Ralf Kaehler / SLAC National Accelerator Laboratory / AMNH
Simulation of the formation of dark matter structures from the beginning of the universe to the present day
Boson stars, Q-balls. Dark, exotic astrophysical objects may be hiding in interstellar space, and a new proposal suggests how to find them: look very, very carefully.
Searches for dark matter particles have so far resulted in failure, leading theorists to be increasingly more creative in their proposals.
We don’t know what the dark matteralthough we strongly suspect its existence. We found clues circumstances everywhere, from the rotation speeds of galaxies to the growth of the largest structures in the cosmos.
For decades, cosmologists thought dark matter was some kind of exotic particlepreviously unknown to the Standard Model of particle physics.
This strange particle would not interact with lightnor with practically anything else, except through your gravitational influenceexplains .
Searches for these dark matter particles continue to come up empty, leading theorists to look for more imaginative ideas. It may be that dark matter is not made up of trillions of tiny particles flying around the universe. Instead, it may be formed by clusters of much larger objects.
In a new, recently pre-published in arXivresearchers analyzed two types of exotic objects.
The first is known as boson star. In this model, dark matter is composed of a ultralight particlepotentially millions of times lighter than neutrinos, the lightest particles known.
These particles they would be so light that their quantum nature would make them behave more like waves on a galactic scale rather than as individual particles. However, these waves sometimes they would group together and accumulatecoming together by its own gravity, without collapsing.
Another possibility is the so-called Q-balls. In this model, dark matter is not a particle, but rather a quantum field that permeates all space and time. Due to a special property of this field, it could occasionally form large, stable, ball-like clumps that drift through the cosmos like a lump of flour floating in a poorly mixed sauce.
Both boson stars and Q-balls, which fall into the more general category of Exotic Dark Astrophysical Objects (EADO)are difficult to detect. They are large — with dimensions comparable to those of stars — but they do not emit their own light, making them practically invisible in our observations of the cosmos.
However, astronomers have discovered a way for EADOs to reveal their presence: the gravitational microlensing.
If a Q-ball or boson star passed between us and a distant star, the strong severity of EADO would cause the light from this star to act as a gravitational lens. From our perspective, it would appear that the star suddenly jumped in position and then quickly returned to normal.
That’s why, all we would have to do was watch a large number of stars for a long time and hope to be lucky.
Fortunately, we have exactly the right instrument for the job. The mission was precisely this: to observe an enormous number of stars over a long period.
The astronomers responsible for the study propose using the Gaia data to look for Q-balls and boson stars, analyzing their characteristic sign and unequivocal: sudden jumps in the position of the stars. Depending on the existing quantity, Gaia may have already detected up to several thousand EADOs.
But if they don’t exist, this same analysis will allow us to place strict limits on the contribution of Q-balls and boson stars to the overall dark matter picture. Regardless of the outcome, looking into the dark will always teach us something.
