The current view states that the universe is filled with mysterious dark matter and dark energy. Models using them make accurate predictions of the state of the universe, although they are not perfect. For example, they suggest the presence of a large number of dwarf galaxies out there, but when we look out into the sky, we find a much smaller amount.
This "dwarf galaxy problem" has been a thorn in the side of the cosmological model for years, but new research published in Nature Astronomy has found evidence that may solve the conundrum. It appears that dwarf galaxies form groups independent of larger galaxies and these groups are likely to merge into a single medium galaxy within 1 billion years. That's why we can't seem to see them anymore.
The international team of astronomers has discovered seven isolated dwarf galaxy groups, with each hosting three to five members. These were part of the TiNy Titans (TNT) survey that’s investigating how dwarf galaxies interact with each other.
The TNT dwarf groups allowed the researchers to look into how structures form at the low-mass end of cosmic structures. The researchers hope to spot tendrils of gas stretching within the group to prove that most of these dwarf galaxies are interacting.
The objects are between 10 to 1,000 times smaller than our own Milky Way and are located between 200 and 650 million light-years from us. This is very close in cosmic terms, but too dim for us to find further groups yet.
Upcoming observatories like the Large Synoptic Survey Telescope and the James Webb Space Telescope plan to observe further and dimmer objects. This will be a crucial test for these systems. Astronomers think that dwarf galaxy groups were common in the early universe, but became rarer and rarer due to merging.
This is all, of course, on the assumption that dark matter truly exists. On cosmic scales, the properties of dark matter have been extensively tested and there is a pretty compelling argument. While we know what it does, we are yet to find evidence of what dark matter actually is, so the field is quite open. But if issues like the dwarf galaxy problem can be explained, alternative hypotheses will have a tougher case to fight.