The Hubble Space Telescope has recently discovered a long, narrow trail of stars that formed eight billion years ago, similar in size to the Milky Way. The origin of this mysterious structure has puzzled many research groups, with one initial controversial hypothesis suggesting it could be the result of a supermassive black hole passing through a gas cloud. However, other scientific teams have explored less exotic scenarios to explain the observations.
In a new study published in Astronomy & Astrophysics, researchers from the Instituto de Astrofísica de Canarias propose that the trail of stars could be interpreted as a galaxy without a bulge seen edge-on, which is a relatively common type of galaxy. The motions, size, and quantity of stars observed in this structure fit what has been seen in local galaxies. Comparing it to a well-known local galaxy without a bulge, IC5249, the team found surprising agreement in the velocities of the distant structure of stars. This new scenario is much simpler than the black hole hypothesis, but it is also a pity since the existence of fleeing black holes is expected, and this could have been the first one to be observed.
In order to support the hypothesis that the trail of stars is a galaxy without a bulge seen edge-on, the research team from Instituto de Astrofísica de Canarias compared it with a well-known local galaxy, IC5249, which has a similar mass of stars. Surprisingly, they found that the velocities of the distant structure of stars were very similar to those obtained from the rotation of galaxies. This led them to compare the two galaxies more closely, and they discovered that they were extraordinarily similar.
Further analysis revealed that the mass of the assumed galaxy and its maximum velocity of rotation were consistent with what is expected of a galaxy. Ignacio Trujillo, an IAC researcher involved in the study, notes that it is an interesting object because it is a large galaxy located at a very large distance from Earth, where most galaxies tend to be smaller.
With upcoming observations, the research team hopes to study this object in greater detail and learn more about its properties.