But astronomers have promisedto leave no stone unturnedand have started to cast their net wider out into the galaxy.
The masses of these clumps fall on a spectrum, with lower mass ones expected to be more numerous.
Is there a limit to how light they could be?
It depends on the nature of dark matter particles.
We know it exists because we can see the gravitational effects it has on the surrounding matter.
There aredifferent theoriesabout what dark matter may actually be.
This would be consistent with it being made up of particlesknown as axions or WIMPS.
Another theory, however, suggests it is warm, meaning it moves at higher speeds.
One such particle candidate is thesterile neutrino.
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Artists impression of the expected dark matter distribution around the Milky Way, seen as a blue halo.
If dark matter is warm, haloes lighter than around 108Suns cannot form easily.
So tallying light mass dark haloes can tell us something about the nature of dark matter.
A galaxy cluster with dark matter mapped in blue and bright X-rays in pink.
Dark matter haloes can also affect how light bends around astrophysical objects in a process calledgravitational lensing.
But the signals left in the stellar distributions are weak and prone to confusion with the stars own motions.
Another way to probe the effect of haloes is by looking at the galactic gas it affects.
Over the next few years, this new method can be used to test models of dark matter.
If the numbers match up, the standard cosmological model would have passed an important test.
Dark matter remains a mystery, but theres a huge amount of work going into solving it.
This article is republished fromThe ConversationbyAndreea Font, Astrophysicist,Liverpool John Moores Universityunder a Creative Commons license.
