'Runaway black hole,' or sneaky galaxy in disguise? Experts are conflicted.

According to a recent research, the strange stream of stars flowing across space may not be caused by a renegade black hole.

Astronomers are perplexed by a mystery starburst that appears to be flowing through space like a giant cosmic river. Is it a "renegade" black hole tearing across space, or is it actually a strangely flat galaxy? The latter is supported by recent studies, although the riddle is far from being solved.

It is believed that the cosmic streak, which was first spotted by NASA's Hubble Space Telescope, measures 200,000 light-years in length, or roughly twice the Milky Way's diameter. The streak may have been caused by a runaway supermassive black hole slicing through a cloud of star gas and dust around 7.5 billion light-years from Earth, according to a study published in The Astrophysical Journal Letters last month.

The scientists hypothesized that the object's gravity and velocity would have ignited the gas and left a path of blazing stars in its wake. A rogue supermassive black hole is an entity that is supposed to roam the universe after being evicted from its host galaxy, maybe as a result of collisions with other black holes. This thrilling finding would represent the first sighting of one.

The strangely thin streak may simply be a flat galaxy seen from its edge, much like the rim of a plate, according to the new study, which was published in the journal Astronomy & Astrophysics. The Milky Way has a bulge of stars in its core, but this hypothetical galaxy, which is known as a thin or flat galaxy, would be completely flat.

The authors of the study compared the in issue stars to a well-known flat galaxy dubbed IC5249, situated around 100 million light-years from Earth, to corroborate their interpretation. They discovered that the stars' masses and velocities in the two objects agreed.

They are "extraordinarily similar," said Mireia Montes, a co-author of the new study and an astronomer at the Canary Islands Institute of Astrophysics (IAC), in a release.

Even the researchers of the study are slightly dismayed by this result.

Jorge Sánchez Almeida, an astronomer at the IAC and the study's primary author, said in a statement, "In some ways, it is also unfortunate." He said that it would have been thrilling for the scientific world to see the first black hole to vanish.

The 'runaway' black hole may be saved

The primary author of the original runaway black hole article and Yale University professor of physics and astronomy Pieter van Dokkum is not persuaded by the new explanation. Van Dokkum pointed out various aspects of the streak findings that contradict the galaxy concept in a response article that was published on April 29 to the preprint service arXiv.org.

One thing that supports the idea that the streak was produced by a fast-moving object, such as a supermassive black hole, being ejected from the compact galaxy's center, he wrote, is that observations of the streak in far-ultraviolet wavelengths show that the stellar stream is directly connected to a nearby compact galaxy. There should be a distinct heat signature where the two galaxies converge if the streak was really a flat galaxy.

The leading edge of the runaway black hole would be just where observations also reveal a stunningly bright "knot" of ionized gas, according to van Dokkum. This lends even more credence to the black hole idea, which is not taken into consideration by the edge-on galaxy theory.

The IAC team acknowledged in the statement that the streak is also exceptionally big for a galaxy that is so far away from Earth.

Van Dokkum wrote in an email to Live Science, "We can very nearly rule out an edge-on galaxy, while there may be alternative reasons for the streak.

Whatever the answer, it is important to keep researching this unique celestial river. This summer's next Hubble observations of the streak "should be definitive" in terms of supporting or refuting the galaxy concept, according to van Dokkum. He continued by saying that the enigmatic stripe has also been chosen for upcoming studies by the powerful James Webb Space Telescope, which would search for clear signs of black holes nearby.