In the words of Mireia Montes, a researcher at the IAC and co-author of the study, “when analyzing the speeds of this distant structure of stars, we realized that they were very similar to those obtained by the rotation of galaxies, so we decided to compare with a closer one and we notice that they are extraordinarily similar”.

“We also explored the relationship between the mass of this supposed galaxy and its maximum speed of rotation, and we discovered that it is indeed a galaxy acting like a galaxy,” says Ignacio Trujillo, an IAC researcher who has participated in the study. “It is a very interesting object since it is a fairly large galaxy at a very distant distance from Earth where most of the galaxies are smaller,” he adds.