A few years ago, astronomers discovered a large structure of dwarf galaxies and star clusters with an unusual configuration that suggested it might violate the standard cosmological model. This had some researchers even state that dark matter might actually be wrong.
A new study, accepted in the Monthly Notices of the Royal Astronomical Society, claims that the configuration, the so-called vast polar structure (VPOS), is not a problem for dark matter because it’s all about how it came to form.
The standard model expects structures to be equally distributed in the universe. Therefore, the VPOS, which has small galaxies aligned in a plane perpendicular to the Milky Way disk, looks a bit fishy. The team discovered that the VPOS is actually transient and the galaxies did not form there, they are just passing by – this a quirk of the model rather than a violation.
“If the planar structure lasted for a long time, it would be a different story,” senior author Professor Sukanya Chakrabarti, from the Rochester Institute of Technology, said in a statement. “The fact that it disperses so quickly indicates that the structure is not dynamically stable. There is really no inconsistency between the planar structure of dwarf galaxies and the current cosmological paradigm.”
The team looked at how these satellites move and created simulations to see how the structure evolved over time.
“We tried many different combinations of the dwarf galaxies, including distributions of dwarfs that share similar orbits, but in the end found that the plane always dispersed very quickly,” lead author Andrew Lipnicky, a Ph.D. candidate at Rochester Institute of Technology, added.
The VPOS has never been conclusive proof of something wrong with dark matter and it definitely didn’t rule it out. Nevertheless, it was necessary to check it out. The standard model tells us of an ideal universe that, on average, looks the same in every direction. But once you stop looking at the average and you enter into the nit and grit of single galaxies, things may not be as neat.