Dark matter is thought to make up more than 80% of all matter in the universe, but what it actually is remains a mystery.
Now astronomers have discovered something that gives us a major clue.
In two new studies published in Natural astronomy And Monthly Notices of the Royal Astronomical SocietyAstronomers report that they have found a low-mass object in the ancient outskirts of the cosmos by examining gravitational distortions in the light of a much larger galaxy.
This oddity, they claim, is the lowest mass object ever discovered using this technique, called gravitational lensing.
“It’s an impressive achievement to detect such a low-mass object at such a great distance from us,” said Chris Fassnacht, an astronomer at the University of California, Davis and co-author of the study. Natural astronomy study, said in a statement about the work. “Finding low-mass objects like this is key to learning more about the nature of dark matter.”
However, it is large: the object weighs more than a million solar masses, or more than a million times the weight of the Sun. Residing some 10 billion light years away, we observed it when the universe was only 6.5 billion years old, less than half its current age.
Despite these staggering proportions, it is the lowest mass object ever found using gravitational lensing, according to the authors – by a staggering factor of around 100.
To discover the object, the researchers combined observations from radio telescopes around the world, including the Very Long Baseline Array (VLBA) in Hawai’i and the European Very Long Baseline Interferometric Network (EVN) in Europe, to create an “Earth-sized super-telescope,” as the researchers described it. Then they had to develop algorithms specifically designed to reveal the object among the resulting mountains of data.
Since dark matter is invisible, we cannot observe it directly. But we can observe the attraction of its gravity on other objects. In fact, its gravitational influence is thought to play a key role in the existence of the largest structures in the cosmos, drawing ordinary matter around “halos,” or clusters of itself, to form galaxies and perhaps stars.
This is in any case the dominant theory described in the main cosmological framework, the lambda CDM model – CDM being the abbreviation of “cold dark matter”. Although there are many candidates for dark matter, much of the debate focuses on whether dark matter is hot or cold. Hot dark matter would be made up of lighter, fast-moving particles, and cold matter would be made up of heavier, slower-moving particles. If it’s cold and slow, it would also be “lumpy,” clumping together in halos instead of being distributed smoothly across the cosmos.
The discovery of this new dark object “is consistent with the so-called ‘cold dark matter theory’ on which much of our understanding of galaxy formation is based,” Devon Powell of the Max Planck Institute for Astrophysics, the lead author of the study. Nature paper, said in the statement. If dark matter is indeed clumped together, then we should spot halos of different sizes all over the universe.
“Having found one,” Powell added, “the question now is whether we can find more and whether their numbers will still agree with the models.”
There is, however, still some light to be shed on this dark object. Astronomers have not yet confirmed what it is; the favored explanation is that it is a dark matter halo, but it could also be an inactive but ultra-compact dwarf galaxy. However, the fact that he was spotted is an achievement in itself. “The precise measurement of its mass, size, and position is unprecedented for an object in this mass range and distance,” the authors write in the report. Nature study.
Learn more about astrophysics: The James Webb appears to have spotted a “dark star” powered by dark matter, Paper claims.
