Imma Perfetto
Cosmos science journalist
Astronomers may have detected a clump of dark matter 100 times smaller than any found so far. Alternatively, they suggest it could also be an ultracompact, inactive dwarf galaxy.
The mysterious object, which has a mass of about 1 million times that of the Sun, was detected by the way its gravity distorts light passing through or near it in a phenomenon called ‘gravitational lensing’.
This caused a small pinch to occur in the gravitational lensing caused by a much larger, distant galaxy.
“It’s an impressive achievement to detect such a low mass object at such a large distance from us,” says Chris Fassnacht, professor in the department of physics and astronomy at the University of California Davis in the US.
“Finding low-mass objects such as this one is critical for learning about the nature of dark matter.”
The Standard Model of Cosmology, called the ‘Lambda cold dark matter’ model, is the simplest model which explains the universe.
According to this model, ordinary matter only makes up about 5% of the Universe. Dark matter, which doesn’t absorb, emit or reflect light, but does have gravity, should make up about 27% of the Universe to explain the way gravity clumps together galaxies and galaxy clusters.
“Given the sensitivity of our data, we were expecting to find at least one dark object, so our discovery is consistent with the so-called ‘cold dark matter theory’ on which much of our understanding of how galaxies form is based,” says Devon Powell from the Max Planck Institute for Astrophysics (MPA), Germany.
“Having found one, the question now is whether we can find more and whether the numbers will still agree with the models.”
The research is described in 2 papers published in Nature Astronomy and Monthly Notices of the Royal Astronomical Society.