In a "Hubble" image, a research team discovers a strange trace. It turns out to be a 200,000 light-year long chain of young blue stars. © NASA, ESA, Pieter van Dokkum (Yale); Image Processing: Joseph DePasquale (STScI)
A black hole that has been ejected from its galaxy and has a trail of stars behind it - this interpretation of a phenomenon in space is apparently not correct.
At the beginning of April, a research team led by astronomy and physics professor Pieter van Dokkum of Yale University reported a phenomenon in space: A narrow, straight strip of newly formed stars, far away from any galaxy, was imaged by the Hubble Space Telescope. A research group led by van Dokkum took up the matter and put forward a theory, which was also published in the journal Astrophysical Journal Letters.
The theory: A supermassive black hole has been ejected from its home galaxy and is trailing a trail of new stars on its way through space. "Nothing like this has ever been seen anywhere in the universe," van Dokkum explained after the study was published. However, there must be numerous exceptions to the theory of the research group - which is why other research teams investigated the facts further. A new study, published in the journal Astronomy and Astrophysics, now comes to a completely different conclusion. "Despite the undeniable interest in this idea, the actual physical interpretation is not without difficulties," the research group writes.
New study: A "fleeing" black hole becomes a galaxy
"The motions, size and number of stars match a galaxy in the local universe," explains Jorge Sanchez Almeida of the Instituto de Astrofísica de Canarias (IAC) in a statement. Almeida is the lead author of the study, which has found a simpler explanation for the phenomenon observed by Hubble. "We offer a more conventional explanation: the stellar tail is a galaxy seen from the side without a bulge," the study said. Study leader Almeida is pleased with the explanation: "It is a relief to have found the solution to this problem. The new, proposed scenario is much simpler."
Comparison: The mysterious star trail in space and the view of the galaxy IC5249. © HST
Earlier, Almeida's team compared the mysterious structure in the universe to IC5249, a well-studied galaxy without a bulge that has a mass of stars similar to that of the mysterious star trail in space. To everyone's surprise, the research group found a consensus. "When we analysed the velocities of this distant stellar structure, we found that they were very similar to those from the rotation of galaxies," explains co-author Mireia Montes. So they decided to compare a much closer galaxy and found that they are "extraordinarily similar".
Universe: "A galaxy that behaves like a galaxy"
The relationship between mass and maximum rotation speed also suggests that the unusual structure "is a galaxy that behaves like a galaxy," according to Ignacio Trujillo, who was also involved in the study. "It's an interesting object because it's a relatively large galaxy, very far from Earth," Trujillo explained. In the vicinity of Earth, the majority of galaxies are smaller. (tab)