Dark matter is, by definition, difficult to detect. What it is, how it behaves, and whether it has changed since the Big Bang are tantalizing questions for cosmologists.
Using astrophysical data from Subaru’s Hyper Suprime-Cam Survey (HSC) and the European Space Agency’s Planck Satellite, a collaboration led by scientists from Nagoya University in Japan has managed to look further into the depths of our Universe’s early dark matter than ever before, and they plan to investigate further.
Dark matter does not interact with light at all; its presence is usually inferred through its gravitational influence on matter that we can actually see (how it affects the galaxy rotation curvesfor example) – although there are some promising direct sensing experiments underfoot.
Dark matter can also be detected through a phenomenon known as gravitational lensing, in which light from a distant source, such as a galaxy, is bent and focused toward observers on Earth by an intermediate mass (such as another galaxy). or dark matter cluster). This is similar to the way curved glass lenses in eyeglasses refract or ‘bend’ light into an eyeball, only in this case, the ‘glass lens’ is a galaxy encased in a shroud of dark matter. , warping space-time in a brilliant illustration of Einstein’s Theory of General Relativity.
Because of the way gravitational lensing can focus light from a distant background source, the method has helped scientists see further into the early Universe than ever before (As one looks deeper into space, one also looks further back in time.) But in this research, the team, led by Hironao Miyatake, used the process to investigate the lens itself and contribute to understanding the evolutionary nature of dark matter.
Since light spreads in all directions when it travels from a source, it gets progressively weaker with distance. This makes it incredibly difficult to see galaxies and other objects very early in our Universe (beyond about 10 billion years ago) and, by extension, to characterize the intervening dark matter.
Miyatake and his team managed to overcome this challenge by changing the background light source, forgoing distant galaxies for the cosmic microwave background (CMB). The WBC is radiation remnants from a time shortly after the Big Bang and it is the earliest light we can see in our Universe.
Using data from the HSC, the researchers identified 1.5 million lensed galaxies at an age of about 12 billion years. They compared this to CMB observations from the Planck Satellite. This showed how dark matter around the lensing galaxies was distorting the CMB background light, and ultimately allowed the team to investigate the large-scale distribution of dark matter about 12 billion years ago, further back in time. the time of what has been achieved so far.
“For the first time, we were measuring dark matter from almost the earliest moments of the universe,” said assistant professor Yuichi Harikane of the University of Tokyo’s Cosmic Ray Research Institute.
Why does dark matter matter, anyway?
Despite the fact that we still do not confidently understand the nature of this mysterious matter responsible for more than five times the matter we see around us, dark matter is intrinsically intertwined with the physical composition and behavior of our Universe. A popular model of the nature of dark matter, the Lambda-CDM model, predicts some level of clumping of dark matter in the early Universe. These clusters gravitationally attract other matter, including visible matter, leading to the gradual formation of the stars, galaxies, and clusters we see today.
The researcher’s preliminary findings indicate that dark matter 12 billion years ago was less clumpy than current cosmological theory predicts, perhaps hinting at the possibility that it behaved differently in the early Universe.
Miyatake says that if the early Universe is less clumpy than we thought, we may need to rethink our theories of physics: “Our finding is still uncertain. But if true, it would suggest that the entire model is flawed as you go back in time. This is exciting because if the result holds after uncertainties are reduced, it could suggest an improvement to the model that can provide insights into the nature of dark matter itself.”
Looking ahead, Miyatake and the team plan to delve further into the past, finishing the final two-thirds of their HSC dataset and potentially analyzing advanced datasets like the Vera C Observatory’s Legacy Survey of Space and Time (LSST). Rubin. “LSST will allow us to observe half the sky,” said Harikane. “I don’t see any reason why we can’t see the distribution of dark matter 13 billion years ago.”