Astronomers have discovered an extremely faint, low-mass object in the distant cosmos, raising suspicion that it could be made up of dark matter, the elusive substance that makes up nearly 30% of the universe.
The team claims this may be the lowest-mass dark object ever found in the universe, but they haven’t yet been able to determine the nature of this mysterious discovery. Too faint to be seen, the object was found using gravitational lensing, which works by measuring the effect of an object’s gravity on light passing around it.
“Finding low-mass objects such as this one is critical for learning about the nature of dark matter,” study coauthor Chris Fassnacht, professor in the Department of Physics and Astronomy at the University of California, Davis, said in a statement.
The discovery, detailed in a study published Thursday in Nature Astronomy, could help scientists unravel some of the many mysteries surrounding dark matter.
Cosmic mystery
For this study, the scientists combined the powers of several observatories to create the equivalent of an Earth-sized telescope, sensitive enough to be able to detect such a small object. Gravitational lensing is the universe’s magnifying glass, and the newly discovered object is so small that it appeared to cause a tiny distortion on the gravitational lens of a distant galaxy.
“It’s an impressive achievement to detect such a low mass object at such a large distance from us,” Fassnacht said.
The object’s true nature is still unknown, but the researchers believe it could be a sign of dark matter, or, possibly, a very small and compact dwarf galaxy. Dark matter is the glue that holds the universe together, making up around 27% of all matter in the cosmos, according to NASA. But despite its abundance, it is invisible to our eyes (hence the name), and its existence is inferred by the effect it has on surrounding, ordinary matter.
Shining light on dark matter
Dark matter makes up most of the mass in galaxies and galaxy clusters, and while it doesn’t interact with light, its gravity can bend the light from distant galaxies to create a gravitational lens. If this object is composed of dark matter, then it is 100 times smaller than any other clump of dark matter ever detected.
The researchers note that the new discovery is consistent with a particular hypothesis known as cold dark matter theory, which suggests that dark matter is made up of weakly interacting, slow-moving particles that clump together by way of gravity.
“Given the sensitivity of our data, we were expecting to find at least one dark object,” Devon Powell at the Max Planck Institute for Astrophysics (MPA), Germany, and lead author of the paper, said in a statement. “Having found one, the question now is whether we can find more and whether the numbers will still agree with the models.”